Analysis: How ‘plug-in solar’ can save UK homes £1,100 on energy bills

§ Plug-in panels

Compared to rooftop solar, smaller plug-in solar systems consisting of one to two panels can be easily installed on balconies, in gardens and other outdoor spaces. They can be plugged directly into home sockets without the need for additional wiring, reducing electricity taken from the grid and thereby cutting bills.

Plug-in solar has already taken off in Germany, with official registrations already exceeding 1m installations (the actual number could be up to 4m). Other growing markets include France, Spain, the Netherlands and the US.

Panels could be available in the UK “within months” at retailers, such as Lidl and Sainsbury’s, according to the government. (Many of the products from EcoFlow, one of the main providers of plug-in solar in the UK, are already sold out online.)

The government said it will work with relevant bodies to update electrical regulations to allow the use of plug-in solar. The Institution of Engineering and Technology (IET) has advised homes to get their wiring checked before installing.

§ Costs and benefits

To assess the potential impact of plug-in solar, Carbon Brief conducted a cost-benefit analysis for an 800-watt (W) installation in a typical two-to-three bedroom home in London. The assumptions are approximate and will vary for different locations and set-ups.

Optimally placed panels – south-facing and tilted at around 40 degrees – would generate around 820 kilowatt hours (kWh) each year in London – at a “load factor” of 12% – according to the EU’s PVGIS database.

Actual output is likely to be lower, due to sub-optimal placement – such as vertically on balconies – as well as orientation and shading.

A report by trade body Solar Power Europe noted these factors could cut 30-60% from optimal output. This analysis assumes a 45% reduction from optimal output.

If a household is able to use 90% of the output – typical for such installations – then the panels would provide 400kWh of electricity each year, enough to meet 15% of typical demand.

This will vary on the household usage patterns, but running appliances such as washing machines during peak daylight hours could improve capture rates.

This could save £110 on electricity bills each year, meaning the upfront cost of around £500 could be paid back within 5 years, according to Carbon Brief’s analysis.

Assuming the panels last 15 years, total net savings over their lifetime could reach £1,100.

These savings assume a fixed unit cost of 27p/kWh, based on predictions for July 2026.

If electricity prices surged to 34p/kWh for a prolonged period – as they did during the 2022 gas price crisis – then annual savings could increase to around £140, further reducing the payback time.

If module costs fall over time as more suppliers enter the market, this could reduce the upfront cost and payback time.

If 3m households take up plug-in solar – comparable to Germany’s current deployment – this would generate 1.2 terawatt hours (TWh), less than 1% of UK demand.

While this would not significantly cut UK emissions overall, it could still save the households more than £330m in total and avoid around two tankers’ worth of imported liquified natural gas (LNG) each year, according to Carbon Brief’s analysis.

§ Unlocking participation

Aside from its economic benefits, plug-in solar could unlock participation in the clean-energy transition for a wider percentage of the population.

For example, renters make up around one-third of UK households and lack control over the installation of rooftop solar and heat pumps. Plug-in solar would enable them to engage in and benefit from clean energy in their homes.