Can solar also heat my house as well?
We are not convinced this is a good option in Britain. Partly due to the many cloudy days in winter, the average solar energy in a December day is a tenth of that on an average July day. Whereas you need hot water all year round, most people only heat their houses from around October to April. To give any substantial contribution to heating the house in winter the solar array would have to be very large – and then a vast amount of excess heat would have to be dissipated in summer, when you want to be kept cool not hot. We think a far better option is to invest in insulation and to ensure your boiler is as efficient as possible. And if you can heat your house by one or more wood-burning stoves, that can be the most environmentally friendly option of all. Nevertheless we will keep developments in this field under review.

Will your systems work with air source and ground source heat pumps?
Yes, they combine well together, since geothermal systems are much more efficient when heating water to 35-40ºC, the temperature used for underfloor heating, than when heating up to the 65ºC needed for the hot water. And remember even then, some 25-30% of the energy still has to come from electricity

How much electricity does your system use?
Very little. The pump is rated at about 30 watts, a third of a light bulb, and is only on when the solar collector is hotter than the water in the cylinder. We do not have exact figures for the controller but believe their energy use is very low too. We can install systems that do not need mains electricity; these are powered by a small photovoltaic solar panel, but this is a less good option and so is not recommended if grid electricity is available and reliable.

What happens if there is a power cut?
The system can cope with this. If it is dark or the sun is not shining, there is no problem at all. If the sun is shining bright, then soon after the pump stops, the water in the collector will boil. The volume increases, and is taken up by the large expansion vessel included in the solar circuit. In fact the volume of water in the collector at any time is small. The steam remains in the collector, not moving round the circuit, until nightfall when it condenses back to water. The system then rights itself without user intervention and, if the power has been restored, starts again as normal the next morning. If this happens occasionally, it is not a problem, if it happens regularly, then the antifreeze may start to congeal and should be replaced.

Could the water get too hot in summer?
Yes, especially on long periods in summer of full sun and if no water is being used. To prevent scalding, we can install a Themostatic Mixing (or Blending) Valve at the outlet of the hot water cylinder. If the water is above a pre-set maximum, usually 60ºC, cold water is mixed in to bring the water coming out of the taps down to that temperature. We use larger valves than most other installers to prevent any slowing down of the water supply.