Fifteen MegaWatt Hours from Sunshine - Four Years with Solar Panels in London

Just as the UK was entering the first COVID19 lockdown, we got solar panels installed on our roof.

Four years later and our generation meter shows they have produced 15,480kWh of electricity.

That's a rather impressive 3,870kWh per year.

This is what the average UK household uses in electricity:

Our roof is non-optimal. We have an East/West split rather than the more usual South-facing panels. We have some big trees near us. And we live in a rainy, cloudy, overcast region of London.

We still produce more than the average household consumes!

Depending on the Carbon Intensity of the UK grid, we've saved about 3 tonnes of CO₂.

Imagine if we could put solar on the roof of every house in the country. Domestic consumption from the grid would fall to zero on sunny days. Even in winter it would dramatically reduce usage. If you can add a battery and smart meter then domestic costs would plummet.

Money

Let's talk about money for a moment. I don't know how much it will cost you to put solar panels up on your roof. You might need lots of scaffolding, your wiring and consumer unit may need an upgrade, there might be bats in your loft. Get a couple of quotes and find out for yourself.

But I can talk about how much money solar panels can save.

Over the last 4 years, UK electricity prices have fluctuated considerably. Somewhere between 20p/kWh and 30p/kWh. That means those 15,480kWh are worth somewhere between £3,000 and £4,600.

Of course, not all of that electricity gets consumed by us. Some of it flows back to the grid. As a rough rule of thumb, most systems seem to export half of what they produce.

Octopus Energy (join and we both get £50) pay 15p/kWh on export.

So let's say 50% is used, saving 25p/kWh, and 50% is sold at 15p/kWh. That means we have profited by roughly £3,000 over 4 years.

Data

Every day at sunset, I automatically publish data straight from the solar inverter. You can grab the data from GitLab. It will show you real data, changing every 5 minutes, and could be useful if you're modelling something.

My previous dataset from the last house we lived in has been used in a number of academic studies.

Solar panels are great for geeks! I deliberately got an Inverter with a local API & Ethernet connection.

Should I get solar panel?

Photovoltaic cells are the ultimate in "boring magic". Stick them on your roof and forget them. Year after year they'll happily sit inert, chugging down photons and spitting out electrons. The rain washes them clean. The warranties are generous. The technology behind them is stable and well understood. All you have to do is watch your electricity bills fall.

If you've enjoyed this post, consider joining Octopus Energy using my referral link - they have great tariffs for solar panels.