Solar panels in the UK: the honest maths

What you are actually buying

A typical home system is around 4kW of panels, an inverter to make the power usable, and increasingly a battery. Installed, the panels-and-inverter package runs £5,000–£8,000 at the time of writing, scaffolding included in any quote that deserves the name. Energy-saving materials carry 0% VAT at the time of writing, already baked into those numbers.

The return arrives two ways. Electricity you use as it is generated replaces units bought at full price: that is self-consumption, and it is where the money is. Electricity you export gets paid under the Smart Export Guarantee at rates that vary by supplier and change often, typically a fraction of the import price. A smart meter is required for export payments, so that box gets ticked early.

Payback, without the gloss

Run the sums on a well-sited roof and most systems pay for themselves in somewhere between 7 and 12 years. Faster if you are home in daylight, charge a car or run appliances on timers; slower if the house sits empty from eight to six and everything exports for pennies. Panels typically carry 25-year performance warranties, so there is plenty of life after payback. Nobody should promise you a date, though, and the good firms do not.

The orientation myth

South-facing roofs generate the most across a year, and the industry spent two decades implying everything else was a consolation prize. Not so. An east-west pair produces a little less in total but spreads it across morning and evening, which is when most households actually use electricity, so more of it gets used at full value. North-facing roofs are the only hard sell.

The battery question

A battery stores lunchtime generation for the evening, lifting self-consumption from roughly a third of your output to well over half in many homes. Whether it pays depends on your usage and tariff: with a cheap overnight rate it can also fill up at off-peak prices and cover the expensive hours. Batteries earn best in homes with real evening load, an EV or a time-of-use tariff, and worst as an impulse add-on.

If you charge a car, panels and a home EV charger are natural partners, and some chargers divert surplus generation straight into the battery on wheels. Solar also nudges your EPC rating upwards, which matters when you sell or let.

Choosing an installer, dodging the circus

Use an MCS certified installer. Without that certification you cannot register for export payments, and the serious firms all carry it. Then get two or three quotes and compare like with like: panel count and wattage, inverter make, scaffolding, bird-proofing, and whether the shading survey was measured or merely asserted.

As for where solar sits in the wider plan: after the free wins and the insulation, which is exactly where the bill-cutting order puts it. Generation is the reward for a house that has stopped wasting.