Air Conditioners Will Heat Your Home Cheaper Than Gas. Here’s Why.

Reverse cycle air conditioner vs gas heating

The best way to heat your home is with a reverse cycle air conditioner.  This is true whether your goal is to save money or save the planet.  In this article, I’ll explain no matter how crap your air conditioner is, you’re likely to be financially better off using it for heat instead of gas.

Depending on where you are and the efficiency of your air conditioner, it’s possible to cut your heating bills by more than half.  The greatest savings are in Western Australia.  Thanks to having Australia’s highest gas prices and lowest solar feed-in tariff, in Perth a solar-powered air conditioner can provide heat at under 7% the cost of gas.

I’m only going to offer economic and environmental reasons for using air-con heating.  If you just happen to love the smell of gas in the morning, I can’t help you1. Feel free to critique my savings analysis in the comments, but if you’re simply in love with methane, please try very hard to keep it a secret love. 

In this article, I’ll cover:

  • The efficiency of gas heating.
  • How modern air conditioners can easily be 5 times more efficient than gas.
  • The cost of heating with gas compared to reverse cycle air conditioners.
  • Why you’d have to be nuts not to use an air conditioner for heat in Perth.

Once you’ve read that, you’ll see — while Jumping Jack Flash may be a gas, gas, gas — what you’ll really want to keep your home warm, warm, warm, is an efficient reverse cycle air conditioner. 

Gas Efficiency Under 90%

Heating with gas is very straightforward.  Flammable natural gas is piped into your home where it’s set on fire — preferably inside some sort of heater — and releases heat.  Unless a gas heater is dangerously defective, the heater will convert all the chemical energy in the gas into heat energy.  Even all the light it gives off will end up as heat in your home if you shut the curtains.  This may make gas heating seem like it should be 100% efficient, but in practice it’s not.  Natural gas heaters often only have an efficiency of around 70%. 

There are some minor reasons why it’s not 100%.  Gas in winter can be cold when it enters your home, and its pipe can conduct heat out.  But the main reason is ventilation. 

There are two basic types of gas heaters:

  • Flued, and…
  • Unflued. 

A flued gas heater has not come down with a virus.  It means it has a chimney or other dedicated ventilation that allows carbon dioxide and water vapour from combustion to escape outside.  Unflued heaters are potentially more efficient, but if you try to make them very efficient by sealing the room, they will kill you.  Because of this danger, unflued heaters are restricted in how much gas they can burn and rooms they are in are required to have ventilation.  Exact requirements can vary from state to state. 

A flue allows heat to escape, and room ventilation does the same.  This results in the efficiency of gas heaters being as low as 60%.  The average efficiency of existing heaters may be 70-80%.  The highest efficiency for a correctly installed gas heater that meets state and Australian standards may be 90%.   

Gas Is A Health Hazard

Natural gas is mostly methane.  When burned this releases carbon dioxide (CO2) and water vapour.2  The CO2 from an unflued gas heater is not good for your health. If the heater is defective, it can produce carbon monoxide that your body can’t detect and which can harm or kill you.  For this reason, it’s recommended to have gas heaters regularly serviced and not to place them in bedrooms.

If you don’t believe me, watch this disturbing Irish cartoon:

Water vapour from burning gas can also be a problem.  While a little humidity can be nice in winter, too much can lead to dampness, mould, and mini-waterfalls of condensation running down your windows.   

Reverse Cycle Air Conditioner Heating Efficiency

Only air conditioners that are ‘reverse cycle’ can provide heat.  Instead of only pumping heat out of your home and cooling it, they can reverse the cycle and pump heat from the outside air into your home.  Most air conditioners on sale are reverse cycle but don’t accidentally buy one that only cools.  

Air conditioners are far more efficient at heating than gas because, instead of using energy to create heat directly, they use energy to move heat around. As a result, even the worst air conditioner you can buy is several times more energy-efficient than using gas.  

Because air conditioners pump heat around, they’re called heat pumps.  If you want to know how to choose an energy-efficient one, I recently wrote an article on how the new air conditioner labelling system works.  I recommend getting the most efficient reverse cycle air conditioner you can find that doesn’t have a ridiculous price tag designed to suck in rich hippies. 

Recommendation - reverse cycle air conditioner vs. gas for heating

But even the worst air conditioner you can buy will provide around 3.5 kilowatt-hours of heat for every kilowatt-hour of electricity consumed, giving them an effective energy efficiency of around 350% and four or more times as efficient as a typical gas heater.

Kilowatt-Hours And Megajoules

Electricity is sold by the kilowatt-hour.  In normal conversation, “kilowatt-hour” refers to electrical energy, but it can be any kind of energy including heat.  If you use one kilowatt-hour of electricity in a basic electrical resistance heater like one of these…

electrical resistance heaters

Don’t turn these on when they’re sitting on a red cushion unless you’re eager to see orange flames.

…it will convert that electrical energy into one kilowatt-hour of heat energy.  But an air conditioner with 3.5 Energy Stars for heating will pump a minimum of 5 kilowatt-hours of heat energy into your home for every kilowatt-hour of electricity it consumes.  This makes it at least 500% efficient.   

Gas is paid for by the megajoule (MJ).  This is just a different measure of energy.  For easy comparison, I will convert megajoules into kilowatt-hours.  It’s not difficult to do as there are simply 3.6 megajoules in a kilowatt-hour. 

Gas Supply Charge Not Included

I am not considering the daily supply charge when determining the cost of gas.  This charge, along with the cost of regularly servicing gas appliances to maintain safety, is an excellent reason to stop using gas entirely. 

Cost Of Gas By Capital

I’ve looked online to find the lowest cost gas plans in each capital.  Except for Darwin.  If you heat your home there all I can say is…

“Welcome to the planet Earth and enjoy your stay.  Please don’t try to convince the locals the place would be better with more greenhouse gases in the atmosphere.”

With most gas retail plans, the cost per megajoule falls once consumption exceeds a threshold.  To work out the average cost of gas for a household, I’ll need to decide how much it consumes.  Most Australian households use around 30 megajoules or less per day in winter, but in Victoria, it is nearly 100.  To keep things easy, I will base the cost of gas on households using 100 megajoules a day. 

In Tasmania, they average over 200 megajoules a day in winter, but they pay a flat price for gas, so what they’re charged doesn’t change with the amount used.

The average cost of the cheapest gas I could find in all state capitals and Canberra3, in megajoules and kilowatt-hours, is:

Update August 30th 2021: I made a stupid mistake with the gas price for Perth.  In the other states gas is sold by the megajoule but in WA it’s by the kilowatt-hour.  I didn’t realize this, so the price I gave for gas there was 3.6 times higher than it should have been.  I’ve corrected all the references to Perth gas prices in the article.   

