Wind turbine

Installed on the roof or, for bigger turbines, on a mast in the garden. Great on windy coastlines or mountains, but not in towns or cities. May need planning permission.

Cost? Depends on size: from £2,000 up to £20,000 for a system that covers a household’s entire electricity demand.

Payback time? Eight years or more.

Solar photovoltaic electricity

Solar panels generate electricity as the sun's rays hit a silicon layer.

Cost? Varies with size: perhaps £10,000 for a household system. If you generate surplus electricity, you can sell it back to the grid.

Payback time? More than 20 years.

Solar water-heaters

Collects warmth from the sun, heating water, which is then pumped through a coil in the hot-water tank. Best on south-facing roofs. It requires a hot-water storage tank and, in the UK, there is only enough sun to let you switch off the boiler six months a year.

Cost? Typically £2,000 to £4,000.

Payback time? More than 20 years at current gas prices.

Better central heating controls

Inefficient controls mean many households waste energy. Look at intelligent alternatives such as the Dataterm, a combined thermostat and central heating programmer.

Cost? About £500 for a completely new installation.

Payback time? About seven years.

Condensing boiler

Up to 30% more efficient than traditional boilers at converting fuel into heat.

Cost? About £1,500.

Payback time? Eight to 10 years.

Insulating your loft

Increase it to a thickness of 25cm. The greenest insulating material is sheep's wool, but you can buy standard material from DIY stores. Foam backed with aluminium foil is the high-tech option.

Cost? A few hundred pounds.

Payback time? Two or three years.

Insulating walls

Cavity-wall insulation is a cheap and reliable way of keeping more heat indoors. It won’t work in older houses: consider cladding the outside with insulating material and rendering over it.

Cost? About £500.

Payback time? Two or three years for detached houses.

Woodburning stove

Consider a stove that heats water for central heating. But you may not be allowed to burn wood in clean-air zones in city centres.

Cost: £2,000 to £5,000.

Payback time? Five to 10 years.

Double glazing

Replacing draughty wooden windows is a pricey way of making your home greener.

Cost? About £500 per window.

Payback time? More than 10 years.

Tip: get estimates from local specialists as well as the big firms. They are often cheaper.

Ground-source heat pump

Extracts warmth from the soil for underfloor heating. Makes more financial sense if your house is not on a gas main: it runs on electricity, which is about four times as expensive as gas per kilowatt hour. You need a big garden.

Cost? £6,000 to £12,000 for installation.

Payback time? Probably more than 15 years.

Insulating your door

Consider replacing a wood and glass door with a thick plastic one made to look like wood.

Cost: £250 to £500.

Payback time? More than 10 years.

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