Every solar and battery system comes down to three parts: the panels, the battery and the inverter. Everything else is cabling and optional extras. A typical UK home system with a battery costs somewhere between £9,000 and £14,000 at today's prices and usually pays for itself in around seven years, after which it carries on generating for decades, as the systems Spirit Energy installed in 2010 are still doing.
The panels turn sunlight into electricity. Light hits the silicon in a solar cell and knocks electrons loose, and that flow of electrons is the electricity. It comes out as direct current, or DC, the same as you get from a battery. Panels are rated in watts, and a typical panel today is around 450 to 500 W.
The battery stores the DC electricity your panels make during the day so you can use it in the evening instead of buying it from the grid at peak price. Two numbers matter, and people mix them up constantly. Capacity, measured in kilowatt hours, is how much it holds. Power, measured in kilowatts, is how fast it can charge and discharge. Think of a water tank: the kilowatt hours are the size of the tank, the kilowatts are the width of the pipe. The battery is normally the single most expensive component, so sizing it correctly matters more than almost any other decision you will make.
The inverter is the brains. Your panels and battery both work in DC, but your kettle, washing machine and television all run on 230 volt alternating current. The inverter converts DC to AC, and it also manages the flow between the panels, the battery and the house, deciding minute by minute where power should go. You can do this with two separate inverters, one for solar and one for the battery, but a single hybrid inverter running both is cheaper, simpler to install and leaves one brain coordinating the system rather than two.
You do not need all three. Solar on its own runs the house during the day and exports the surplus. A battery on its own charges when electricity is cheap overnight and powers the house when it is expensive. If anyone tells you solar does not work without a battery, that is not true. However, solar on its own will usually deliver a shorter payback period than a battery on its own.
There are three routes, and they are not equal. Understanding the order is the single most useful thing a first-time buyer can take away.
Every unit your panels generate and you use in the house is a unit you are not buying from your supplier. From 1st October 2026 the Ofgem price cap puts average electricity at 26.32 pence per kWh for direct debit customers on a standard variable tariff, so most of your return is simply not handing that money over in the first place.
Panels only save you money while the sun is up, and that is not when most households use electricity. The battery stores your surplus daytime generation and gives it back in the evening, when you would otherwise be buying at peak rates. On a time of use tariff it will also charge overnight when power is at its cheapest, so even on a dull February day you are leaning on cheap units rather than expensive ones.
The third is export, and it is the smallest. Anything you generate but neither use nor store is sold back to the grid under the Smart Export Guarantee. Export rates vary widely between suppliers but sit well below what you pay to import, so exporting a unit is worth noticeably less than using it yourself. Export is a bonus. It is not the thing to build a 25 year investment case on.
One point homeowners often miss: what solar saves you is not income. You are avoiding a cost rather than earning a return, so there is no income tax or capital gains tax on it. Put the same money in a savings account and you would be taxed on the interest.
Cost depends on the size of the system, the property, the equipment and the standard of installation. As a rough guide, a typical home system with a battery lands somewhere between £9,000 and £14,000. Solar on its own starts from around £5,000.
Domestic solar and battery installations are currently zero rated for VAT, so nothing is added on top. That relief is scheduled to end on 31st March 2027, after which the rate is due to revert to 5%. Worth noting for anyone weighing up timing: that is the same date the government's temporary removal of VAT from household electricity bills is also set to end.
For a real example, Spirit Energy installed 22 panels (8.8 kWp) and a 13.5 kWh Tesla Powerwall 3 at Sam's house in Reading in 2024. Sam had been spending £2,040 a year on electricity. In its first year the system delivered £1,869 of value, cutting his effective annual electricity cost to £171. The system cost around £17,000, more than typical for that specification because slate roofs are slow to work on. Even at that price it is on track to pay for itself in 6 to 7 years. His whole project, from first enquiry to a follow-up a year on, is documented in Sam's Solar Journey.
People come to solar with one of two goals, and they pull in different directions. Knowing which one is yours before anyone designs a system will save you a lot of confusion later.
If the goal is the best financial return, you size the system to match how much electricity you actually use, so you are using or storing nearly everything you generate and not paying for capacity you do not need. This gives the shortest payback and the most per pound spent. It is where most people start.
If the goal is self-sufficiency, you size bigger: more panels and a larger battery, so you cover more of your own demand across more of the year, including the duller months. The trade-off is honest. You are buying some capacity you will not always use, your payback is longer and your rate of return is lower. You are buying independence rather than chasing a number, which is a perfectly reasonable thing to do as long as you know that is the trade.
Going fully off grid is a third option that comes up occasionally and rarely makes sense in the UK. The battery needed to carry a house through a British winter with no grid connection at all would be enormous and very expensive. In practice self-sufficiency means leaning on the grid as little as possible, not cutting it off.
Most panels go on a pitched roof, either on roof, where they sit on brackets a few inches above the tiles, or in roof, where they replace the tiles and sit flush. On roof is cheaper and gives more freedom over layout. In roof looks neater and makes real sense if you are re-roofing anyway, since the tiles are coming off regardless.
Flat roofs work perfectly well using a weighted frame angled to catch the sun. If you have the land, a ground mounted array on frames is common for larger and more rural properties. Wall mounting is possible where a roof is not an option, with one catch: a wall mounted panel faces whichever way the wall faces and cannot be tilted, so it only stacks up on a wall facing roughly south, east or west. A north facing wall is not worth it.
The battery can go in a garage, utility room, plant room, or outside on a wall if it is weatherproof. Site it as close as possible to your incoming supply or consumer unit. If your consumer unit is under the stairs, a large battery is unlikely to fit there, so plan for an external wall near the meter cupboard instead. On many newer all-in-one systems the hybrid inverter is built into the battery unit, so there is no separate box to find room for. Where it is standalone, it is normally wall mounted close to the battery or the consumer unit.
What this looks like on your own house comes down to your roof, your consumption and when you use electricity, so it needs designing rather than quoting off a price list. Spirit Energy will put together a quotation for your property, and the technical team will talk it through with you before you have decided anything.