  • Adelaide:  3.2 cents per megajoule,  11.6 cents per kilowatt-hour
  • Brisbane:  4.1 cents per megajoule,  14.8 cents per kilowatt-hour
  • Canberra:  3.5 cents per megajoule,  12.6 cents per kilowatt-hour
  • Darwin:  Don’t be silly
  • Hobart:  4 cents per megajoule, 14.4 cents per kilowatt-hour    
  • Melbourne:  1.5 cents per megajoule,  5.6 cents per kilowatt-hour
  • Perth:  1.9 cents per megajoule,  6.9 cents per kilowatt-hour
  • Sydney:  2.2 cents per kilowatt-hour,  8.1 cents per kilowatt-hour

Here’s a graph comparing the per-kilowatt-hour cost of gas with the per-kilowatt-hour cost of grid electricity4 in each (sensible) capital:

As you can see, a kilowatt-hour of gas is always cheaper than a kilowatt-hour of grid electricity.  In Adelaide, Melbourne, and Sydney gas is under one-third the cost of grid electricity.  Even in Perth, which has the most expensive gas, an efficient gas heater will still be cheaper to run per kilowatt-hour of heat output than an electric resistance heater. 

So thank goodness everyone reading this is smart enough to use an air conditioner for heat rather than some dinky, little, electric resistance heater.

Resistance heater

Gas Heating Vs. Air Conditioner — Almost Worst Case

Twenty years ago, it was possible to buy a reverse cycle air conditioner so inefficient it would only move 2 kilowatt-hours of heat into your home for every kilowatt-hour of electricity consumed.  But for 10 years, the minimum efficiency level has been roughly 350%. Of course, this isn’t an exact figure. It will depend on the air conditioner’s characteristics and where it’s installed, but any air conditioner under 10 years old is likely to provide at least three times as much heat energy as it uses in electrical energy. 

Comparing a gas heater with an unrealistically high efficiency of 90% to an air conditioner with a low 300% efficiency gives the following:

Even in almost a worst-case scenario for an air conditioner under 10 years old, they always provide heat at a lower cost than gas — except in Perth.  

Gas Heating Vs. Air Conditioner — Realistic Case

In reality, most people’s choice won’t be between the most efficient natural gas heater possible and the least efficient reverse cycle air conditioner on the market.  If we instead compare a gas heater with a more typical efficiency of 75% with an air conditioner that has — going by the new energy labels — 3.5 Energy Stars out of 10 for heating, the results look far better for air conditioners.  A 3.5 star rating means the air conditioner will have an effective efficiency of at least 500%:

As you can see, with this more realistic comparison, air-con heating is way cheaper than gas.  Even in Perth air conditioner heating is under two-thirds the cost of gas. 

While you may have to pay more for a reverse cycle air conditioner with 3.5 Energy Stars than one with only a couple, the extra cost shouldn’t break the bank and there are many available with this many stars or more. 

Time-Of-Use Tariffs & Heating

So far, I’ve only shown the cost of grid electricity on a flat tariff.  With a time-of-use tariff, electricity costs can be considerably higher during peak periods.  But this is not necessarily a problem for the cost of air-con heating.  Because it’s possible to be flexible with heating, a time-of-use tariff can reduce costs.

Every air conditioner I’ve ever met has had a built-in timer5.  This makes it easy to warm your home before the start of a time-of-use peak period. Then, if you want to reduce electricity use further once the peak period starts, you can turn the thermostat down or turn the air conditioner off entirely. 

Solar Power Saves On Air-Con Costs

Having rooftop solar panels will further improve savings if you use air conditioner heating during the day.  This is because savings on electricity bills increase when you consume your own solar energy rather than grid energy — except for some households that have old, high, solar feed-in tariffs locked in.

If you’re out during the day, solar may not lower your cost of heating, but you can try setting a timer so your reverse cycle air conditioner warms your home using solar energy before you get home in the evening.  But your home is really drafty and bad at retaining heat, this may not help. 

Air-Con Emissions Less Than Gas

Sometimes natural gas salespeople will claim it’s a low emission choice for heating, but this only applies when it’s compared to electrical resistance heating.  Even an air conditioner entirely powered by coal can result in lower emissions than those that directly result from burning gas for heat, as the following three steps show:

  • Burning methane in a 75% efficient gas heater to provide one kilowatt-hour of heat will produce 237 grams of CO2 from combustion.
  • In Australia, coal power emits around 1 kg of CO2 per kilowatt-hour of electricity generated. 
  • An air conditioner with 3.5 Energy Stars for heating is at least 500% efficient and would produce around 200 grams of CO2 or less if entirely powered by coal.

Fortunately, our grid generation is only about 62% coal, and CO2 emissions per kilowatt-hour of electricity are likely to be around 656 grams.  This means, when powered by the grid, even the worst air conditioner you can buy these days will result in lower emissions than burning natural gas. 

The emissions advantage of grid powered air conditioners will improve as fossil fuel is driven from the electricity market.  Emissions from natural gas will remain much the same6.

Emissions from natural gas are even worse than they appear because additional greenhouse gas emissions occur from its extraction, refining, and distribution.  Some of this is from leaks, which is a major problem because methane is a greenhouse gas around 32 times more powerful than CO2.  There are disputes over how much fugitive emissions amount to, so I don’t have a definite figure.  But it looks to me they could easily increase greenhouse gas emissions from domestic gas by over a quarter. 

Hobart Best For Overall Savings

Brisbane is the capital is with greatest savings per kilowatt-hour of heat provided by a grid powered air conditioner.  But because Tasmanians use far more heat overall, Hobart will the capital with the greatest total savings overall.  

Perth is the best location for powering an air conditioner from solar thanks to having the lowest solar feed-in tariff in the nation, so it can cost very little to heat with an air conditioner during the day.  A WA home receiving the low DEBS solar feed-in tariff using a reverse cycle air conditioner powered by solar with an efficiency of 500% will pay less under 7% the cost of gas before 3:00 pm.  After that, it will increase to around 22% the cost of gas, but that’s still pretty good. 

Air Conditioner Heat Beats Gas

No matter how old your reverse cycle air conditioner is, you’re likely to be financially better off using it for heat than gas.  The only exceptions if you’re in Perth or Melbourne and your air conditioner is both old and one of the more inefficient ones ever sold.  But if you have solar panels and sometimes heat your home during the day, you can be confident you’ll save money no matter how crap your air conditioner may be.


  1. Warning: Methane — the main component of natural gas — is odourless.  You can only smell it in domestic gas because stinky methanethiol gas is added to it.
  2. Using bottled LPG, there will be more CO2 and less water vapour because LPG contains more carbon and less hydrogen.
  3. Note that just because I have given a price for piped gas in a city, it doesn’t mean gas will be available everywhere in that city.  For example, in Hobart, the piped gas network is quite limited.
  4. The grid electricity prices are from low-cost electricity plans for solar households that were the best I found.  A non-solar household may be able to find a slightly cheaper plan.
  5. In the old days, they were clockwork and would tick like a cartoon bomb.
  6. In South Australia, a little hydrogen is being added to natural gas at huge expense, but the amount can’t safely go above 5% without ripping out gas pipelines and replacing them, as well as replacing gas appliances.  I’d describe adding hydrogen to natural gas as putting pig on a lipstick, except that activity is a lot cheaper and some people enjoy it.
About Ronald Brakels

Joining SolarQuotes in 2015, Ronald has a knack for reading those tediously long documents put out by solar manufacturers and translating their contents into something consumers might find interesting. Master of heavily researched deep-dive blog posts, his relentless consumer advocacy has ruffled more than a few manufacturer's feathers over the years. Read Ronald's full bio.


