@info how would you store that heat in a battery? You would need a buffer tank of some kind. I know it's possible, but it would need a tank and heat exchanger.

I have a physical battery that stores electricity so I can fill it at 5p and then use it when the cost would be 15p from the grid. Each kW would be 10p cheaper so my whole battery would be £1.40 a day in saving, plus any solar power which then tops it up.

@batalto

My mistake, I meant electricity, not heat. Have been reading about thermal stores, heat batteries & electricity batteries, will continue to research a bit more in order to understand it all better. 

Hi Info,

As Batalto stated above, and provided that you do not overload your electricity supply, it should be possible to run both an ASHP at an increased load and also charge an electrical battery array, during the 4 hour period when prices are low.

In theory the maximum amount of electrical energy that can be imported from a 100 Amp single phase grid supply is 24kWh, though 20kWh would be a more conservative estimate. Over a 4 hour period it would therefore be possible to import 80kWh of electrical energy.

A 12kW ASHP running continuously at maximum output, with a COP of 2.5, would draw no more than 5kW each hour. So over the 4 hour period would use a maximum of 20kWh of electrical energy. So, again in theory, it would be possible to also charge a battery array of 60kWh capacity during the same 4 hour period, assuming you can afford the initial cost and have room for all those batteries.

I suppose the ideal arrangement would be to increase the temperature setting in all the rooms (except occupied bedrooms) by 2C (or more if possible) during the 4 hour cheaper period, thereby optimising the supply of cheap energy to heat your home. At the same time charging a battery array of say 15kWh capacity. At the end of the 4 hour period, stop charging the batteries and lower the temperature setting back to normal. The initial effect would be that the only heating load would be that required by the occupied bedrooms, which could be provided by powering the ASHP from the charged battery array. As the temperature in the over-heated rooms falls back to the normal setting, the load on the ASHP would gradually increase, thereby draining the batteries at a faster rate. Hopefully the batteries would not be fully discharged before the Sun rises and the outside air temperature begins to increase. The increasing ambient temperature will increase the efficiency of the ASHP, which will mean that less electrical energy is required from the grid supply.

The addition of a solar PV system, of sufficient size, to fully or partially power the ASHP during daylight hours, would further reduce the amount of electrical energy required from the grid.

The above arrangement should reduce the amount of energy drawn from the grid over a full year period and also reduce the total running costs.

@derek-m little more complex than that. Most batteries have a "peak charge" power - mine is 3.2kw, tesla is a little higher at 5kw. This essentially caps the power you could save, unless you have two inverters charging separate batteries. For me my Depth of Discharge (DoD) on the batteries is 80% so I only have 80% capacity available; this is to protect the batteries and extend their lives. so my 14.2kwh capacity is 11.36kwh which means I can fill them to the max in 3.5hrs, more or less perfect for my needs.

On your further view, yes that is my plan. Pump some heat into the house when its cheap 5p @ 2.5COP is 2p a kw (so cheaper than gas) and bring the living spaces, not the bedrooms up to temp - that should then carry over into the day, lowering the overall heat load demand at a higher rate.

I tried to articulate some of my thoughts and concerns I raised in this thread about the rising cost of electricity and the potential effect it will have on our property this winter: https://myhomefarm.co.uk/the-cost-of-sustainability  

Yup I see the issue you have.  I've just locked in at just over 16p; more than the 11.6p/7.6p I had last year. I'm still very glad I have the ASHP rathet than storage heaters.  

There are a lot of all electric households that are going to be hit quite hard by this increase.  Imagine the outcry if gas prices went up 25%. It's worse than that because electricity was already two three times as much as gas.

@kev-m 

Which provider did you just sign up with, Kevin? It sounds like a good deal atm. 

@info, Neon Reef. It may not be available nationwide; you'll have to get a quote and see 

@kev-m 

Thank you, Kevin

@kev-m, cheapest tariff to date for us. 17.5p/kWh on their Neptune V2. I've bookmarked them as a potential switch.

My current tariff expires in September. Presently 13.9p per kWh and struggling to get any new one at less than 20p. The gap between electricity and gas appears to be widening further. It’s the opposite of what's required and effectively undermines any campaign to increase the number of heat pump installations. 

Mike

@mike-patrick, this a massive point of concern for heat pump owners at the moment. We understand that gas tariffs are also going up, which is looking like it’s going to be a heavy financial winter for many in the UK.

I covered our concerns on this matter in a recent post: https://myhomefarm.co.uk/the-cost-of-sustainability  /p>