Solar Thermal vs Solar PV: Which Makes More Sense for Lancashire?

Solar PV panels are may offer better long-term value for the vast majority of Lancashire homes in 2026. A 4kW PV system costs £5,200 to £7,800 and may save an estimated £500 to £900 per year through reduced electricity bills and export income. Solar thermal panels cost £3,000 to £5,000 and save an estimated £100 to £200 per year on hot water bills. While solar thermal is technically more efficient at converting sunlight to heat, the economics and versatility of PV make it the clear winner for most situations.

What Solar Thermal Does

Solar thermal panels heat water directly using the sun’s energy. They contain fluid-filled tubes or plates mounted on your roof. The sun warms the fluid, which is pumped to a coil inside your hot water cylinder, heating your domestic water. It is a simple, effective technology that has been used in UK homes since the 1980s.

A typical solar thermal system in Lancashire provides 40% to 60% of a household’s annual hot water needs. In summer (June to August), it can provide almost all your hot water. In winter (November to February), it contributes much less, perhaps 10% to 20%, because Lancashire’s limited winter sunshine and shorter days reduce output significantly.

There are two main types: flat plate collectors and evacuated tube collectors. Evacuated tubes perform slightly better in Lancashire’s cloudy conditions because they retain heat more effectively, but they cost 10% to 20% more. Flat plate collectors are simpler and more durable.

What Solar PV Does

Solar PV panels convert sunlight into electricity, which can power any electrical appliance in your home, charge a battery, heat your water via an immersion heater, or be exported to the grid for payment through the export tariff.

This versatility is PV’s biggest advantage. Solar thermal can only heat water. Solar PV can do anything that electricity can do, including heating water if you add an immersion diverter like the Myenergi Eddi (£400 to £500). A PV system with a diverter gives you solar hot water plus the option to use surplus electricity for everything else.

A 4kW PV system on a south-facing Lancashire roof generates 3,200 to 3,600 kWh per year. With an immersion diverter, the surplus energy that would otherwise be exported heats your hot water tank instead. In summer, this provides most of your hot water for free – the same as solar thermal, but with the added benefit of generating electricity when you do not need hot water.

Cost Comparison

Here is a direct cost comparison for Lancashire installations in 2026:

• Solar thermal (flat plate, 2 panels) – £3,000 to £4,000 installed
• Solar thermal (evacuated tube, 2 panels) – £3,500 to £5,000 installed
• Solar PV (4kW system, 10-12 panels) – £5,200 to £7,800 installed
• Solar PV (4kW) + immersion diverter – £5,600 to £8,300 installed

Solar PV costs more upfront, but the savings and income are much larger. A solar thermal system may save an estimated £100 to £200 per year on gas or electricity used for water heating. A PV system may save an estimated £400 to £650 per year through direct electricity use plus £80 to £300 per year in export tariff income. Adding a diverter captures additional hot water savings of £100 to £200.

Payback periods in Lancashire: Solar thermal takes 15 to 30 years to pay for itself. Solar PV takes 8 to 13 years. Solar PV with a battery takes 10 to 15 years. The financial case for PV is substantially stronger.

Performance in Lancashire’s Climate

Lancashire gets around 1,100 to 1,200 hours of sunshine per year, which is below the England average of roughly 1,400 hours. Both solar thermal and PV produce less in Lancashire than in southern England, but the relative performance difference between the two technologies is similar regardless of location.

Solar thermal panels are actually more efficient at converting sunlight to useful energy – around 70% efficiency versus 20% to 22% for PV. However, this comparison is misleading because thermal energy (hot water) is less valuable than electrical energy. Electricity costs 24.5p per kWh while gas costs 6.5p per kWh, so a kWh of saved electricity is worth nearly four times as much as a kWh of saved gas.

In winter, both technologies produce less, but PV continues to generate useful electricity even on grey, overcast days common across Lancashire from October to March. Solar thermal output drops more sharply in winter because the temperature difference between the panels and the ambient air reduces heat transfer efficiency.

Practical Considerations for Lancashire Homes

Roof space. Solar thermal typically needs just 2 to 4 square metres of roof space – far less than a PV system requiring 15 to 25 square metres. If your roof is very small (common on some Lancashire terraced houses), solar thermal might be the only option that physically fits.

Hot water cylinder. Solar thermal requires a compatible hot water cylinder with a twin-coil design (one coil for the boiler, one for the solar loop). If your Lancashire home has a combi boiler with no hot water cylinder, adding one costs £500 to £1,000, reducing the cost-effectiveness of solar thermal further. PV with a diverter also needs a cylinder with an immersion element, but most existing cylinders already have one.

Maintenance. Solar thermal systems have more moving parts – a pump, a controller, valves, and antifreeze fluid that needs checking every three to five years. Annual servicing costs £80 to £120. PV systems have virtually no moving parts and need minimal maintenance beyond keeping the panels reasonably clean. An annual visual check is usually sufficient.

Freeze protection. Solar thermal systems in Lancashire must have adequate freeze protection because the outdoor pipes can freeze during cold Pennine winters. The heat transfer fluid includes antifreeze, but this degrades over time and must be tested and replaced every five to seven years. PV systems have no freeze risk.

When Solar Thermal Still Makes Sense

Despite PV’s advantages, there are specific situations where solar thermal is worth considering:

Very limited roof space. If you can only fit two or three panels, solar thermal extracts more useful energy from a small area than the same number of PV panels.

High hot water demand. Larger Lancashire families using 150 to 200 litres of hot water per day benefit more from solar thermal than smaller households. The more hot water you use, the more value you extract from a thermal system.

Off-gas properties using oil or LPG. If your hot water is heated by expensive oil or LPG, the savings from solar thermal are proportionally larger because you are displacing a more expensive fuel.

Listed buildings or conservation areas. Solar thermal panels are smaller and less visually prominent than a full PV array, which may be relevant for properties in conservation areas around Clitheroe, Whalley, or the Forest of Bowland where planning restrictions apply.

The Best of Both Worlds: PV-T Panels

Hybrid PV-T (photovoltaic-thermal) panels combine both technologies in a single panel, generating electricity and hot water simultaneously. They are not yet widely available through Lancashire installers, but a few specialist companies offer them.

PV-T panels cost roughly 50% more than standard PV panels and deliver slightly less electricity (because some solar energy goes to water heating) but provide hot water as a bonus. As the technology matures and prices fall, PV-T could become the ideal solution for Lancashire homes that want both functions without using double the roof space.

Can I have both solar thermal and solar PV on the same roof?

Yes, if you have enough roof space. Some Lancashire homeowners install solar thermal on a smaller section (perhaps an east or west-facing slope) and PV on the main south-facing slope. However, using the full south-facing area for PV and adding an immersion diverter usually provides better overall value because PV generates income through the export tariff while thermal does not.

Do solar thermal panels qualify for the 0% VAT?

Yes. Solar thermal installations in residential properties benefit from the same 0% VAT rate as solar PV. This applies to both the panels and the installation labour. The saving is around £600 to £1,000 on a typical solar thermal system.

How long do solar thermal panels last?

Solar thermal panels typically last 20 to 25 years, though the pump and controller may need replacing after 10 to 15 years (£200 to £400). The antifreeze fluid should be checked every three to five years and replaced when degraded. Solar PV panels, by comparison, last 25 to 30 years with virtually no maintenance required.