  1. John Mitchell says

    An excellent article, but one thing Ron didn’t make clear is that the heating efficiency of a reverse cycle air conditioner or heat pump depends on transferring heat from the exterior. So the lower the external temperature, the harder the heat pump has to work and the less efficient it becomes. Below certain temperatures it just can’t raise the temperature enough. Still overall, reverse cycle air conditioning is going to be much more efficient, except in really cold climates where a ground source heat pump probably makes more sense. Only Tasmania really fits this profile in Australia.

    **Mistake in table for Sydney where gas is incorrectly labelled in kWh.

  2. David Morgan says

    The problem in our household is that the split system heat pump is much noisier and draftier that the ducted gas heating. And a ducted heat pump system is extremely expensive, particularly, I was told, because it could not use the existing ducts. Our gas heater died, and I decided to not replace it, and installed the heat pump. After a few weeks I was over-ruled and we bought a new gas unit.

    • Finn Peacock says

      What brand and model of heat pump did you buy? Who installed it?

      • David Morgan says

        6kW Toshiba RAS-22N3KV2-A/AV2- installed by C. B. Air – ABN 61 092 231 046
        It is not really noisy; just noisier than the ducted system. Enough to be distracting while watching TV.

  3. Jonathan Gaul says

    In Thredbo, NSW ELGAS (aka foreign-owned Linde/BOC) charges me
    at the rate of $0.050276/MJ for reticulated LPG – plus service charges.

    • Tim Forcey says

      Get an air con for heating.

      Modern air cons are rated to work down to even minus 20 deg C outside temp. OK for Thredbo Village even.

      • Jonathan Gaul says

        Thanks Tim, I’ll check out which makers reckon their heat pump works at
        such low temps as Thredbo – usually not lower than minus 10C


      • Randy WESTER says

        Look at a table of heat pump efficiency vs. temperature, and understand what the cost is going to be where you live.

        Yes, air source heat pumps do work at outside air temperatures of minus 20 C. But the Coefficient of Performance is going to be barely 1.5, so a typical Canadian system would be a hybrid of an electric air or ground source heat pump, plus a high efficiency gas furnace rated at about 95%.

        The highest efficiency Canadian homes can be heated with 1300 watts at minus 20, and cooled by adding ice to the drinks.

        I’m curious, the article seemed very either-or, no mention of woodburning stoves, wood pellet stokers, or other biomass. Are wood pellet heaters not used in Australia?

        • Geoff Miell says

          Randy WESTER,
          You state: “The highest efficiency Canadian homes can be heated with 1300 watts at minus 20…

          Apparently there are now quite a few “Passive” buildings in Canada.

          Passive houses are called that because they’re generally designed to stay at a comfortable temperature without “active” heating and cooling like furnaces and air conditioners.

          Per a Government of Canada website re Heating and Cooling With a Heat Pump:


          In Canada, where air temperatures can go below –30°C, ground-source systems are able to operate more efficiently because they take advantage of warmer and more stable ground temperatures. Typical water temperatures entering the ground-source heat pump are generally above 0°C, yielding a COP of around 3 for most systems during the coldest winter months.

          The simple message is: You don’t need to burn stuff to have useful heating (or cooling) in your home, even in Canada.

          • Randy WESTER says

            That’s perfectly true, it is quite possible to heat a home in Alberta, using a ground source heat pump, provided it’s a drilled well system, because the ground freezes to a depth of 8 feet here, especially if you start pumping heat out of it in late summer when it’s 5 degrees C in the morning.

            And you’re partly right, combustion inside the home is unnecessary. But combustion at a power plant is required, or there’s no electricity.

            Canada has a dramatically varied climate, and the majority of people live in areas served by massive hydro power stations. But Alberta is no more connected to Ontario and Quebec’s hydro than to Queensland and West Australia. . There’s a connection to BC Hydro, about 800 MW, but they get first dibs, and they get winter at the same time of year.

            The rest of the story is that up until recently, Alberta’s electricity was about 50 percent coal, 40 percent gas. The carbon emissions at a C.O.P. of 3 and 40 percent efficient coal power are much higher than from a 97 percent gas furnace. Don’t take my word for it, work out the KWh vs. Kg carbon yourself.

            Now, as of 2021 the electricity is going to be 85% natural gas, plus some imported mixed power., 5% hydro, sawdust, wind, and solar. The solar is insignificant in winter, wind is strongest spring and fall, and most river melt runoff is obviously in midsummer, too. So winter electricity is 90% from natural gas.

            Much of the natural gas electricity is from simple cycle turbine ‘peakers’ and gas fired steam. I’ll be generous and call it 35% efficient, then we’ll take off 10% for line loss. Multiply by a 3x Coefficient of Performance, and dangit!, still not up to the 97% efficiency of the gas furnace that’s already in my basement!

            The only ways to reduce household carbon emissions here arr to put in a large solar PV system, make the house airtight, and insulate well with at least triple pane windows. Those things work in hot climates, too, by the way, but perversely some may be subject to property tax, so you might not actually save much money.

  4. Geoff Miell says

    You state in your piece:

    No matter how old your reverse cycle air conditioner is, you’re likely to be financially better off using it for heat than gas. The only exception may be if you’re in Melbourne and your air conditioner is ancient and one of the least efficient ever sold.

    I wonder what Melbourne-based energy advisor Tim Forcey would have to say about that, Ronald? I’d suggest it would probably have to be a very decrepit and antiquated air con.

    Forcey is assuming gas is supplied to the home at a “fairly low price of $0.02/megajoule.” – a bit more than your indicated Melbourne price at $0.015/MJ.

    In a RenewEconomy article headlined “Households want gas?” Fossil fuel industry telling tales as it fights for its future by Tim Forcey, dated Aug 20, it includes:

    In our home, we now heat with air cons at a cost only 1/3rd of the now-decommissioned ducted gas. Our 2015 University of Melbourne research showed some households can save more than $1,000 each heating season, research that has now been proven in thousands of homes across Australia.

    Daikin Australia is apparently claiming:

    Save up to 63% on your heating running costs when you switch from gas heater to a Daikin split system in NSW.

    The message is simple: Switch from gas to all-electric.

    • Tim Forcey says

      Undoubtedly somewhere in Australia there is an air con that performs very poorly!

      Just as there are crazy inefficient gas heaters. I had a client with an old inefficient ducted gas heater mounted outside the house. If any bird had happened to fly through the scorching hot exhaust flue gases, it would have immediately burst into flames! Nearly…

      Check filters. That can be one reason a heater performs poorly. Filthy filters.

  5. Tim Forcey says


    When you try to burn gas/methane, some of the methane remains uncombusted.

