A great article on Energie Solar Thermodynamic Hot Water – Comparing Running Costs.
Also look at this post about how they see the systems working, being installed etc.
Looking at the The Energie ECO 200is:
on a really good day (sunny and warm) it will supply at most 4.55 kW of energy and will consume 595W. On a bad day (cold night) it will supply 2.8 kW and consume 890 W – so the coefficient of performance would vary from 3.14 to 7.64 – so for every unit (kWh) of electricity you consume you would return between 3.14 and 7.64 kWh of heat for hot water.
As of February 2012 average gas prices were 4.1p per kWh and electricity averaged 13.7p per kWh. Gas (and oil) boilers have a small level of inefficiency (at best they are 90% efficient over the year) and thus the cost per kWh of “heat to the water” would be 4.56p. With the Energie system the cost would average at 2.54p (13.7p divided by 5.39).
Annual running cost per kWh:
– Energie 200is, £0.28
– Gas boiler, £0.51
– Oil boiler, £0.77