Solar Panel Orientation: Is West the new North?

Here’s a very common question that comes in to SQ HQ.

“My roofline is North/South, so my roof areas face either East or West. I know North Facing is ideal, but I don’t have a North facing roof! Should I put my solar panels on the East or West Facing roof (or both) ?”

Short Answer: Probably West

Longer Answer: In terms of the amount of power produced, facing your panels East will produce exactly the same amount of power as facing them West.  In either case you’ll generally take a 10-15% power hit compared to having them facing the ideal direction (North).

Compass

Is North always the best direction for solar panels?

So why do I say “probably West” as the short answer to the question?

Well, the reason I err on the West facing roof is because that part of your roof will get the sun later in the day. An East Facing solar array will generally produce its peak power at 10-11am. A West Facing array will produce its peak at closer to 2pm.

Most people use more energy later in the day. And most people want to use as much of their solar energy as possible, without exporting it. Why? Because at the time of writing most Feed In Tariffs give you less per kWh if you export the electricity than you pay for imported electricity. So most people will pay off their solar system quicker if they minimise exports.

Here’s a much more detailed explanation of how solar energy is exported depending on the time of day.

So if you face the panels West, and you are a typical family (in terms of electricity usage patterns anyway!), and your FiT is less than your retail electricity price, then West facing Solar Panels makes more sense than east facing.

In fact, if you live in a State with a really miserly FiT (hello NSW & WA !) then it may actually make more financial sense to face your solar panels West rather than North! To work out if this is the case you’ll have to get a good feel for when in the day you use electricity, then estimate how that will affect what % of solar power you export. Then you can use my solar power payback calculator to see which configuration pays back quicker.

Or if that sounds like too much trouble – you could always engage a good solar power sales person / installer to do the analysis for you. And asking them to do this is a great way to filter out the not-so-hot sales people out there!

Time of Use Electricity Pricing is Coming!

One more reason to consider West facing panels is that many people (me included) believe that in the near future everyone will be forced on to Time of use (TOU) electricity pricing where you pay differing amounts per unit of electricity depending on when you use that electricity.

For example Energy Australia‘s weekday TOU tariff costs 18c per kWh from 8am to 2pm, and a whopping 44.7c per kWh from 2pm to 8pm.

If you were on a similar tariff, it could make a lot of sense to push your solar power generation to later in the day, where every kWh of solar power you use is worth 2.5 times more!

The key is to find a solar installer or salesman that understands this stuff.

All this talk of Feed In Tariffs, TOU tariffs, and solar panel orientation can start to overload your brain when you combine it with trying to choose an installer and solar panel and inverter hardware. I feel your pain! The answer, as I mentioned above is to find a solar company that asks the right questions:

1) What times of day do you use your electricity?

2) How much do you use?

3) What kind of electricity tariff are you currently on?

So that they decide which panel orientation is right for you based on numbers (not a Wild Assed Guess!) and also so they can provide accurate payback calculations that take into account the ridiculously varied Feed In Tariffs in every state.

About Finn Peacock

I'm a Chartered Electrical Engineer, Solar and Energy Efficiency nut, dad, and founder of SolarQuotes.com.au. My last "real job" was working for the CSIRO in their renewable energy division.

Comments

  1. Was told by an installer/sparky recently that West-facing cells get hit with heat coefficient losses (metal roof) because when the sun hits them, they are already hot from higher afternoon ambient temperature plus temperature of roof. East facing in the morning the panels are cooler so you will get less losses from heat de-rating…

    Guess it depends too on size of system and the corresponding savings involved.

    Most installers/suppliers seem pretty lazy and/or dopey/greedy when it comes to sun angle and orientation. They will usually just slap them on your pitched roof without optimisation for sun angle. Most sparkies seem too lazy/greedy to fit tilt frames, because they want to make $2000-3000 for only a day or two of work.

    Had a bloke on my roof with me the other day and I have flat section of roof (about 40 metres square), and pitched sections of various orientation for the rest of the roof . Even though the flat section faces east, it would be best to fit tilt frames and then they would all face north. He wasn’t keen at all to fit them and suggested east instead. Although he said the costs outweighed the benefits…

    Now I had a look at a figure with sun angles, orientation and efficiencies, and east-facing would be maybe 80% efficient (23 degrees pitch) ? Considering the Qld FIT of $0.44/kWh that would mean about $128/year difference per kWp. If I can fit 2 kWp on the flat section, that is $256/year. If based on $0.25/kWh charged for consumption about $73/year per kWp or $146/year for a 2 kWp system. Over 16 years (until 2028) for $0.44 FIT that’s 16 x $128 = $2048. For 2 kWp that’s about $5 000.