    So the methane that missed being burned goes on to do its global warming thing even better than the CO2 it might have become.

    • Randy WESTER says

      Nearly all the unburned methane from a gas appliance is during ignition and at shutdown.

      So an oversized gas furnace will cycle on and off more often, depending on thermostat settings.

      And, a tankless hot water heater may cycle far more often than a tank type unit, so it may emit slightly less CO2 in a year, but 50 times more CH4.

      A combined cycle gas turbine powerplant is both more efficient and lower CH4 emissions than household gas appliances, because it doesn’t cycle on and off more than a few times a year.

      Our 10 yr old house in Alberta, Canada needs about 7,000 KWh of heat a month in the dead of winter, which would cost about $1300 as electricity, and $200 as natural gas. So airtightness and insulation are key first step toward electrification.

      Winter electricity in Alberta will be about 90% from natural gas in 2020, all the coal plants are converted or shut down, and the solar PV output in December is insignificant.

  6. Tim Forcey says


    A 34,000 member facebook group, heating with air cons.

  7. You have not counted electricity that a fan consumes, also can add losses on ducts if we talk about ducted systems.

    • Gas systems also have fans & ducts.

    • Randy WESTER says

      Unlike for cooling where heat given off by a motor is doing the opposite of what the system is trying to do, 100% of the electricity consumed by the fan motor in overcoming air friction in the ducts is turned into heat, so wouldn’t that be less of a concern?

  8. Brian C Ashworth says

    I’m surprised you didn’t include bottled gas in your analysis. . . . it makes mains gas seem cheap.

  9. Mark Stokes says

    So, outside of heat pumps, I figured it made minor economic sense to use a kettle on the gas stovetop instead of the electric kettle during hours of darkness when is solar not working. I now so enjoy the quieter operation when heating and the satisfying whistle when complete that I even use it when the solar is available and it doesn’t make economic sense!

    • Geoff Miell says

      Mark Stokes,
      In energy advisor Tim Forcey’s Explainer: How induction cooktops work – and clear the air, published Jun 2, it begins with (bold text my emphasis):

      If you aren’t burning gas in your home for space or water heating (see our previous Explainers 1 and 2), there might be one gas user left in your home: the cooktop.

      Though your cooktop will only burn a small volume of gas throughout the year, you might still be receiving a big gas bill largely for the privilege of remaining connected to the gas grid. Time to re-consider if you want to be “cooking with gas” and would rather be “cooking with induction”.

      Forcey also says about gas: “It’s flammable, potentially explosive, and produces toxic and even acutely fatal by-products when used.

      The message is simple: Switch from gas to all-electric – it’s cheaper, safer, and healthier.

      • Mark Stokes says

        That’s true about the gas connection fixed fee. I have heat pumps for heating and cooling but town gas for water heating and cook tops. I figure I should install electric hot water and put my surplus solar power into that. Then I might re-jet the cooktops to run off gas bottles and disconnect from the town gas so I don’t have to buy new cooktops (I have two, one of which is part of a big oven)

  10. Michael Ouellette says

    The comparison is Daiken split system vs a Gas space heater, not ducted. I’m not sure if the savings would be that dramatic with a ducted system.

  11. Adam Creed says

    I live in Melbourne and have gas ducted heating and have been considering replacing with a split system (I have solar also). But I am hesitant by reports you cant use the existing ducts. My house is small with 3 bedrooms along a hallway and I don’t really want to put in a split system in each room! But perhaps you can use the ducts, and perhaps one split system would be enough to heat the small house, despite all the brick walls and hallway. I am really unsure.

    • Tim Chirgwin says

      We use a wood heater, even though we have a reverse cycle aircon ( used very few times as heater),… we cut our own wood so energy is extra cheap and less draughty than reverse cycle heating,….but.
      I use the inbuilt fan to pull heat off the wood stove surface , which makes a significant difference to efficiency (less wood burnt)…and also run a small pedestal fan to circulate the air around the room and pull extra heat away from the chimney,… this makes a massive difference to the whole house heat effectiveness instead of most heat going through the insulation immediately next to the chimney outlet where the ceiling can easily be 60deg C.
      This ceiling heat is from rising air straight up off the stove,..the flue is properly shielded and safe. Not only does this pedestal fan make the adjoining room warmer but also down the hallway to all bedrooms.
      I would suggest that keeping the warmth within the building envelope (rather than ducted transfer where heating and cooling effort is lost through the roof cavity), is much more energy efficient and also much cheaper than fitting ducted anything, this would apply no matter what energy source you use.
      Perhaps some energy efficiency expert may comment,…I’ve only got experience.
      Cheers Tim.

      • Adam Creed says

        Yes, it makes sense that I would lose some efficiency through the ducts, and I am already in this situation with ducted gas heating. I would quite like to go ductless but not sure how that would work with my house layout, unless one split system is enough for the whole house.

    • David Morgan says

      The story that I was given, and I am happy to be corrected, is that a ducted heat pump “heater” will also be a ducted cooler, and that the existing ducts are not well enough insulated to carry cold air without getting condensation on the outside. The corollory would seem to be that the ducts are a significant source of heat loss, decreasing heating efficiency. Not all the heat coming out of the heater gets to the room.

  12. Ian Thompson says

    Hi Ronald

    I’d like to query your assumption that here in Australia our coal-fired stations produce only about 1 kg of CO2 per 1 kWh of electrical energy produced.

    This site suggests (roll down to the bottom of the page), that Hard Coal can on average produce only 1 kg CO2 / kWh generated – in Germany which has Supercritical plants, and Ultra-Supercritical plants – but here in Australia we only appear to have decrepit old sub-critical plants so would be considered at the lower end of the efficiency scale – and also generally use lower quality coal (e.g. Brown Coal in Victoria). I’d think our coal stations would mostly battle to achieve 35% nett thermal efficiency. Looking at the chart, this would suggest we might be producing in the order of 20-30% more CO2 – therefore closer to 1.25 kg CO2 / kWh of electricity GENERATED.
    But, of course energy at the power station is not the same as energy at the household – typically around 15% will be lost in transformers, transmission lines, distribution lines, etc., leaving only 85% to be used in your reverse cycle air-conditioner. i.e. 1.25 / 0.85 = 1.47 kg CO2 / kWh of energy actually CONSUMED.

    We have both NG & Grid power & Solar connected, but here in Perth solve the problem by using NONE of the above sources for home heating (nor wood) – the NG was connected when we purchased our home many, many years ago – but we only use it for barbecues and an historical gas oven.

    Quite simply, when it is cold (for Perth) we simply wear an extra jacket, or an old dressing gown when at home at night. Zero (0) extra CO2…

    In summer, we only very, very occasionally use A/C for cooling – then mostly from Solar PV…

    Like driving a car – I think major savings in efficiency and emissions reductions can be made according to personal behaviour.

