Overcoming A Skinny Grid Connection: How To Get More Amps To Your House

Australians eager to fully electrify their home often hit an unexpected snag: the size of the copper cable from the grid to the house. This small but crucial detail can stall your electrification ambitions.

Here are some options for overcoming a skinny grid connection.

The Electrical Limitations Of Modern Homes

These days, an ordinary Aussie house in the suburbs has a 63 amp nominal supply, in either single or 3 phase, usually delivered from a 16 mm² cable.

Some homes only have a 40 amp supply, which is usually acceptable for a 3-phase system delivering 120 amps in total.

Older homes, though, might only have 32 amps, a vestige of the past, and will struggle to meet the demands of modern, all-electric living.

In more rural settings, where electricity may come from a single-wire earth return (SWER) transformer, a 5 kVa/20 amp supply was once standard. This setup was enough for essential services like night-time hot water and daytime cooking, plus the simpler needs of lighting and a radio.

What About New Builds?

Project builders, aiming to cut costs, frequently opt for the bare minimum in electrical infrastructure. This practice corners new homeowners, limiting appliance upgrades and solar adoption—a short-term saving at the cost of long-term flexibility. Where possible, talk to your builder about beefing up your electrical supply (including a bigger switchboard) before the build starts.

Gas Needs To Go

Many new homes get by with weak electrical setups because much of their power needs, like heating and hot water, come from gas pipes, not wires. But now, with behind-the-meter solar in Australia being so cheap, lots of us want to ditch gas. We’ve just got to figure out how to do it with our existing grid connections.

First, Test The Existing Wiring

There are steps any electrician can take to help. As a trade, they’ll be cautious when calculating maximum demand on a building plan.

If your place was planned on paper with a 32 amp supply, get an electrician to plug in four 1.8kW kettles and measure what’s available. Eliminating assumptions, and testing the wiring might prove you already have enough copper to run up to 40 amps. You’ll never know until you test it.

Upgrade To 3-Phase Where Affordable

If you’re lucky, and the conduit out to the street is straight enough to pull new wires, or the overhead supply is easy to replace, then upgrading to a 3-phase power supply can be a great way to triple your available energy.

Next, Look At Batteries

A quick water analogy is in order.

Most houses have an incoming water pipe about the size of your thumb. While you might use 300 litres per day, there’s potential for perhaps 2,000 litres per hour if you leave all the taps open.

If that water supply pipe was cut down to the size of a pencil, you could still get 300 litres of water per day, but would you be happy having a shower under something akin to the windscreen washer on your car?

What’s needed is some storage on your side of the water meter. Put a tank on the roof that is filled gradually through the skinny pipe, then plumb your shower with your own fat pipe.

Home batteries provide the same service for your electric power, letting you use more power than your grid connection can deliver.

Selectronic grid hybrid

Even with only 20amps available from the grid, a 5kW Selectronic can give you an additional 52amp surge capacity without overloading the thin connection.

How Many Solar Panels?

If you get a battery to buffer your power demand, you’d be nuts not to pair it with solar panels.

How many? For 15 years, my repeated mantra has been this: nobody has ever complained that they installed too much solar.

Even those in the solar industry need to get their heads around the idea that limited-size solar systems are not an efficient use of money. They are a waste of sunshine.

Export limits and curtailment might be annoying, but excess solar generation is a feature, not a bug.

It’s about the principles used when designing an off-grid power system. If you install enough solar to meet demand in the winter — when the sun is scarce, and heating needs are high — then in the summer, you’ll be swimming in it. Literally, if you have a heat-pump heated pool.

Your EV Charger May Require Load Balancing

EV chargers pull a lot of current but are still feasible for those with skinny grid connections, thanks to load balancing. If you have a 7 kW, single-phase EV charger, it will use all the amps available on a 32 amp supply (32 amps x 230 V = 7.36 kW). However, load-balancing smarts are available in some EV charger models, so your car charger can throttle itself when other demands are on the system, effectively sharing the available power.

Keep Connected To The Grid

Don’t be tempted to throw in the towel and go off the grid. Mains electricity is a first-world blessing, a genuine public good that we should cherish and be willing to share. It’s not wise to go entirely off-grid in the suburbs because grid supply will be cheaper and quieter than the generator you’ll otherwise need.

However, I’ve seen quotes for upgrading a skinny grid connection ranging from $60 to $600,000.

In most cases, using a solar + battery is much cheaper than paying that money to the local electricity network. You can significantly augment your supply with 10 kW single-phase hybrid inverters from Fronius or Sungrow. Or, like me, you can do the job properly with a Selectronic SPPro.

