GarethC wrote: ↑Thu Nov 16, 2023 1:34 pm
...how costly and feasible would it be, in principle, if you'd installed circa 100kWh of home battery and gone all electric, instead of having storage heaters and hot water storage? Would there be a simplicity advantage?
Very feasible!
However you don't need a 100kWh battery but you do need a heat pump.
According to Ofgem a typical house in the UK uses 2700kWh of electricity and 11500kWh of gas per year.
Now usage isn't spread evenly over the year, you will use more electricity and almost all of your gas in winter. A gas boiler is also c. 75% efficient (at best).
So on to the maths: For a typical winter day I'm going to assume you use 60kWh of gas and 10kWh of electricity per day. The gas produces 45kWh of heat at 75% efficiency which would require 15kWh of electricity with a CoP of 3. So your total electricity consumption would be 25kWh per day.
How big a battery you need depends how much of your usage you can shift into the cheap period (washing machine/dishwasher etc) but a 20kWh battery should be plenty.
You can implement the HP however you like. A2A (air to air) is simplest and 2x "2.5kW" units are probably the right size because they can run for a few hours a day in the shoulder months, can easily run at 50% capacity (a typical A2A is happy running down to 25% of it's nameplate capacity) when operating at their design power and can run ad 2x the design power to heat a cold house or in very cold conditions also 2x heat sources will make for a more-even heat spread across your house. Alternatively you can plumb a 5kW (air-to-water) ASHP into radiators. but that solution is usually only implemented in situations where a wet system already exists and it sounds like it doesn't in your case but it could possibly be a better choice if your house has a complex layout with lots of small rooms. .