    • Ronald Brakels says

      When emission from extraction and approximately 7% transmission losses are accounted for, I am certain Australian coal emits over 1kg of CO2 per kilowatt-hour of generation consumed on average. But I used a nice round figure of 1kg per kilowatt-hour because even with this low ball figure the emission benefits of using heat pumps for heating over gas are very clear.

  13. Good article, Ronald, thanks. Perhaps more could have been said about capital costs, as opposed to running costs.

    In colder areas, such as in the Blue Mountains west of Sydney, the size of heater required means that installation of additional electric capacity into the household is usually necessary if an electric reverse cycle conditioner is to be installed.

    This requirement is exacerbated by the fact that the external temperature is often close to 0 deg C in winter. At such times, the coefficient of performance of even a modern electric heater is about 1.3, which is well below the efficiency figures you have generally indicated. The heater then has to be large enough to cope with such times when it is most needed. Its kWh rating will therefore be similar to that of an equivalent gas heater, not approx 3.5 times less as implied in your article. Further, any air-source electric heater must be of the more expensive type that is able to cycle onto inefficient resistance heating to prevent the external condenser coils from freezing when the external temperature drops below about 4 deg C. (A ground-source electric heater is an alternative, but these are even more expensive to install.)

    Thus in colder areas, capital costs for electric heating are often much higher than for equivalent gas heating.

    • Geoff Miell says

      Ken Crane,
      You state: “At such times, the coefficient of performance of even a modern electric heater is about 1.3, which is well below the efficiency figures you have generally indicated.

      Where do you get the figure “1.3” from, Ken?

      It seems for a range of output temperatures (i.e. +67 °C, +59 °C, +51 °C, +43 °C, & +35 °C) air-sourced heat pumps with R32 refrigerant for space heating indicate that the CoPs are significantly above 2.0 at 0 °C ambient input air temperature – see:

      I have a 5.0 kW (cooling) / 6.0 kW (heating) capacity split-system reverse-cycle air conditioner with R32 refrigerant that I use for both heating and cooling at Lithgow that serves two rooms. Lithgow minimum ambient temperatures can get down to -8 °C – still well above the air con’s -15 °C minimum operating limit.

      I had a flued gas space heater before I installed the air con in 2017. The air con is certainly much cheaper for heating than the gas heater. And I can pre-heat the rooms during the day using energy from the solar-PV panels for more savings.

      I also have an air-sourced heat pump hot water system (with R744 refrigerant) with a 250 litre storage tank that’s programmed to operate from 10am to utilize energy from the solar-PV system.

      In my experience, air-sourced heat pumps work satisfactorily in Lithgow, so they will likely work just as well in the Blue Mountains.

  14. Malcolm Hazell says

    I”ve recently installed a 13.5 KwH solar system in Canberra (36 Trina panels; Fronius inverter, no battery) and this all happened through your solarquotes system which I am extremely happy with – thanks. Currently we use a US-made Lennox ducted gas heating system with a Lennox airconditioner/cooler for the summer. The unit is around 15 years old so I can’t expect it to last a lot longer despite being well maintained. One of the reasons we used this gas heating system was because we have a valuable piano and artworks and we found that our original electric heaters dried us out, and also our piano and artworks. The Lennox system has a humidifier attached to it which can be set to suit the outside temperature – and this has proved beneficial in Canberra’s dry heat especially. I was really interested to read your latest article on the pros and cons of reverse cycle heaters over gas and would greatly appreciate any comments you have taking into account my factors above. Are there reverse cycle systems (heating and cooling) which won’t dry us out and importantly are gentle on pianos too? One of the reasons I installed a large PV system was to cope with potentially increased electricity usage if I can’t/shouldn’t replace the current gas heating. Would appreciate your comments/suggestions please.

    • Ronald Brakels says

      There are “precision” air conditioners that can accurately control humidity land temperature evels that are used for locations with sensitive artworks or electronic equipment. Unfortunately, I don’t know how much these may set you back or which brands are the best. But I doubt you’ll need the sort that are used by art galleries or server rooms.

      I suggest looking for an air conditioner that gives good control over humidity levels and setting it at a level you find comfortable.

  15. Adam Watts says

    I’m not sure how you came up with the price of gas for Perth. I only pay 2.6c per MJ, there are some plans available that are even less.

    • Ronald Brakels says

      That was the cheapest one I found from AGL. If you let me know the name of your plan I’ll update the article.

      • Adam Watts says

        I am on the Kleenheat monthly smart saver plus additional 3% discount for RAC membership. Paying 9.52c per unit (1 unit in WA is 3.6MJ) so 9.52 divided by 3.6 equals 2.6c per MJ.
        Other costs are 22.23c per day supply charge and account fees of about $5 per quarter.

        • Ronald Brakels says

          Thank you very much for that. I see my mistake was thinking a unit of gas in WA was a megajoule as it is in other states, instead of a kilowatt-hour. I have corrected the article to reflect the lower gas price.

  16. With a recent Hydronic installation, our supplier advised that heat pumps would need to be huge to enable water temps to get to the correct range in Mornington Peninsula . So we are on gas. We chose hydronic to avoid the dryness of blowing ducted air around the house. What are you opinions on how to supply hot water for radiators using electric heat pumps. Can this realistically work and how can it be retrofitted. BTW Vic government rumours say that gas will be unavailable after 2025! Any information on that?

    • Geoff Miell says


      Forcey stresses that gas is no longer necessary to heat your home and water or to cook food, as the cost of heat pumps and induction cooktops comes down. “Australians are wasting billions of dollars every year burning gas in their homes. Now there are cheaper options,” he said.

      See also Tim Forcey’s comment at:

      Bruce Robertson (gas analyst at IEEFA) says at time interval 0:01:22 in the video below):
      There’s so much gas in Australia. We are swimming in gas.

      • Ian Thompson says

        Hi Geoffrey Miell

        I’m finding the grammar in your Forcey quote to Alistair a little ambiguous/confusing.

        Putting CO2 emissions to one side, for the moment, is he saying the price of heat pumps and induction cooktops HAS come down sufficiently to make their use more financially beneficial than continuing to use existing NG equipment, or is he saying (“as the cost…comes down”) they WILL become financially beneficial in the future (but perhaps not just yet)?

        My experience is that heat pumps remain quite expensive (in capital cost terms) at the moment, and are relatively short-lived – making them difficult to justify if you already have a serviceable NG water heater (I don’t).
        To put this into perspective, a friend of mine just replaced his Solar (thermal) HWS for around $4,000 – he reports this very seldom required boosting, and was 34 years old – as well, it was still working perfectly, and the only reason for changing was that the box enclosing the panels was falling apart. His tank was stainless steel – but this brand has ceased production here in Perth, or elsewhere as far as I know. Such a pity, as the performance of the replacement appears considerably inferior, as is the likely lifespan and ongoing maintenance costs.