    Even with no FIT and 10% increase per year for power starting at $0.25 kWh (2012) that’s $1 274 over 30 years per kWp.
    Cost for tilt panels – DIY is around $60 (eBay), and around $85 installed per panel (based on one quote). So that’s $240-$340 per kWp (4 x 250W) so you’re up by $900-$1700/kWp for the extra expenditure (cash basis). For 2kWp that’s $1800-3400 return on investment over life of system or rebate period for ~$500-700.

    Moral of the story – (pretty much) everything you are told is bullshit – you can only rely on your own research from informed sources. And do a lot of hours in the process.

  2. David Maddern says:

    A very important factor is not considered here… local clouding. In Tassy (where I lived) it clouded to the west on the mountain. Where I am now in SA it soon clouds in the morning and it is worth getting this kind of knowledge for the whole year for your site. from personal observation and talking to old blokes in th area and even ask weather people’s opinions and make an intelligent decision with all the factors onboard.

  3. Greg Mcilwain says:

    I live in Townsville, skin cancer capital of Austrlalia but I have a 3 degrees pitched roof and have mounted my string of 11 Qcells 235 W panels in two rows near the western end of my roof cause the morning sun is blocked by Mt Stuart Range and trees along Ross River. I was first easing for a reasonable pitch that I was first quoted on but changed and opted for the 11th panel. It seems from reading several of ur recommendations that I’m on the right tracks. However with a low 10 month rainfall and next to the main road and dirty fruit bats my panels get very dirty very quickly, what if any, can i do. Also would a cheap brand ‘x’ degreaser be Ok to spray them with before I hose them down. I have been brushing them with a horse hair broom while hosing them up till now.
    Thankyou for your common sense answers on your webpages. God bless you too.

    • Hi Greg,

      No degreaser – just water to hose down the panels – any additive is likely to leave a film which will reduce performance.

      You need to use soap to remove bat poo etc, then make sure no soap residue is left on the glass.

      Hope That Helps,

      Finn

  4. Hi,
    I am in the process of getting Solar Panels installed on my roof. The front of my house faces north. The sales person suggested I install a 2.2kW system with 12 panels . The techs rocked up on my door step and informed me that they will not be able to fit 12 panels on the front roof (lack of roof space) and suggested that I split the panels- 6 facing west and 6 facing east. They have offered me a Dual tracking inverter.
    I am now a bit worried about the efficiency and have read on multiple sites that it is ideal to install the panels facing the north. The techs have assured that they done similar setups(east and west panels) for other customers and the result was good.
    I have been searching the web for reviews on a similar setup but have not been able to get a decent review
    Does anyone have any suggestion?
    I have clearly informed the installers that if the setup is not efficient in terms of power generation then I will not make the full payment and that they will need to relocate the panels.
    Any suggestions would be highly appreciated.
    Thank You

    Note: Not sure if I am posting this in the right area.

    • Hi Nicholas,

      AS long as you have a dual tracking inverter you should be fine. Yes – the west facing panels may generate about 15% less energy than if they were on the North face, so overall your energy yield may be about 7% down compared to all north facing. But… as explained in the blog post above you will probably save more money with some west facing panels because you will generate power longer into the late afternoon/evening when you are more likely to use it in the house and save approx 30c per kwh compared to exporting it at 8c per kWh.

      Hope That Helps,

      Finn

  5. I was advised by a solar salesman that as I only had the option of an east or west facing roof option I should put half on the east side and half on the west side – from my research so far I thought the best panel only performs as good as the worst (e.g. if some panels are shaded) therefore with this option would I not loose on a double whammy basis – not getting peak output unless the sun is directly overhead? (Cairns QLD)

  6. Crunch Time !! I have an existing array SB 1100 with what I believe are 6 suntech panels using the only available north facing roof area. It would be my intention to install a SB 3800 with the maximum number of panels allowed Hanwha) – half facing east,half facing west.(no shade problems).We have 2 X 250 litre hot water units (3600 Watt)(house & Bungalow – is it feasible to put these on timers to only heat during daylight hours ( one AM one PM ) i realize they would still take power from the grid.Many thanks Finn

  7. im part way through redoing my whole solar set-up. everything from replacing the cabling from the PV array to the controllers (was ordinary 240v house wiring) with proper rated PV cable. my issue is i have limited space facing north that is usable for mounting panels. am able to fit 5 panels in the space provided, so i made the call to mount another array on the west side. should i just put them all on the west facing roof or is splitting them up like that ok?each array has seperate cabling joined at a ‘j’ box prior to going to the batteries/ controller. I also have purchased 200w panels as 90% of the existing panels are 200w mono’s, there are however 3 165w poly panels in the mix. should i mix and match them or replace these with more 200w ones?? thanks

  8. I have solar panels with east west configuration with a twin input inverter at Wynnum West. Performing well above what I had thought I would get. There are 14 panels 7/7 about 200watts each

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