Six Months of Solar Power Stats
By @edent
· solar · 5 comments · 350 words · read ~281 times.
We've had our new solar panels for 6 months. Here's how they've performed over summer.
3,361 kWh Generated
2,445 kWh Exported
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916 kWh ConsumedDespite working from home every day, using laptops, monitors, microwaving lunch, we only used about 5.5kWh of solar each day. About 72% of our summer generation was sold back to the grid.
According to our electricity provider, in those 6 months, we imported 992kWh of electricity. So the solar panels reduced our energy bills by 50%. That saved us about £120 buying from the grid, and we sold the excess for about £136. Giving us a pleasing saving of £256 so far.
Very roughly, we used (992+916)=1,908kWh over 6 months. That's 10.4kWh per day.
According to official statistics, the average UK domestic electricity consumption in 2018 was 3,831kWh. About 10.5kWh per day. We're bang on average!
There's a limit to how much power we can use while the sun is shining. We can set the dishwasher, tumble dryer, and other appliances to gobble up power during the day. But we use an electric oven in the evening, have lightbulbs and TVs on, and need an electric blanket in winter.
Here's a graph of a typical summer's day usage. 
Once the sun comes up, our electrical import drops to virtually nil. Once we hit sunset, our import rises as we turn on games consoles, run a hair dryer, and cook dinner.
So, the next obvious step - get a big battery!
Regular readers will remember that in our last house we we installed a Moixa battery as part of a local energy trial. We're preparing to get an upgraded version installed in our new home.
That should allow us to save our excess energy and then use it overnight. The plan is that the battery will charge during the day - so we can use its electricity overnight. Over summer, it should take our import almost to zero. But how will it fare in winter? Subscribe to the blog to receive updates!
So neat!
Or you could get a haircut, thereby reducing your reliance on the hairdryer.
I can ban you from commenting, you know!!
Andy says:
So in the UK, Can you install this system yourself and put power back into the grid? In the US you can't unless a contractor does the install and it is all verified, which kind of inflates the price exponentially. I work with similar battery powered systems and had always wanted to do something like this, it would have to be stand alone though for me. I'm curious as to how long you will have to stick with it to break even. I ended up here on your 2015 xbox controller/pi zero blog that i have turned into a project all of my own 🙂 I should probly just read more into what your doing! Cheers!
Not quite. In the UK, you need a professional installer. Obviously, that adds labour costs. But you'd have to pay for the scaffolding etc anyway. With anything electrical, you should get a certified and insured professional to do the installation and sign it off.
Payback time is complex. Different countries have different subsidies available. We expect the system to pay for itself in 10-15 years. But I'm more concerned about the ecological impact than the economical one.