A PV solar electricity system is more expensive than a solar water heating system, varying between £8,000 and £14,000 depending on the type and size of the system you're installing - but the savings are greater too. The Energy Saving Trust estimates that a 2kWp-sized system can save you up to £200 on your electricity bill and provide 40% of your electricity needs a year. Our table compares the savings available from solar water heating and solar PV for a typical three bedroom semi-detached property.
| Alternative energy | Installation cost | Government grant | Cashback | Annual savings for gas | Annual savings for electricity | Total annual income for gas | Total annual income for electricity |
|---|---|---|---|---|---|---|---|
| Solar PV | £8,000-£14,000 | £0 | £725 | £110 | £110 | £835 | £835 |
| Solar thermal | £3,000-5,000 | £400 | £200 | £60 | £90 | £260 | £290 |
Using the table
Savings are based on a three-bed detached house, built 1930-49 with gas or electric central heating. We assume cavity walls, lofts and primary pipework are insulated. Installation costs: indicative cost of equipment and installation.Government grant: maximum available Low Carbon Buildings Programme grant, subject to availability. Cashback: estimated annual income from the feed-in tariff (takes effect April 2010) or renewable heat incentive (from April 2011) for typical installation. Annual savings: estimated for homes currently heated by gas or electricity. Total annual income: cashback plus annual savings.
Types of PV panel
The are three basic types PV panels: monocrystalline, polycrystalline (or multicrystalline) and amorphous. All are made from silicon, but differ in the way the silicon is cut and treated.
To install a system you need to decide how much electricity you want to generate. After submitting details of your property, a PV installer should help you to conduct a site survey and discuss your options with you.
Pros and cons of solar PV
Pros
- Only daylight is needed to create energy – not sunshine.
- Can be connected to the national grid and any excess electricity sold back to an electricity company.
- Can cut average household electricity bill by about 30%.
Cons
- A large roof area is needed to generate lots of energy.
- More expensive to buy and install than solar water systems.
- There's a high initial outlay - typically between £8,000 and £14,000.
- The efficiency of solar panels depends on the number of solar light hours and climate.
- Initial costs are higher than conventional electric and gas-heater systems.
- An unshaded, south-facing location is needed for installation.
- Solar panels can be heavy, so your roof must be strong enough to take their weight, especially if the panel is to be installed on top of existing tiles.
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