Our domestic solar panels have generated more electricity in a year than we have consumed.
We installed 5kW of solar panels on our roof in 2020. Half are East-facing, half West-facing.
Over a full year, they've generated 4,165kWh.
By comparison, the average UK household uses about 3,800kWh of electricity per year.
But working out exactly how much we've used is slightly trickier. We have a smart meter which reads our import and export. And a generation meter which shows how much we've generated.
Our Import - that's the electricity we buy from the grid - was recorded on our smart meter:
Meter Reading on 2020-03-21 was 1,904kWh Meter Reading on 2021-03-21 was 4,665kWh Total Import = 2,761kWh
Our export - when we sell electricity back to the grid - was also recorded on the smart meter: 2,768kWh.
We exported exactly the same amount as we imported! We are net energy neutral!
How much did we use directly from our panels?
Generated: 4,165 kWh Exported: 2,768 kWh Generated - Exported = Domestic Solar Use 4,165 - 2,768 = 1,397
1.4MWh went directly from our panels into our gadgets. That's about a third of what we generate.
So, our total consumption is:
Import + Domestic = Total consumption. 2,761+1,397=4,158
Roughly, our annual electricity use is 4.1MWh. That's the same as we've generated from our roof.
We got a 2kWh battery a few months ago. It has enough storage to charge up during a summer's day and discharge over night. Ideally, we'd have a couple of MegaWatt hours of storage to charge in summer and discharge all the way through winter. But that tech is a long way off.
We try to run things like the tumble-dryer and dishwasher during the day to make use of the green energy. The big electricity cost is our oven - it's hard to run that during the day if we want a hot meal in the evening.
Our overnight use is a fairly constant 100W - a bunch of smarthome devices and fridge/freezers doesn't take too much. Not many efficiencies to be found there. Some things just need to run continually.
Having spent a year working from home (thanks COVID!!!!) our domestic usage is significantly higher than previous years. WFH means that our computers consume lots of electricity in the day, and our TV & games consoles are powered all through the evening.
In an ideal world, we'd sell electricity for the same price that we pay to import it. Sadly, that's not the case. See "Some thoughts on selling electricity back to the grid" for the details. Basically, we pay 15p/kWh to buy electricity, and we sell it back for 5.5p/kWh. When we sell electricity, the money is taken off our monthly bill.
Over the full year, we've saved about £365. Basically a quid a day. Or, to look at it another way, we've reduced our electricity bills by 60%.
It isn't the most profitable investment - but it makes me extraordinarily happy. And, if energy prices rise, we'll save even more.
We're currently with Octopus Energy (get £50 if you join using that link). They offer a time-of-day tariff. Prices fluctuate based on electricity demand. If we can hook our batteries up to their API, we can discharge the battery when prices are high - and potentially sell back to the grid at a more profitable time.
I blog about our solar panels a lot. But they are pretty boring. They just sit there working. The cost of installation varies depending on where you are in the world and how complicated your roof is. But our small roof generates all the electricity that we use in a year.
This isn't the future - it is now.