        I have a functional Ceramic electric cooktop, and am finding it hard to justify replacing it (and ALL of our pots and pans) with an induction cooktop. Especially when efficiency only changes from about 74%, to 85% (depending what site you look at). Changing our old gas oven to electric would also involve MAJOR costs – as when we got rooftop PV, the meter box was totally packed – so as well as the cost of the oven, we would have to also pay for substantial re-wiring, and have our meter box totally replaced with a larger one and re-wired (includes brick-work, new box, new panel, new breakers, etc.) – as Alex points out below. Saving the NG connection fee (our gas use is very, very modest), doesn’t come near covering our major costs otherwise.

        Yes – I 100% agree (from a GHG perspective) that NG has to go away for new housing developments – and for everything else in time – but I feel even these will all be disadvantaged by the additional costs.

        There is a difference between REPLACING existing functional equipment, and INSTALLING new, or replacing old equipment that has failed.

        • Geoff Miell says

          Ian Thompson,
          I think the quoted statements by Tim Forcey are crystal clear and unambiguous: “Australians are wasting billions of dollars every year burning gas in their homes. Now there are cheaper options.

          Re your arguments about the costs of transitioning to all-electric appliances in your home, I wish draw your (and anyone else’s) attention to the op-ed by climate scientists James Dyke, Robert Watson and Wolfgang Knorr, in The Conversation on Apr 22, that included (bold text my emphasis):

          We have arrived at the painful realisation that the idea of net zero has licensed a recklessly cavalier ‘burn now, pay later’ approach which has seen carbon emissions continue to soar…

          The time has come to voice our fears and be honest with wider society. Current net zero policies will not keep warming to within 1.5°C because they were never intended to. They were and still are driven by a need to protect business as usual, not the climate. If we want to keep people safe then large and sustained cuts to carbon emissions need to happen now.

          And who will pay for our/humanity’s cavalier behaviour?

          Dr James Hansen, Director of Climate Science, Awareness and Solutions at Columbia University, together with Dr Makiko Sato, Senior Staff Associate at Columbia University, posted their July Temperature Update: Faustian Payment Comes Due on Aug 13, and it concludes with (bold text my emphasis):

          The Faustian payment that we noted in 1990[7] and is discussed in detail elsewhere[8] is now due. Dr. Faust had to pay the debt himself. We have willed it to our children and grandchildren.

          And I’d suggest if you think you may still be ‘vertical’ in the 2030s, when the Earth System has likely risen above the +1.5 °C global mean warming threshold (relative to Holocene Epoch pre-industrial age), you too may well be paying the price of a ‘burn now, pay later’ approach.

          Risks of simultaneous crop failure, however, do increase disproportionately between 1.5 and 2 °C, so surpassing the 1.5 °C threshold will represent a threat to global food security.

          • Ian Thompson says

            Geoffrey Miell

            Sorry not to instantly fall into lock-step with your mantras – but you don’t appear to have thought your comments through…!

            Tim Forcey’s “crystal clear and unambiguous” observation cannot be generalised, as you have; as the situation is quite clearly ‘horses-for-courses’ when it comes to ‘wasting billions of dollars each year’. In my own particular case, yes we could change out our old gas oven for electric – but the costs (in our individual situation) would prove horrendous, and we would NEVER, EVER recover the extra costs within our remaining lifetime. So, your ‘generalised’ mantra is proven false by exception. Tim probably means “Some Australians…are wasting billions…”.

            IMHO, the issue IS NOT cost, but rather a desire to reduce/eliminate GHG’s. Some will save money changing away from gas, some will not. You appear to have been blind-sided by your ideology.

            Putting the (rubbish) cost argument aside, let’s think this issue through.

            Let’s say I do change away from gas, and start using more electricity instead. I have looked over numerous websites, and many say gas ovens heat up quicker than electric, and use little gas when running – but some say electric heats quicker. Some say the electric oven runs at it’s rated 2.4kW, but this is patently rubbish (except during warm-up), as both gas, and electric ovens are modulated by their thermostats. I could not find anything to say electric is more efficient (energy-wise), sometimes quite the contrary, so the jury is out – I’m going to assume their ENERGY use is somewhat similar. So, instead of consuming 1 kWh of gas (or MJ equivalent) directly in our old gas oven, we now draw 1 kWh of electricity from the grid to do the same job.

            But Geoffrey – were is that (extra) electricity going to come from – now, during Transition? I could say from my rooftop PV, but we usually cook dinner after sundown – and anyway even if we cooked earlier this would simply mean less exports to save GHG’s elsewhere – and my following observations will still apply. The reality is, at present, during transition, that either a coal or NG station will have to run just that little bit harder to provide my extra electric power. And, it’s thermal efficiency is probably around 35%, so it will have to burn 1 kWh divided by 35% = 1 / 0.35 = 2.86 kWh extra NG to make the 1 kWh of energy I need to replace. Then, the transmission to my home might be only 85% efficient – but let’s be generous and say 90% efficient. So, the power station will have to put in somewhat more than 2.86 kWh into the grid, for me to recover the 1 kWh we require. In fact, 2.86 / 90% = 3.2 kWh of thermal energy.

            Say what, Geoffrey? – you want me to emit 320% as much GHG’s (or more) by buying an electric oven, than what I am doing presently? As well, you want me to contribute more to landfill, and expend more energy to manufacture this flash electric oven replacement? Now who is being the more responsible?

            Of course, I AM assuming there is no ‘spare’ renewable energy just ‘floating around’ – being curtailed – ready to pick up the slack for my added needs. If there is, WHY? WHY is it not already being utilised? Are there unresolved technical problems? Prove to me that my extra demand, CAN be met from curtailed renewables!

            As I write this, WA is generating barely any solar, and precious little Wind energy – so I’d think my assumption is pretty reliable – renewables WOULD NOT be able to provide the extra 1 kWH needed. SA is running 1.36GW of NG, and I’d think Wind is probably flat out at 0.54GW (with no curtailment), with zero solar.
            If in fact some of the power has to come from coal, there will be increased CO2 emissions, if not GHG equivalence (due to fugitive emissions).

            So, Geoffrey – UNTIL we have fully renewable generation capacity to meet demand, I’d think the more responsible, and also lower cost option, for me AND the environment, is to stay with gas. And, I’d think, for a lot of other people. Of course, once we have technically competent fully renewable capacity, the situation changes – and I agree with that.

            Maybe there is another agenda here?

          • Geoff Miell says

            Ian Thompson,
            If for whatever reason, you don’t expect to remain living in your current home beyond the 2020s, then I’d expect you probably wouldn’t recover the costs of replacing your “old gas oven for electric.”

            What I think you haven’t grasped is that as more current gas customers discover that it is significantly cheaper to switch away from gas, particularly for space heating and hot water, and they do switch, then any remaining gas consumers who can’t or don’t yet choose all-electric appliances are at risk of future bill increases because less homes and businesses would share the cost of maintaining gas network services.

            As more gas customer defections increase and gas demand decreases, the exodus will likely grow into a so-called ‘death spiral’. I’d suggest alternatives like biogas and hydrogen are unlikely to be cost competitive to assist the gas distribution grid remaining viable, and thus the gas network faces becoming a ‘stranded asset’, perhaps in as little as 15 years, maybe even sooner.

