The GS heatpump uses more electricity than we expected. The Immersion Heater function comes on all too readily if it is not getting enough heat from the ground, and not quickly enough.
The solar earth charging would save more energy than an entire roof could generate with PV. But how about the idea of doing both!?
We used 8500 Kwhr from Aug 08 to Aug 09, and we would like to reduce that. The UK govt. have announced german style Feed-In-tariffs starting next April 2010 which make PhotoVoltaic well worth doing.
Before April, 2010 the grants system is still in place, but after that, we will get 36.5p/hr, 3 times the amount paid for Grid electricity. This is in effect somewhat more because we can use home created electricity direct and dont have to pay the Grid supplier for it. This equation is explained on Solar Century's website.
Therefore, we will also provide Solar Photo voltaic Panels (which will of course power the pump that is moving the glycol down to the soil), but is likely to generate more than 2000 Kwhr per annum for this angle of roof in this location.
The income from the panels could be more than our total annual electricity bill - meaning that we have a negative electricity bill!
For the PV, we are currently working with EvoEnergy, a local agent for Solar Century.