Comparing Solar Panel Generation - East/West split

by @edent | , | 8 comments | Read ~633 times.

We have just installed solar panels on our house in London. We also had panels on our old house in Oxford. How do they compare?

Panel Size4000 Watts5040 Watts
OrientationSouthEast/West Split

Obviously, it's hard to compare exact weather conditions - lower temperature makes for more efficient generation - but I've picked a date in April where both sets of panels seemed to have an unblemished view of the sky.

This is the South-facing panels in Oxford generating 24.28kWh.
Solar generation graph.

And here's the E/W split in London generating 18.59kWh.
Solar graph of London.

London - despite the disadvantageous placement of the panels - generated 75% of the electricity that Oxford did! That's much more impressive than I was expecting. True, the panels have 25% more potential, and are slightly further South, but I was expecting the split to make things much worse.

I've written some code to graph how the different sides of the roof perform. This means I can see how East compares to West. Naïvely, I assumed that the panels not directly illuminated by sunlight would be basically useless. But nothing could be further from the truth!

Here's the split of the above graph.

A graph of two solar generators. Both are fairly even.

Wow! Both East and West generated about the same amount of power - 9kWh.

Given the average UK household uses ~10kWh per day, I could have completely offset my energy use with half the panels!

There are some caveats. Spring is perfect solar weather - long days, cool temperatures, and little tree coverage. Cloud coverage can ruin the generation.

If you're thinking about getting solar panels, but are worried about your roof's layout - I hope this provides some useful information.

You can follow my solar panels on Twitter.

8 thoughts on “Comparing Solar Panel Generation - East/West split

  1. your house must be almost perfectly aligned to the compass!

  2. About 3° off, according to my GPS.

  3. Sam Machin says:

    One of the advantages I can see here is that it also helps to draw out the generation early in the morning and into the evening, we've got all out panels facing almost perfectly south but one of our peak loads is cooking dinner around 7pm, having some westerly panels would help to provide more PV output when its needed. The battery storage helps with this but I don't like running the battery down when it's still quite light out. The extra morning energy is probably less useful unless you're a big cooked breakfast person 🙂

  4. Alan Bell says:

    I had an east/west split, it flattens the curve to use current terminology. It may mean you are exporting less and using more of your generated power, which is a good thing.

  5. Alan Bell says:

    looks like my old system now has per panel data from the microinverters

  6. Could it have anything to do we less air pollution? Our skies have never looked so blue in the centre of London.

  7. LiamJHogan says:

    East and west should (and are, other than timign) be similar. You want to compare to North (idiots!) and South (hurray!) But the point is you make decent energy even with sub-optimal directions.
    Wish they got incorporated by default into new builds. Don’t like the stick-on-tops.

  8. Interesting. Once we get our air source heating in and running (next week) we're turning our mind to panels. Had previously ruled them about b/c of house orientation but e/w is how ours would sit

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