Heating water from the roof is priced differently from making electricity there, because the collectors are the cheaper half of the job. What moves a solar thermal quote is the plumbing: a twin coil cylinder the system can charge, a pump station, a controller, and a route for the pipework from the roof to wherever that cylinder stands. A house that already has a suitable cylinder and a house with a combi boiler are quoted for two different jobs under the same name, which is why two prices for the same collectors can be a long way apart.
What a typical system costs before anybody looks at your roof
The Energy Saving Trust puts the cost of installing a typical solar water heating system at around £5,300, and names the two things that move it: whether you choose evacuated tubes or flat plate collectors, and how large a system you fit. Treat that as the middle of the range rather than a quote. It assumes a straightforward house with somewhere for the cylinder, and the two houses that fall outside it are the one with no cylinder at all and the one where the collectors are a long pipe run from the tank.
Solar water heating panels prices: UK quotes and the parts they leave out
A comparable quote has the collectors, the mounting and roof penetrations, the twin coil cylinder or the reason the existing one will do, the pump station and controller, the pipework and its insulation, the commissioning, and the MCS paperwork as separate lines. The parts that get left out are usually the cylinder and the space it needs, the scaffold or tower for the roof work, and making good the airing cupboard the tank now fills. Ask which of those are in the number and which are assumed, because the cheapest quote is often the one assuming the most.
Flat plate solar collector or evacuated tube, and what each does to the price
A flat plate collector is cheaper per square metre, sits lower on the roof and is harder to damage. Evacuated tubes cost more, are insulated by their own vacuum so they hold on better in cold and overcast weather, stand further off the tiles and can be repaired a tube at a time. Neither is the right answer everywhere. On a roof with plenty of south facing area the cheaper flat plate usually wins on price for the same output; on a small or shaded roof the tubes buy back some of their cost by needing less of it.
Solar hot water system cost against PV with a diverter
The comparison most households actually face is not tubes against flat plate, it is thermal against photovoltaic panels with a diverter sending spare electricity to the immersion. Thermal is better at heating water and can do nothing else with the sunshine. PV is worse at heating water and can run the house, charge a car or be exported. Where hot water demand is high all year and a cylinder already stands there, thermal still adds up. Where it is a small household with a combi boiler, the same roof area spent on PV is usually the better buy.
Hybrid solar panels, which try to do both jobs on one panel
A hybrid, or photovoltaic thermal, panel puts a water circuit on the back of a PV module, so one panel makes electricity and recovers the heat the cells would otherwise waste. It uses roof area well and it cools the cells, which makes them slightly more efficient. The catches are price, a much shorter list of installers who fit them, and a system that has both a thermal circuit to service and an electrical one to inspect. It is worth pricing where roof area is genuinely the binding constraint, and rarely otherwise.
What the system costs to keep after it is in
Unlike photovoltaic panels, a thermal system is a pressurised circuit with a pump, a controller and a heat transfer fluid that degrades, so it has a running cost. The Energy Saving Trust recommends a thorough check every five years to flush the system and replace the fluid mix, with a shorter annual check worth considering. A system left alone for a decade is often found not working at all, and the owner finds out when the boiler bill does not fall. Ask at quote stage what a service costs and whether the installer does them.
Questions people ask about solar thermal panels cost
Is solar water heating cheaper than solar panels?
The collectors are usually cheaper than an equivalent area of photovoltaic panels, but the installed system is not always, because the cylinder, the pump station and the pipework carry cost that a photovoltaic array does not. Price both for your own house rather than comparing the panels alone.
Do I need a new hot water cylinder?
You need one the system can charge, which normally means a twin coil cylinder with a dedicated coil for the solar circuit. A single coil tank usually has to be replaced, and a combi boiler system has no cylinder at all, so one has to be fitted and found space for. This is the single largest variable in most quotes.
How much of my hot water will it cover?
The Energy Saving Trust says a system normally provides roughly half of a household's hot water over a year, nearly all of it in summer and much less in the winter months. The boiler or immersion covers the rest, so the system reduces a bill rather than removing one.
Does the installer have to be certified?
For the grants, the warranties and the consumer protection to mean anything, use an installer certified by the Microgeneration Certification Scheme for solar thermal specifically, not for photovoltaic alone. It is a different certification and a different skill set, and the trade has far fewer firms doing it than doing PV.
How many quotes should I get?
The Energy Saving Trust recommends getting quotes from at least three installers. Ask each of them to itemise the cylinder separately, because that is where comparable looking prices most often turn out to be describing different jobs.