What's the most cost effective way to heat your home with an air source heat pump (ASHP)?

The important thing with a heat pump is running it efficiently. You can have your house at the same temperature but it can cost different amounts, depending how you're running the heat pump... and that's really annoying if you just want a warm house and don't want to be mucking about with the settings.

In general, the lower the temperature the heat pump runs at the more efficient it is. But you also want the water warm enough to heat the house effectively. That means you need the water at different temperatures depending on the outside temperature... this is called weather compensation and is generally the best way to run a heat pump.

Now for overnight heating... if you let your house get too cold overnight the heat pump will have to work harder in the morning to heat it up again. Working harder makes it less efficient so a morning boost could cost you more than running the heat pump at night to stop the temperature dropping so much. It isn't an exact science but it's generally thought that having your overnight house temp 2 or 3 degrees below your daytime temp is about right. We have a daytime temp of 18 or 19, depending on the day, an evening temp of 20 and an overnight temp of 17. It's actually rare that the heat pump will start up overnight because the house will only lose 3 degrees of temp on very cold nights.

Key here is that not every Heat Pump is installed with the same set up. Some have large buffer tanks, others have only small or internal buffer tanks others, like ours, have large heat batteries. Also the emitters / radiators are key. We have Climaventa emitters that are, frankly, useless. Where we have removed them and installed oversized rads the heat emitted is far greater. 

We have tried running ours 20+ hours a day but the cost was way too high. After 4 months we have found most optimal to charge out Electrical Battery storage using off peak energy, then have the heat pump come on at 6:30 - 8:30am. If its a sunny day the house heats itself, if not a small log burner is adequate during the day. 4pm -9pm the thermostat is set on 21.4 degrees and that just about keeps the house warm with the log burner doing the rest in the lounge. 

If it’s a sub zero night we will also run the Heat Pump for a couple of hours. 

Key here is to remember we have the Sunamp Heat Batteries which means our system can heat without needing the Heat Pump for a period of time. When the heat batteries are exhausted the heat pump is used. When not heating the Heat Batteries ‘trickle charge’ from the Heat Pump. 

Zoning is also working great, we only have it our bedroom at the moment but when that reaches temp the wifi TRVs shut the 2 x large rads off freeing up heat capacity on the rest of the system. 

Sooner Climeventa emitters are gone the better

Yes, @Jess_OVO , the heat pump will remain off when it doesn't need to provide heat on summer days. How it does this depends on the controls. I believe that some are able to monitor temperatures over a 24 period so won't switch on at all if the average temperature is high. Others will come on if you have a particularly chilly morning.

I use a heat pump to heat my greenhouse. So I don't even know how to heat my house with it. I have electric heating in our house. My husband and I finally renovated our house and we have solar panel electricity. The new radiators work from that. *Edited by a moderator*. I have a hard time imagining a heat pump inside the house.