How to install renewable technology in your home

Similarly, pressure groups like the Existing Homes Alliance are suggesting that homeowners whose properties score low marks on their Energy Performance Certificates (grades F and G) will be legally prevented from selling until they raise their scores. While most scores can be raised by improving energy efficiency, installing solar panels or having renewable sources of heating will also help raise a home's EPC score.

The good news is that with increasing demand for big-ticket items such as solar panels, the price is coming down; builders, who a few years ago would not have known what a ground source heat pump was, are now familiar with these new technologies and with the Government now embracing the idea of a Feed In Tarriff, the payback time for electricity-producing features will now be more than halved.

So, what are renewable technologies and how easy are they to install? There are five basic renewable sources of energy, most or all of which can be harnessed, depending where you live, for heating and lighting your home.

These are:

• Solar: heat from the sun (solar thermal) can heat your water via roof top collectors; light from the sun (photovoltaics) can be transformed into electricity.
• Wind: Turbines transform wind energy into electricity.
• Air source/ground source: Using compressor technology working the opposite way to fridges, air source and ground source heat pumps take heat out of the air or soil to heat water tanks and radiators.
• Wood: wood is a renewable energy source as it re-grows. It is also carbon neutral as the CO2 it produces when burnt is cancelled out by the CO2 the living tree absorbed as it grew.
• Hydro: We have yet to tap even a minute fraction of the water power in this country. People living on rivers are starting to use water wheels or turbines to produce electricity for their homes.

Solar

Solar Thermal collectors work best during the spring and summer months and can supply between 50 and 70 per cent of a family's hot water needs. Collectors work best when mounted on south-facing roofs, to gain maximum benefit from the sun. There are two basic types of solar thermal collectors: flat plate collectors and evacuated tube collectors. But both do roughly the same job: they absorb the heat from the sun through a glass surface and into water-filled pipes. This heat is then transferred to the water in domestic hot water tanks.

Over the years the efficiency of these solar thermal collectors has been steadily increasing, with better materials and better methods of heat transfer, and their image has transformed from a haphazard and unreliable technology for super-greens to a hi-tech, integrated system providing reliable hot water for most of the year.

Cost: A 4 metre square flat plate system costs around £3500; this would raise the temperature of 33,000 litres of water from 10 degrees to 65 degrees, providing hot water roughly from March to October.

Grants: Under the Low Carbon Buildings Programme (LCBP) grants of up to £400 are available.

Savings: Depending on water use, between £100 and £300 a year.

Con: To make maximum use of heat gathered in the day, for night-time baths and early morning showers you should have a tank capable of holding at least 180 litres, preferably 300 litres for a family: this is probably far bigger than your present tank, the average hot water tank being 160 litres.

Photovoltaic (pv) panels use silicon crystals to generate electricity from sunlight. Panels are lightweight and can be fitted even on flat roofs (mounted at an angle to get maximum benefit). Although this technology is expensive, it is seen by many countries as the best way to produce renewable electricity: Germany has invested in a massive programme of installing panels on domestic homes and its pv industry now provides jobs for more than a quarter of a million people. Spain is installing large-scale pv collectors in its central plain, making use of the brilliant sunshine it receives.

The cost of silicon is expected to come down over the next year as more sources come on stream and this, combined with the proposed Feed in Tarrif - where home owners are paid a premium rate at three to four times that of ‘brown' electricity for the energy they produce - will at last make pv a reasonable proposition for home owners even with modest budgets.

Cost: To supply an energy-efficient house (with eco bulbs, standby controls and energy-watchful occupants) with all its electrical needs (about 2.5 mWh a year), an outlay of £9000 - £12000 is needed.

Grants: Up to £2,500 under LCBP.

Savings: Depending on how many panels are installed, the entire electricity bill could be paid for; many homeowners who install the maximum amount of panels report actually making money as well - £50 - £100 a year from their electricity supplier, for the excess they sell back to the grid.

Con: Still a very expensive option for many.

Wind

Wind: While much was made of David Cameron's ‘green' credentials when he installed a roof-mounted wind turbine on his London home, the efficiency of these small scale turbines is now in question. It is now fairly well accepted that for a wind turbine to be of any use it needs to be pole-mounted, away from the house (which creates turbulence which disrupts the action of the turbines). In addition there is a sharp loss of energy when the DC current the turbine produces is converted into AC current that a building uses.

However, if you live on exposed land in a rural area and have a large garden or paddock, then a 15 metre-high turbine could helpfully add to your renewable energy supplies. Wind turbines can help during the winter, when winds are stronger, and when solar technology is at its weakest.

Cost: £22,000 - £26,000 will buy you a 12 - 15 metre high pole-mounted turbine, including installation costs.

Grants: Up to £2,500 under LCBP.

Savings: A 12 metre high turbine with two metre diameter blades could generate between one third and one half of a home's electricity needs as long as average wind speeds are above 27 miles per hour.

Con: Unlike solar panels, pole mounted wind turbines still require planning permission and your neighbours might not like it.

Air Source/Ground Source

Heat pumps use the same technology as a domestic refrigerator, but in reverse: heat is taken either from the air, or the ground via pipes filled with a mixture of water and anti freeze; this is then passed through a unit which compresses the liquid, which raises its temperature. Air source heat pumps can work down to outside temperatures as low as -6 degrees and are useful when people have small gardens as ground source heat pumps require coils of piping (about 80 metres) being buried at about 1 metre's depth under the garden. This obviously requires much disruption to the garden and is generally undertaken alongside other building work such as an extension or re-landscaping the garden. An alternative for small gardens is a vertical borehole going straight down which is then filled with pipes; this is more expensive.

A home with heat pumps requires more electricity to run the compressor unit but the efficiency justifies the extra electricity needed. For air source heat pumps, for every one unit of electrical energy, three units of heat are produced. In ground source heat pumps, the efficiency is higher: about 1:4. Many homeowners choose to install pv panels at the same time as installing heat pumps so the extra electricity used is offset by the panels.

Cost: Around £7000 for an air source heat pump complete with new hot water tank and radiators. Between £8000 - £12000 for a ground source heat pump including all additional plumbing.

Grants: £900 for an air source heat pump; £1200 for ground source.

Savings: Depending on the size of the system you could save from £400 a year for replacing a gas central heating system (£1000 a year for an oil-fired one) up to wiping out your entire hot water and central heating bill.

Con: You'll need space for the compressor unit (about the size of a large fridge); you may need to replace your radiators.

Wood

Wood has been used to heat our homes for millennia and is now making a comeback in its posh new green form called biomass. The easiest way to add wood to your energy mix at home is to open up that old fireplace, get the chimney swept and install a super-efficient wood-burning stove; you can even get ones with enough space on top to heat a pan of water; larger versions also include ‘back boilers' to heat your water and a number of radiators. The next step up is a wood pellet stove, which is much more efficient in terms of energy produced (4700 kWh/tonne compared to 3900 kWh/tonne for seasoned logs). But you can't beat the beauty of a wood burning stove on a cold winter's night.

Cost: £1000 - £5000 depending on size, function and fuel type.

Grant: £600 for a wood pellet stove.

Savings: It depends on the size of your home and how hardy you are, but even a single wood burner in the main living room of a home can delay turning the heating on by several weeks in the Autumn, saving you £100 - £200.

Con: You have to clear out the ash on a regular basis, although the roses will love it. You'll need somewhere dry to store your logs.

Hydro

Hydro: There are an estimated 20,000 private water mill sites in the country, of which only a few dozen have installed turbine generators. These can be converted to provide a home's entire electrical needs. For more information visit the British Hydropower Association website.