About Anthony Bennett

Anthony joined the SolarQuotes team in 2022. He’s a licensed electrician, builder, roofer and solar installer who for 14 years did jobs all over SA - residential, commercial, on-grid and off-grid. A true enthusiast with a skillset the typical solar installer might not have, his blogs are typically deep dives that draw on his decades of experience in the industry to educate and entertain. Read Anthony's full bio.

Comments

  1. Hi Anthony-Would value your comments on this: Almost everyone says “flood your roof with solar panels”, without taking into account that some of us will never get an EV , or a swimming pool, or a spa or a lear jet to keep charged on the backyard runway. Had a solar bloke who I trust come out to assess my system (1.5kw 15 years old currently on 66c fit). He looked at my 15 years useage and said that no, keep your existing system as it is quite sufficient for your needs even in winter. ???

    • Anthony Bennett says

      Hi Vaughn,

      66c FIT is the kind of gearing that means 1.5kW is still viable. I struggle to believe anyone has a consumption profile so low that 1.5kW will make much sense without the old tariff but that’s not to say it’s impossible.

      I’ve seen analysis which explains diminishing returns on 15kW systems compared to 6.6kW for a modest user but I still maintain that nobody has ever complained to me that they installed too much PV on the roof.

      We’ll look into it soon no doubt but the bottom line going forward is going to be sizing solar for winter. Excess solar yield is a feature, not a bug.

      Cheers

  2. Too late for me when I installed my swim spa a few years ago with several recirculation pumps and 2 wave pumps. I was told new download and meter box or no spa

    • Anthony Bennett says

      Hi Clive,

      Inverters and batteries are getting better & cheaper but I think you got the right advice… that much water pumping is next level energy consumption I’m sure.

  3. Erik Christiansen says

    My rural neighbour has a SWER supply. I always knew it had to be limited, but 5 kVA is pretty slim for a farm. We only had a 3 kVA generator, so even more limited.

    Following Finn’s “Fill the Roof!” policy, I’ve now plonked sixty five 420W panels up there, for 27 kW, so in sunny weather there’s 6.5 kW of free energy going into the BEV, 2.4 kW into the HWS, and a couple of kW into other loads, including the battery, and half the inverters are throttled back as I’m not putting on enough load to challenge the system, even at 12 kW. Still have to add aircon, although insulation and double glazing help a lot. It’s an ideal fit with lots of sunshine, not requiring battery storage as demand tracks production.

    If I’d gone for 3 phase, I could have put 22 kW into the BEV on a good day.
    But I still haven’t figured out how to avoid ending up with potential overload on one phase, but idle capacity on another. Perhaps it’s a matter of distributing potentially concurrent single phase loads across phases, bunching only complementary loads where possible.

    I’ve just noticed that despite a 50A and a 40A sub-board, the main breaker in the main board limits us to 63A (14.5 kW) total, preventing full utilisation of solar generation. That does warrant some thought, as it’s “use it or lose it” when the sun’s generous.

    • Philip Smith says

      I notice you said don.t disconnect from the grid.if you stay connected to the grid but have all this solar and batteries etc how then are you helping to pay for the infrastructure needed for you to stay connected.

  4. I'm Old Gregg! says

    The biggest reason to stay connected to the grid, especially if you are able to install loads of battery capacity, it the ability to feed to the grid overnight, instantly reducing that amount of demand from your old, 19th-century-technology centralised power station.

    Even better if your household batteries can be refurbished to as-new at end of service life.

  5. Geoff Miell says

    The lead graphic with the text:

    Low voltage overhead electric line – property owner’s responsibility

    …is not correct for the Ausgrid region:

    Ausgrid is responsible for building and maintaining the electricity network in the street and supplying power to the connection point on your property. Property owners are responsible for the electrical assets on their property beyond this connection point, including all private power poles, powerlines and pole-top fittings. It is your responsibility to ensure that these poles and powerlines are safely maintained.

    https://www.ausgrid.com.au/In-your-community/Bushfire-prevention/Private-poles-and-powerlines

    • Anthony Bennett says

      Good point Geoff,

      The service fuse is most often the demarcation.

      Upstream it’s the DNSP responsibility, downstream it’s customer owned. Either way they’ll bill you for an upgrade.

      You wouldn’t belive the number of people I had to contact before finding a bloke at the AER who could say the wire downstream of the service fuse, but upstream of the retail meter, is customer owned but a DNSP responsibility. (Tricky if you’d like a customer owned consumption meter in there)

  6. $850 for the united energy truck to disconnect and reconnect.

