Best side of the roof for solar panels - NE or SW?



We’re looking to install 6.6kw of panels with a 5kw inverter on our house in Adelaide, but we’re getting conflicting advice from installers as to the best side of our roof to install the panels on.

Our narrow house faces north-west, meaning our two main roof faces are north-east (54 degrees from north) and south-west (126 degrees from N).

We use most of our power after 5pm on weekdays. There are no shading issues.

I would be grateful for your view as to which roof face is preferable for the panels - NE or SW? Or some panels on both sides?

Thanks for your help!




Hey @John_FC

This is an interesting one, because intuitively I would say NE. It will clearly give you more sun throughout the year, by my rough calculations an extra 1500kWh per year (9200 vs 7700 for the SW roof). Assuming an average roof pitch of approx 25 degrees, you’ll get about 25kWh per day on average from the NE roof, and 21 from the SW roof.

However, the fact that you use most of your power after 5pm puts an interesting spin on it. It really depends on how much power you use when, as to what would be more financially beneficial. Do you know how many kWh you use per day on average, and a rough % of how much you would use in the evening before the sun goes down?

Let’s hypothesise that you utilise 10kWh of your own power with a SW install, but only 3kWh with a NE install, and that you get 10c/kWh for the power you export and you pay 25c/kWh when buying from the grid.

With a NE install you will export 22kWh at 10c, and offset 3kWh at 25c = $2.95 per day.
With a SW install you will export 11kWh at 10c, and offset 10kWh at 25c = $3.60 per day.

You would be better off in that scenario with a SW install. However, of course I’m just pulling numbers out of the air, and thinking of the best possible scenario for the SW install. I doubt you would be able to use that much more of your own power from a SW install.

One last thing to consider is whether you might get battery storage in future. In that case, you will probably want to maximise your generation.

Hedging your bets and splitting it across both roofs seems like a decent option to me.

All the best, hope that helps. Please let us know what you decide, and also let us know which company you went for and what the experience was like if you don’t mind. Some photos would be good too.

Also, if you haven’t already, it’s worth taking a look at our Guide To Buying Solar before locking in any quotes.

Cheers, Marty