On 27th August, SI 2026/848 came into effect, legalising plug-in solar in the UK. Shops like Argos now offer them (though rumour has it that Lidl will soon start stocking at about half the price). Earlier this year, we had plug-in solar installed. Although ours is hardwired into a dedicated circuit, the micro-inverter is one that's commonly used in balcony solar kits in the EU. The only real difference is that it didn't come with a plug on the end. Given that these kits have now been legalised and are available for purchase, I thought that it might be useful to write a little about the performance that we've seen so far from our install in the East of England. The Kit The kit consists of: 2 Trina 440w panels A Hoymiles HMS-800w-2T 800w grid tied micro inverter The panels are orientated west and aren't currently optimally placed - their current location was intended to be temporary1, but we didn't get as far as replacing the garage roof this summer. As a result, they're sometimes in shade and lose the setting sun a little earlier than they otherwise would. Performance The array peaked at 81.17 kWh in July: In this data, March and August are both partial months and so report lower. There are some caveats which affect these results though: The UK has been through successive heatwaves this year. Although that's historically unusual, it looks like this will be more common The micro-inverter occasionally cuts off supply if mains-side voltages get too high. This tends to happen in peak times, when our rooftop array (and, presumably, neighbouring installs) push voltage up. In the time that we've had it, the garage install has generated around 315 kWh (£86.63 at current prices). Of course, this is based on peak months and performance will likely decline sharply over the rest of the year. Comparing To Predictions Even with the non-optimal positioning, the savings that we've had are in line with the predictions made in the BBC News article (£70 - £110/year). For their part, pluggedin.solar predicts daily averages of 2.2 kWh for a south facing install. With west facing panels, our observed average sits a little lower: However, the time of year means that we have also seen some very good days: As those days become fewer and further between, it's likely that that average will drift downwards. Proportion of Consumption Ofgem claims (somewhat optimistically IMO) that the average single-rate household uses around 1600 kWh of electricity a year. Ignoring that our 1.53 kWh average will trend downwards, the panels would output roughly 558.45 kWh a year, which is about 35% of that. Slightly more realistically, though, it's quite likely that the majority of the year's generation is already complete. Our rooftop install provides an indication of the rate of tail-off: If we tabulate those figures, we can see how each month ranks against prior months and as a percentage of annual contribution: Val Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec kWh 56.3 84.3 270.3 367.9 421.5 452.0 386.7 337.3 260.9 131.5 58.8 43.3 Vs prev month - +49.7% +220% +36.1% +14.5% +7.2% -14.5% -12.8% -22.7% -49.6% -55.3% -26.3% % of year 1.96% 2.93% 9.41% 12.8% 14.6% 15.7% 13.5% 11.7% 9.1% 4.5% 2.0% 1.5% This tells us that April - August account for around 68.3% of generation. Checking 2024 yields a similar number (69.8%). With August being a partial month, we get a lower figure, but, between April - Aug 2026, the Garage solar has generated 309.34 kWh, so: 1_percent = 309.34 / 68.3 = 4.529 annual = 4.529 * 100 = 452.9 kWh Assuming that the garage panels behave the same way as our rooftop, we should generate around 453 kWh/year (28.3% of Ofgem's average consumption figure). I am expecting that it'll prove to be less though: the garage panels are more prone to falling in shade and need the sun further north than the rooftop ones do. Still, even with that in mind, 400 kWh/year doesn't look like an unreasonable estimate. At 27.5 p/kWh that's £110/year (at the top end of the BBC's prediction), with break-even sat at less than 5 years. Working that back to an average, 400 kWh would give a daily average of 1.10 kWh - which is about half of pluggedin.solar's southerly estimate. Adding To An Existing System If you've already got a solar install and are considering boosting capacity, it's worth noting that these panels still count towards G98 limits. So, if adding a kit takes you beyond 3.68 kW of inverter capacity you'll either need an export limiter or to go through G99 approval. Apparently, some DNOs will still demand G99 even if you have a limiter, so it's worth checking first. Conclusion If the recent change in the law has prompted you to consider investing in plug-in solar, it does look like the outlay will be worth it (especially once prices have settled a bit). Hardwiring meant that our install cost a bit more, but even with that, the system looks like it should break even within 5 years. The energy that it generates is around 25% of the electricity that Ofgem claims an average household will consume. It's a lot less as a proportion of our actual usage, but we're definitely not the average. Thus they will stay there forever ↩