Which generates more electricity - East- or West-facing solar panels?

by @edent | | 6 comments | Read ~203 times.

We've had our solar panels for exactly a year. Our roof has an East/West aspect - and we have 250kW of panels on each side.

Here's a typical graph showing how each side performs during the day.

What I find interesting is that the side facing away from the sun is much less affected by cloud cover than the side facing the sun. In this example the Easterly panels generation is wildly variable up until midday when the sun passes over the top of the house. At which point, all the light they receive is indirect.

So, over the full year, which side produces the most free-range, organic, small-batch electricity for us?

I had a year's worth of CSV files - luckily Pandas makes it pretty easy to concatenate them all and then do mathemagics:

import os
import glob
import pandas as pd
extension = 'csv'
all_filenames = [i for i in glob.glob('*-strings.{}'.format(extension))]
combined_csv = pd.concat([pd.read_csv(f) for f in all_filenames ])
combined_csv.columns = ["Time", "East", "West"]
total = len(combined_csv)
(combined_csv["East"].sum() / total) * 6
(combined_csv["West"].sum() / total) * 6

East generated 2,130kWh.
Wast generated 2,254kWh.

So West is roughly 5% better at generating electricity than East. But there isn't much in it. The data isn't completely clean - sometimes my monitoring software was down for a few hours. I'd put that 5% within the margin of error of the accuracy of my measuring system.

Basically, don't be put off if you can only have panels on one side of your roof.

6 thoughts on “Which generates more electricity - East- or West-facing solar panels?

  1. Alan Bell says:

    I figured I consumed a higher percentage of my own electricity from the west facing panels when I had them. Doesn’t matter if you have a battery of course.

  2. @Edent interesting! It would even more interesting also a south comparison. Change roof accordingly 😜

  3. JohnU says:

    Must be a big roof to fit 250kW per side.

    1. @edent says:

      Not really. You can see some pictures on Relaunching @edent_solar. Part 1 – installation.

      Photo of our roof. 8 Panels are installed.

  4. Mark Duncombe says:

    Interesting stuff. Does having an East/West split compared to south only impact EV charging? Does it result in a smaller window where an EV can be charged?

    1. @edent says:

      I written a fair bit about solar charging an EV.

      In short - don't worry too much about it. Electricity is fungible. There's no noticeable change in "window". But it rather depends when you park your car at home.

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