most efficient way to use our Heat Pump

​@Kintyrescott 

Hi and welcome to the forum and an interesting question to start with. Heat pumps work most efficiently when used continuously because you lose efficiency when you start and stop them. My suggestion is just to use it as you wish but if you have changed over from a gas boiler you may find it a bit more expensive.  However, gas prices are going up so you have made a good choice overall. Your solar power will offset the cost of running the heat pump but it's a poor match to heating requirements so selling the spare  energy as SEG will give you the return on that.

Peter

Hello Peter, many thanks for your answer, it helps. However a follow-up question if I may. Typically you would like your house to be cooler overnight, but if we use it continually the house will stay at the warmer temperature (maybe too warm for sleeping), do you have any recommendations?

lile 

As I run a hybrid gas boiler / HP system I'll tag ​@juliamc and ​@BPLightlog to see if they have any recommendations on this. I can program both my systems to change the temperature at their individual thermostats but if you want to change the whole house temperature that may need a different approach.

Generally we have a lower temperature in the bedroom at night so we set a lower temperature at night to allow for that. During the day we are in the lounge and have a higher temperature. It seems to work well but it may be different with just a HP. 

Peter

I have a Daikin heat pump with radiators, the TVRs on all the radiators are fully open. We like a warm house...

I have a schedule set for 22 degC at 3:40am (can’t remember why this time !) and 21 degC at 9pm. That one degree setback is enough to effectively turn off the heating at 9pm and it generally doesn’t come on again at night unless it’s Baltic outside. I don’t change any settings at all so it’s like this winter and summer.

The heating came on this week for the first time since the spring, the outdoor temperature dropped to 10 degC and the indoor temperature must have dropped below 21 to trigger it.

There’s no point in letting the whole house cool down overnight as the heat pump just has to work harder to warm it back up. Having said which, our bedroom radiator is sized to only get the room to 18 degC and we always keep a window open there overnight.

One thing that I have done since getting solar panels is to heat our hot water tank when the solar is at its peak. For us that’s around 11:30am. The system will only heat the radiators or the tank but not both together, so at that time we don’t notice the heating going off for the 45 mins it takes to do the hot water.

You could experiment with dropping your tank temperature one degree per week and see if you notice. We have ours set to reheat when it’s dropped below 30 degC which can happen if I have a long shower (hair wash!). 

Just a word or two of caution here, but with the caveat that I don’t have a heat pump and thus have no personal experience to share:

1. You asked about ‘the most efficient way’ of using the heat pump (HP). Efficiency when considering heating systems usually means the relationship between quantity of energy consumed and amount of heat delivered. For an HP, the common term for efficiency is Coefficient of Performance (COP). The figure is usually in the range 2 - 5, meaning that for each kWh of electricity consumed, the system delivers between 2 and 5 kWh of heat. Compare this to the efficiency of a modern gas boiler, which typically has an efficiency of 90% - equivalent to a COP of 0.9. For each kWh in the gas consumed, 0.9 kWh are delivered as heat, The other 0.1 kWh largely goes up the chimney to keep the sparrows warm. The efficiency of the panel heater in your bedroom or the fan heater in the bathroom is exactly 100% - every kWh of electricity consumed is converted into heat. That’s a COP of 1. 
     
   Depending on what you pay for electricity, higher efficiency doesn’t necessarily mean lower bills.
     
2. What new heat pump owners are probably most interested in is how effective the 
    HP is. This is largely subjective, but it includes considerations of ‘comfort’ - e.g.  indoor temperatures at different times of day: cooler at night, say, or during the day when nobody’s home.  A more effective system may have a lower COP than the maximum attainable, but the difference in cost is not necessarily drastic.
     

There was a really good explanation of ‘the best HP settings’ in a Heat Geek video, but I can’t find it now. Still, there are many informative (if irritatingly garish!) videos in their Youtube channel. Heat Geeks are widely reckoned to be among the best at this sort of stuff, both in this forum and elsewhere.