PRACTICAL GUIDE · UPDATED 2026-10-30

Solar electricity, solar hot water and batteries: what each does

Solar PV generates electricity; solar thermal heats stored water. Compare each system against your roof, energy use and tariff terms.

Solar PV panelsDaylight generates DC electricity.

InverterDC is converted into household AC electricity.

Your homeUse electricity as it is generated.

Surplus generationOptional battery storage or export to the grid.

Where solar electricity goes. Solar PV makes electricity. Solar thermal is a different technology that heats water. Normal grid-connected PV usually shuts down in a power cut unless designed for backup.

Solar photovoltaic panels, usually called PV, convert daylight into electricity. An inverter makes it usable by household appliances. Generation varies with sunlight, roof direction, shading and season; panels can generate on cloudy days but do not provide a constant supply. Power used in the home at the time it is generated reduces imported electricity. Surplus can be exported or stored if suitable equipment is installed.

Solar thermal is different: roof collectors transfer heat through a fluid circuit to a suitable hot-water cylinder. It normally supplements another water-heating source and does not generate electricity. Most domestic systems serve taps, showers and baths rather than radiators. Winter output is lower, so backup heating remains important. Cylinder space, household hot-water demand and compatibility with the existing boiler need assessment; a standard combi installation cannot simply accept a solar thermal cylinder without a designed solution.

For PV, distinguish total generation from the amount used at home. A useful starting calculation is self-consumed solar kWh × avoided import price + exported solar kWh × export price. This estimates annual energy value before equipment, finance, maintenance and replacement costs. Do not count the same kWh as both self-consumed and exported. Ask for roof-specific generation and self-consumption estimates, with the assumptions shown.

Under the Smart Export Guarantee (SEG), eligible generators apply to a participating supplier for export payments. Ofgem says SEG rates must be above zero, but suppliers determine their rates and contract lengths. Your export supplier can differ from your import supplier. Check certification, export metering and application requirements, then compare the combined import and export deal: a headline export rate does not establish the cheapest overall arrangement. Check the supplier's written conditions for battery exports and any linked import tariff.

A battery shifts electricity from sunny or cheap periods to later use. It adds purchase cost, energy losses and eventual replacement; usable capacity, charge/discharge power, warranty and your evening demand matter. Compare the avoided import cost with the export income forgone, allowing for losses, and request quotes with and without storage. An ordinary home battery does not carry summer surplus through winter. PV can help power a heat pump, but winter and night-time heating will still need grid electricity.

Before ordering, request a site assessment of roof condition, shading, electrical installation and grid-connection requirements, followed by an exact itemised quote. Ask separately about inverter and battery replacement, monitoring and warranties. Model savings under more than one tariff; no bill saving or payback period is guaranteed.

Your checklist

Specify PV electricity or solar thermal hot water when requesting advice.
Ask for annual generation, self-consumption and export estimates separately.
Compare supplier contracts and check SEG eligibility and metering requirements.
Compare solar alone with solar plus battery using losses and replacement costs.

Sources & further reading

General information, not a property assessment, booking or assurance about a listed business. Dates indicate content updates; they are not invented publication dates.

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