            When questioned by the Queen in 2008 as to why the credit crisis had occurred, the British Academy, after much introspection, responded that a “psychology of denial” led to “a failure of the collective imagination of many bright people, both in this country and internationally, to understand the risks to the system as a whole.

            I think you, Ian, and others like you, are engaging in a ‘failure of imagination’ and ‘psychology of denial’ on the possibilities for the speed and scale of the energy transition.

          • Ian Thompson says

            Wow! Geoffrey Miell

            So you ARE advocating we very moderate users of gas, should TRIPLE (albeit somewhat temporarily) our present contribution to GHG from this source – until Renewables reach the point that they can (without fossil fuel back-up and considerable contribution), provide our energy demands. What has the ‘psychology of denial’ got to do with me wanting to reduce my GHG footprint?

            Sorry, it’s the 2020s NOW Geoffrey – and I don’t see renewables achieving that status any-time soon. Yes, I had anticipated your ‘death spiral’ agenda – but you need to understand that even if domestic use is terminated, then until we have adequate and technically competent renewable sources of energy to replace that loss, your agenda will ONLY result in more coal and NG consumption at power stations (with perhaps 3 times the GHG contributions as a result).

            Your ‘electricity is cheaper than gas’ statement is at present both misleading and unrepresentative in many cases. A lesson in economics, Geoffrey – someone who pre-pays $5,000 (with the Government stumping up a near equivalent $5,000) for a solar system, then gets bills for $0, can hardly claim his energy costs are zero. By extension, the fact that my monthly gas bill might be a little more expensive than an electrical equivalent energy amount, in no way means it is cheaper for me to change over to electric. The lesson – you also need to factor in the costs of Capital amortisation.

            Just so you know Geoffrey – WHEN we get to near 100% renewable sourced electricity, and won’t then have to rely on extra coal and/or NG consumption, I probably WILL buy a new electric oven – if I am still living – or even earlier if the gas oven decides to pack up irretrievably – or when and if gas prices go through the roof.
            For my part, I do have rooftop PV, reverse cycle A/C, and a rooftop solar (thermal) HWS. We DO NOT use 40kW of room heating, or cooling capacity in our home – our total energy for both approaches 0 (zero), year round. We try to use PV for boosting the HWS, only when we have to and can (and plan our use about this).

            I’m doing my bit – why don’t you…

          • Geoff Miell says

            Ian Thompson (Re your comment at August 30, 2021 at 6:58 pm),
            You state: “ Sorry, it’s the 2020s NOW Geoffrey – and I don’t see renewables achieving that status any-time soon.

            As of 1 Sep 2021, there are 8 years, and 4 months (or 3044 days) until the beginning of the 2030s. I’d suggest that much can happen in that time IF we/humanity have the will to do so – see:

            Please don’t lecture me on amortisation of a PV system – ICYMI, see:

            You state: I’m doing my bit

            IMO, indeed you sure are, Ian – downplaying/denigrating the energy transition, and promoting more gas use that is ‘dirtier’ than coal due to ‘fugitive emissions’/methane leaks that aren’t being officially accounted for. I’d suggest your GHG emissions footprint is far worse than you indicate with your ongoing gas use. But, hey – what you don’t see or wilfully ignore, is very convenient for easing consciences, eh Ian?

            I think you are one of these so-called ‘inactivists’ that Michael E Mann refers to:

            But the “inactivists”, as I call them, haven’t given up; they have simply shifted from hard denial to a new array of tactics that I describe in the book as the new climate war.

            I recognise the same classic ‘inactivist’ tactics here at this blog in multiple comments from you (that Mann describes): Denial; Deflection; and Division.

            You state: “… the fact that my monthly gas bill might be a little more expensive than an electrical equivalent energy amount, in no way means it is cheaper for me to change over to electric.

            That may be so NOW, but you are ignoring (there’s your apparent ‘failure of imagination’ again) what may likely happen to gas prices and supplies in the not-too-distant future.

            SA Senator Rex Patrick tweeted Aug 31 (including a 1:57 duration video):

            How can we be the largest gas exporter in the world, yet require gas import terminals? How can we have a domestic gas market that is getting smaller in size, yet the price of gas is going up? The answer is simple – cartels, monopolies and TOTAL POLICY FAILURE.


          • Ian Thompson says

            Sorry Geoffrey – I feel your philosophy/agenda/motives lack integrity, are bordering on EXTORTION, and some are patently stupid. I have to assume you lack technical competence to understand the simplest of calculations (and, you HAVE demonstrated this previously).

            No, Geoffrey, I AM NOT suggesting we burn MORE NG – never have. What I am suggesting is that we do not burn TRIPLE the amount of NG (or Coal) generated, in place of the lesser amount a small cohort uses presently. I can appreciate, if we go your way, in about 5-10 years you will be able to run around flapping yours hands in the air (Chicken Little style) saying “Look, Look – atmospheric methane form fugitive sources are still increasing – woe is us – pay out, pay out”.

            Again, you confuse the present, and the future. I AM NOT suggesting I will continue to burn gas if the price skyrockets, NOR have I suggested I’d keep burning gas once renewable sources become technically competent. I AM ONLY suggesting that in my case replacing my gas oven, with an electric oven, at the present time (NOT in the future), will result in:

            1. TRIPLE the GHG contributions I make from that source, and
            2. Prove VERY COSTLY to me – and I guess to many others.

            Again, sorry if you thought I was ‘lecturing’ you about amortisation – it’s not all about you – you often make statements about renewable cost comparisons that are quite simply false – so wanted to address this imbalance to more than just you. I was giving you the benefit of the doubt – many of your statements did appear to show you lacked financial understanding. Perhaps just deception, instead?

            Why don’t you focus on making renewable sources cost-effective and adequate for demand – the only State that does not appear to need fossil fuels at present, is Tasmania – although even they generate from some NG from time-to-time (I guess for grid stabilisation). Rather than extorting the public into forking out more and more for new renewable power station replacements – in a deceptive manner – which appears to be your ploy.

  17. One challenge for some homes hoping to make the switch from gas to electric for heating, hot water and/or cooking is their electricity supply may not be set up to handle the addition of such high power draw appliances.

    It can mean a significant and costly upgrade to their electricity connection and changes or replacement of their main circuit board are required.

    It’s a common issue with housing developments built down to a price – the minimum electrical connection was installed and it was assumed gas was supplying much of the home’s energy.

  18. Welcome everyone. I initiated this discussion.

    Thank you for your variety of comments.
    We have gone off on a philosophical tangent. I am seeking “practical” advice as per an HVAC engineer or similar.
    As mentioned I have a gas powered boiler supplying a Hydronic heating system. I DO NOT want ducted air I prefer the heated water radiators for health reasons amongst others .
    This unit supplies up to 40 Kw of energy heating water to up to 80 degrees. I discussed with my supplier the “heat pump” option and the response as detailed below basically says that after 12 Kw it’s not feasible . Please read the link below.

    Please can anyone shed further light on what options I have in future if I choose to move from gas and/or gas supply ceases or becomes unsustainably expensive.