    40 amp 1960’s cable replaced by a 16mm cable. ~ 25m from boundary point to fuse board.

    Quote 1. $10,500.00 incl truck
    Quote 2. $6,500.00 incl truck
    Quote 3. $4000.00 excluding truck
    Quote 4. $3,600.00 excluding truck

    • Anthony Bennett says

      That’s pretty wild Chris B

      My most recent attempt with SAPN was around $600 for memory. A flat rate they charge which I’m sure was good value when you consider they had a traffic controller to swing a new 3ph loom across the street.

  7. koen weijand says

    not all hybrid inverters can do the power assist mode to support a weak grid.
    sofar none can softluy limit the export when the voltage is nearing it’s limit of 255V. most inverters go in fault mode. work at hand !

    • Anthony Bennett says

      Hi Koen,

      If an inverter can’t ramp down it’s output over 253VAC then it can’t be grid connected in Australia.

      (AS4777:2015 insists cutting output by 5% per volt over 253 and cut out completely after 10 minutes at 258VAC)

      • koen weijand says

        Anthony,

        how does that compare to the AS4777 2020 requirements :
        For export limit control (Clause 6.3), inverters will need to shut down within:

        15 seconds if the soft limit exceeded, OR
        5 seconds if the hard limit is exceeded

  8. Andrew McLauchlan says

    I was considering an induction cooktop but as we are on 3 phase with a limit of 40 amps per phase (rural – distance from pole transformer) we are in a bit of a difficult situation given that the single phase load is 11kw! Maybe they could make some 3 phase sensitive appliances. But a good topic to bring up given that people will be adding bigger loads to the connection

    • Anthony Bennett says

      Hi Andrew,

      You won’t have an issue. Assuming the cook top is a 900mm model like mine, it will have more than one phase connection, so the current is divided. In addition to that, electricians always seem to forget table C-5 in AS3000. Stoves run on a simmerstat, you never have all of the burners on a rolling boil all of the time.

      Stoves and cooktops are diverse. They don’t run flat out all the time. And so it’s quite acceptable to put a 9kW cooktop (a 39 amp load) on a 25amp circuit.

      For your 11kW one, assuming the elements are equally split over two phases, you can have a two pole breaker and parallel 16a circuit to run it.

  9. “But now, with behind-the-meter solar in Australia being so cheap, lots of us want to ditch gas.” You forgot to mention that people also want to move away from fossil fuels, it’s not just about dollars.

    “It’s not wise to go entirely off-grid in the suburbs because grid supply will be cheaper and quieter than the generator you’ll otherwise need. ” You also forgot to mention that exporting and sharing your surplus solar energy with the community will reduce CO2 output. Again, it’s not only about money.

  10. The load balancing EV charger (Zappi) was a way cheaper option for me than upgrading the 32A lead-in once the sparky pointed out I would also have to pay for a board upgrade and traffic management to close the road to hang new cable across it. I just wish I had a way to use the information from the upstream current clamp to turn on smart plugs around the house for other non-time critical tasks when I am exporting. Suggestions welcome!

    • Finn Peacock says

      Have a look at the Catch Solar Relay. Now renamed to ‘Catch Control’.

      • I have successfully been running the Shelly EM3 for a while now to monitor our 3 phase power and to turn the hot water on when there is surplus energy generated. It’s a fraction of the price of the Catch Control and from what I understand from a quick glance at their website, it does the same thing. The Shelly works with or without wifi and can be controlled with an app and also via URL requests.

    • Anthony Bennett says

      John you might look into Home Assistant for more integrations.

  11. Matthew Wright Pure Electric Solutions says

    Agree with Anthony that is our experience. We haven’t found a customer who has complained that we recommended too much solar. We have instead have customers come back for more and even some comment that I should have listened to you the first time and done it once done it right.

    Also we do have some instances in Victoria where customers have 6mm mains they will get the truck roll for free as these lead ins are considered unsafe. You still have to bring your Main switchboard up to standards so you’re looking at $1400-$2400 at least. With the free truck roll depending on your circumstances it may be worth getting 3 phase upgrade. They charge the same for truck roll single phase and three phase. This is in Victoria.

Speak Your Mind

Please keep the SolarQuotes blog constructive and useful with these 5 rules:

1. Real names are preferred - you should be happy to put your name to your comments.
2. Put down your weapons.
3. Assume positive intention.
4. If you are in the solar industry - try to get to the truth, not the sale.
5. Please stay on topic.

Please solve: 29 + 3 

Get The SolarQuotes Weekly Newsletter