Solar FAQ

You're probably here because you saw an auto-post from my solar panels. Yes, that's right, I've wired up the sun to the Internet of Things!

Here are answers to some questions I get asked about them. If you've got any others, please stick them in the comments section or ping me a message.

Where are your panels?

In 2020⁰, our current panels were installed in South East London, UK. They are an East / West split.

How much do they generate?

It varies but, on a good day over 24kWh. In winter, it can be less than 1kWh.
On average, about 3,780kWh per year
You can run a simulation for your own property.

Can I get the data?

Yes! All the data from the London panels is Open Source.
You can also get 5 years' worth of data from our Oxford panels. That dataset has been referenced in several academic papers.

This isn't a sensible question to ask. My home has 3 storeys and needed scaffolding back and front - your home is a bungalow. My electrical wiring was pristine - you needed a full rewire. I paid extra for an Internet connected inverter - you went with the cheap model. Your installer had a discount on batteries - mine was installed afterwards.

Go ask a few local installers for quotes. Speak to your neighbours with panels to see who they recommend.

What's the payback rate?

What's the payback rate of getting a new kitchen installed? Or buying a new car?

But, very roughly, about 7-10 years depending on electricity prices. When prices go high, we save more money.

The sums are complicated, but on average we pay 12p / kWh for electricity. When the sun is shining, our electricity costs are zero. If we produce more electricity than we can use, we sell it back to the grid. At night - or when power is expensive - the battery discharges and saves us money.

Have you considered…?

A heat pump? Read why we can't have an air source heat pump.
An iBoost / hot water heater? We used to have one, but they're a bit useless. We don't need hot water when the weather is warm, and we'd rather fill the battery or sell the electricity.
An electric car? We used to have one, but then moved house and now live near a bus stop. But if Vehicle-to-Grid ever comes in, I'll consider it.

Can you go off grid?

Not really. If there's a power cut, the inverter stops feeding energy back into the grid lest it electrocute someone.
We have a separate Uninteruptable Power System which charges from solar and powers all our essentials.

How do you draw the graphs?

I have a Raspberry Pi which regularly queries the inverter. It saves the data and draws a graph at sunset. You can read about how it works and I've made the program open source so you can grab the code from GitHub.