The house is a detached 3-bed 1960s bungalow in Sherborne’s West End.
Insulation
- Cavity wall insulation (c20 years old)
- Loft insulation 300mm
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Systems installed 9with date of installation)
- Solar PV 4Kw (2012)
- Air Source Heat Pump (2020, Dorset Energy Solutions)
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Solar PV
Eight panels, providing a nominal 4kW are installed on the west-southwest facing roof. The panels work best on sunny afternoons+evenings but nearly always generates something, even on overcast days; on the best day the panels produced 28kWh. Income from the Feed-In Tariff provides 28p/kwh. Income is c£1200/year
while the installation requires no regular maintenance:
Storm damage to roof in 2020 meant that three panels had to be replaced. This was covered by insurance.
The Inverter failed in 2021 (after nine years). The replacement cost £500 and the owners advise always shopping around when replacing any components.
The oOwners are moving shortly, but if staying would invest in more PV panels and a household battery for energy storage.
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Air source heat pump
9Kw heat pump. No new radiators were needed as four double-fin units had been fitted in 2008. The heat pump installation cost £10,500, including iBoost to use excess power from the PV panels to heat water. iBoost provision gives free hot water from April to the end of October.
The electricity bill is typically £20/month from March to September, though electricity consumption varies greatly according to season: eg the figure for April was 217kwh, while July consumption was down to 48kwh.
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Helpful owner tips
Adjusting heat pump to heat water to 50C (instead of 55C) has given more economical running – hot water is topped up by iBoost/PV panels so heat pump kicks in less often.
Additional heating via night storage heaters (one in hall, one in rear of house) takes advantage of cheaper overnight tariff – especially useful for heating north-facing back of house in daytime.
Use economy setting on washing machine and dishwasher – it takes longer (around 3 hours for washing machine) but lower power consumption means it can be covered by the PV panels (and that means washing for free) even on a cloudy day.
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Conclusion
Well worth doing.
