Renewable technologies remain (2011) expensive to install but can be cheaper over the long term.
- Solar thermal technology: Harnesses the sun's power to create heating and hot water. In the UK, where the sun is not so strong, it is less effective in terms of heating space but can provide up to 60% of a household's hot water needs.
- Solar energy: Photovoltaic panels generate electricity. They harness light but don't need direct sunlight, though this is more efficient. (They can actually lose efficiency if they get too hot - e.g. in the south of Spain). Excess energy can be fed into the National Grid. Energy companies are offering to rent your roof area to install these panels.
- Air source heat pumps: Take heat from the air (even when it is minus 3 degrees outside) to boil refrigerant and then compress the gas that is formed, creating heat. To cool the house down, the process can be reversed, so the refrigerant absorbs heat inside the house and the pump pushes it outside. Heat pumps use electricity to run their gas compressors but as their efficiency has increased, now a heat pump might give out 4kW of heat for every 1kW of electricity used, making it 400% efficient. But if you already have a condensing boiler, you should not rip this out and install a heat pump instead as you would not see any savings. Air source heat pumps are easy to fit onto existing systems. (2011: Start at around £700.)
- Ground source heat pumps: Take heat from the ground. They need either ground collectors or bore holes, which is likely to make installation cost prohibitive for homeowners and small businesses. Cost is less of a factor for new builds where drainage work is also required.
Other ways of cutting energy
- Insulation: Around half the heat loss in a typical house is through the walls and the loft. Recommended depth of loft insulation is 270mm (2011). For houses with solid walls, there is now a special 10mm thick wallpaper that reduces heat loss by around 30%.
- Boilers: Band G (lowest efficiency) are typically over 15 years old and 60% to 70% efficient. Band A condensing boilers are at least 90% efficient.
2011: Eco supplement,
Daily Telegraph
