 It is more productive to capture energy with Solar Thermal Technology that it is to do it with Photovoltaics. Efficiency is expected to be anything up to 60% by 2020. However, these panels are physically more bulky and remember, there is fluid flowing through them. They are part of systems that have to tap into a house's hot water system. It can require some plumbing and some moving parts. Hence it can be a bit more complicated that Solar Electric - even if it is far cheaper to install for the energy you get out. For example £13k might get you 2500kWh/yr with PV but you can get the same in hot water for £5000 worth of Solar Thermal panels.
So far 100,000 homes in the UK already has this technology installed. Older styles only consisted of a flat metal plate but the new technology uses a set of vacuum tubes as is illustrated on this page (above and below). The industry pundits still argue the pros and cons of evacuated tube versus flat panels! You will hear every opinion. These systems do not replace your Heating System but can supply most of your Hot Water needs during the Summer Months but very little in Winter. Be cautious of the sales brochures offering up to 70% savings on your hot water bill. Only six months of the year would supply enough energy to avoid using the conventional boiler. The panels can heat the water from 10 degrees Celsius up to 60 degrees Celsius or more. Some heat can be lost back into the environment if hot water is pumped from the hot tank back to the roof when it is cold outside however, modern controller systems prevent this.  Cash savings per year vary from £23 for a small house up to £94 for a large home. Since a larger home's installation costs only 16% more than the small one this means that the pay back is far better on the larger installs. Likewise the costs per tonne of CO2 averted is £170 GBP for the larger install versus £600 GBP for the smaller. The most efficient evacuated tube solar collectors convert 70% of the energy falling upon it into heat. However the installation must face south (obviously in the northern hemisphere) and be tilted up by about 30 degrees (in the UK). Anything else will not receive the full amount of energy possible. Typical installations are between 2 and 4 square meters supplying 1680 to 3360kWh/year.
 In June this latter figure could supply 545 litres of hot water. We consume 50 litres per person per day. A Bath needs 80 litres whilst a shower only 30 litres. This is quite a lot of capacity but it would be a lot less with pumped showers.
Hence the amount of fossil fuel you save depends upon how much hot water you use and what time of year it is. A greedy household could save only 40% whilst the most frugal may save 90%. When the Energy and Climate Change Secretary Ed Miliband announced the feed-in tariff (FITs) levels on February 1st 2010 his department also published a blueprint for a similar scheme to be introduced in April 2011 to incentivise low carbon heating technologies. The renewable heat incentive (RHI) will be a world first. The FIT & RHI schemes are designed to bring about a significant increase in the amount of locally produced green energy, as a contribution to the wider shift of the energy mix to low carbon. The Department of Energy and Climate Change RHI scheme is to incentivise renewable heat generation at all scales. This will guarantee payments for those who install technologies such as ground source heat pumps, biomass boilers and air source heat pumps. Under the proposed tariffs the installation of a ground source heat pump in an average semi-detached house with adequate insulation levels could be rewarded with £1,000 a year and lead to savings of £200 per year if used instead of heating oil. The heat incentive could help thousands of consumers who are off the gas network lower their fuel bills and gain a cash reward for greening their heating supply. Details of funding for the scheme were meant to be published in the Budget 2010 however the UK's new coalition Government was quiet about the matter leading to an Early Day Motion being raised askng them to recommit to the RHI. The signs are still good but watch this space for new announcements. The money comes from a levy administered by the official regulator Ofgem on sales of fossil heating fuels and is collected by the suppliers of these fuels. Therefore if you install a renewable energy system you get a double benefit: a) Your income from the Renewable Heat Incentive b) Because you are producing some of your own heat, you will buy less gas or fuel and therefore pay less for it (and so less levy) There are a couple of good web sites you can check out if you wish for further information. These are: - www.rhincentive.co.uk - www.ownergy.co.uk | 
