DIY Solar in the UK
Matt McCorry, 10 days ago
There are many companies offering to install solar panels. DIY should be an option, as it is elsewhere, but how does it work in the UK?
In short, UK legislation is in line with Europe, but with the caveat that you cannot export power via a 13a plug, it has to be done via a fused spur. Normally the way this is done is an extra circuit is added, protected with an RCBO, then the inverted is connected to the fused spur. More info
Legality in the UK
There are three types of solar installations in the UK:
- G99
- High power installations, require authorisation from grid. Payments for export.
- G98
- Medium power installations, require notification to the grid. Payments for export.
- Sub G98
- Low power (0.8Kw), no notification required. No payments for exports.
How much power can I generate?
If we install 800w of inverter, we could in theory generate 0.8Kw for 12 hours a day, that would be 9.8Kwh. That might be a bit optimistic in sunny Brighton, but I have read of real life users getting 3Kwh a day on an 800w system. You can overpanel to get you closer to the full number, I plan on running 900w of panels with my 800w inverter. The limitation to overpaneling is that the open circuit voltage of the panels combined must be less than the input voltage limit of the inverter. Imagine you have no load on the system, the voltage of the panels will rise until it reaches the open circuit voltage, the inverter needs to cope with this.
Cost
The most basic installation requires:
- 800w solar panels. £80 * 2
- 800w micro inverter. £80
- Mounting hardware. £30
- Minor wiring changes. £100
So all in about £350 to generate 800w. This compares to about £10,500 for a 7.5Kw system with a battery, or £4,100 for a comparable 800w system from Octopus.
You could pay to have a pro install a larger system, and you may assume that it makes more money, but the electricity you consume is more valuable than the electricity you export. 1Kwh costs about £0.25 at current prices. The export price varies, but Octopus offer £0.15 at the moment. An export unit is only worth 60% of one that you would consume. So ideally you want to produce slightly less than your consumption, avoiding generating power the utility company isn't paying you for.