    May I reinforce that I am seeking “practical” workable solutions not a philosophical thesis. Brgds

    • Geoff Miell says

      Wow, why do you need 40 kW of heating capacity for your home? Do you really need to use all of that capacity? Per the link you provide:

      In Australia, we have large homes that on average require 20kWs of heat energy. A 20kW heat pump is a very very large heat pump with a price to match.

      It seems to me, based on your indicated heat requirement, you have an enormous home, or you have a very thermally inefficient home, or both.

      I’d suggest perhaps instead you need to consider improving the thermal efficiency of the envelope of your home. Try eliminating all drafts from building envelope air leaks (i.e. doors, windows, vents, etc.), improve the building envelope insulation where possible, and perhaps consider replacing single glazing with high performance double glazing with thermally-broken frames (at least in the living areas). These are one-off costs – not recurring operating costs.

      You state: “…after 12 Kw it’s not feasible.

      A quick web search indicates the data sheet for Stiebel Eltron models WPL 25 AC (3-phase) & WPL 25 ACS (1-phase) both offer 14 kW of heat output. There’s also a commercial unit model WPL 57 (3-phase only) offering 31 kW of heat output. Anything (within the constraints of the Laws of Physics) is possible for a price.

      There may be other comparable brands/models, but do you really need 40 kW of heat, Alistair?

      I’d suggest you need to discuss your very particular situation & needs with an appropriate and competent professional energy advisor to get the best practical advice.

  19. Gooday Geoff,

    Thanks for your input which I will pursue.

    This is new build, we moved in 2 months ago. The house ( as per all new builds in Vic) exceeded the 6 star energy rating and we have all windows thermally broken DBL glazed. Insulation underfloor of R4 and all external walls R6 and internal walls R3 and in ceiling R8 plus the thermal blanket, under Colourbond roof. The home is built from masonry. We are rated N2 for wind as we overlook Port Phillip Bay and can have winds in excess of 130 kph.
    So Yep our consultant at DPP calculated our needs and with 13 panel radiators and two towel rails in a 20 square house that’s what we need. 40 Kw!

    So where’s the professional energy advisor (perhaps Finn) who can help me plan , in due course to move to a heat pump, when the Vic government ceases gas supply in 2025? Of course I did have this conversation with my hydronic supplier prior to signing the contract as we preferred to NOT use gas, but as you’ve seen from the information I posted we would never be able to achieve sufficient Kw to make it work!


    • Ronald Brakels says

      Gas connections may not be permitted for new residential developments in the near future in Victoria, but there are no plans to cut off gas for existing users I know of.

      The maximum amount of heating I have ever used in Australia is about 3 kilowatts. Possibly 5 if someone had an electrical resistance heater on at the same time as the air conditioner. That 40 kilowatts of heating figure makes me think the hydronics system must be losing a lot of heat to the ground. If these systems don’t follow European style standards of installation, a lot of heat can be lost to the building’s foundations and then to ground water.

      The good news is, provided a heat pump is efficient, it should draw less than 10 kilowatts of electricity — although that’s still a lot.

      UPDATE: But using gas will result in higher operating costs than a reasonably efficient heat pump.

    • Geoff Miell says

      From a Renew article published 3 Jul 2018, headlined Heating case study: converting gas to heat pump hydronic, it includes:

      In a project completed in November 2017, the owners replaced the gas boiler on their existing hydronic heating system with an electric heat pump, while retaining the original 25-year-old radiators.

      Owner Peter Hormann says they did a lot of work to check whether a heat pump system would enable the 25-year-old radiators to deliver sufficient heat for their winter heating requirements. An important consideration is the lower operating temperatures of a heat pump system which is most efficient up to 55 °C (though can run up to 60 °C or 65 °C) compared to 70 °C from a gas hydronic boiler.

      While working out their upgrade options, they limited their old gas boiler to 55 °C through two Melbourne winters to test the existing radiator effectiveness at lower system operating temperatures. “We found that with the lower radiator temperatures the room heating was more gradual and took an extra 30 minutes to bring the house up from a 17 °C standby temperature to our 21 °C ‘comfort’ temperature,” says Peter. To compensate, their household thermostat was programmed for an earlier start in the morning and late afternoon heating periods.

      I’d suggest you may wish to try doing similar experimenting with your current gas hydronic heating system and observe what the results will be, before committing to switching to a heat pump?

      The case study given in the link suggests to me it’s possible to replace a 40 kW gas boiler with a 14 kW output heat pump with a buffer storage tank, albeit with a slower ramp heating response.

      If at all possible, try improving the thermal insulation of the piping network between the gas boiler and radiators.

  20. Thank you Ronald,

    Now I’m really Bamboozzled!!

    I was quoted a 40 kw Hydronic boiler but checking the installation it appears I have been supplied a 30Kw Bosch Condens 5000W unit. ZSB-302A.

    Nevertheless you are saying the maximum amount of Kw in Australia is 3-5 Kw, now that’s really compromised my mind!

    Given I have in room radiators how does a system “lose a lot of heat to the ground” and “heat to the buildings foundations and then to ground water” . Please explain; I am seeking a solution but becoming very confused as my Hydonic supplier has confirmed the boiler unit I have is the MOST popular choice in Victoria so I’m not alone!! Very happy to have a chat “offline” over the phone as I’m feeling I need to resolve this issue and I’m going down several non terminating rabbit holes. Brgds

    • Ronald Brakels says

      Okay, now I see what you have — a 30Kw Bosch Condens 5000W unit. ZSB-302A — I don’t know why you were told 40 kilowatts, but this unit will put out about 30 kilowatts of continuous heat. It’s apparently 90% efficient, which is very good for a gas appliance. Also, it shouldn’t heat your foundation more than other conventional heating. If you instead had an efficient heat pump supplying heat instead of this gas boiler your operating costs should be considerably lower. How much lower will depend on just what you pay for gas and electricity and what your solar output and feed-in tariff is like.

      I mentioned the 5 kilowatt figure for my heating just so you would know that I’m no expert when it comes to providing houses with large amounts of heat.

  21. Thanks again Geoff, appreciate your thoughts . The system uses Pex-al-pex piping with 60mm rubber lagging throughout so I guess that’s reasonable.

    I may have neglected to mention in its current configuration (ie gas) its fabulous. Never been warmer great performance. Brilliant to operate and very modest bills using the Google NEST thermostat.

    Thanks again for your input. In due course when I’m ready to change to a heat pump I know where to go. Brgds

  22. Adam Stanley says

    Hi, Ronald. Just a quick note to say THANK YOU for the clear and unbiased discussion on Gas Heating. Great info and much appreciated. Is there any good info on what brands are the most reliable overall? Every HVAC company seems to push whatever brand they typically carry or are familiar with. I’ve been using a Lenox system for many years and considering changing it. Any suggestion for that?

  23. Tony Mugan says

    Have you conisdered updating this article with the current environment of prices for electricity and gas? 2022 changed a lot of things.

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