Hi,
We built a 190m2 ICF house with triple glazing, 300mm eps underfloor, 600+mm insulation in loft, MVHR
Our house is all electric but we do have a wood burning stove.
Our heating and hotwater come from E7, heating by direct imersion a 500L thermal store, wet underfloor heating downstairs. No heating upstairs.
Total electricity demand in the last 12 months has been 7200 kWHr. E7 overnight useage = 3800 kWHr, if you assume that the background load for all the usual bits and bobs is 250w, then the energy to provide heating and hot water is around 3100kWHr/year. 1 kWHr of E7 electricity costs around 7.2p, therefore we provide heating and hot water for about £230/yr.
If we did it all with an ASHP @ a COP of 4, then this bill would drop to around £60/yr.
This means an ASHP would save about £170/yr - and that assumes no breakdowns or maintenance.
By the time an ASHP has paid itself back, it is in the scrap bin and you need to buy a new one.
Stick to an imersion heater, much cheaper in the short term, long term, and less to go wrong.
