Power consumption heat pump

Reed_Richards

Cardew said:

Both the old Energy Saving Trust trials of scores of ASHPs and GSHPs gave case studies of various installations. On the retrial(the first set of results were appaling) manufacturers were called it to redesign the installations and some used large triple panel convectors to enable the water temperature to be in the range 35 -40C.  iirc a couple used skirting radiators panels.

I had my heat pump installed in mid December 2020.  As of 13th October (i.e. after 10 months) my average electricity consumption by the heat pump was 18.55 kWh per day.  With oil my average energy consumption was 54.6 kW h per day.  It's impossible to make exact comparisons because some years are warmer than others and I did not have the oil boiler long.  But I don't seem to be doing so badly so I can only assume manufacturers and installers learned lessons from the case studies you refer to that were put into practise by the time my heat pump was installed.

[Deleted User]

Is there a nice little graph somewhere that displays ASHP v GSHP electricity required at various outdoor temperatures to bring a room up to 21 degrees?

Thanks.

[Deleted User]

Reed_Richards said:

Cardew said:

Both the old Energy Saving Trust trials of scores of ASHPs and GSHPs gave case studies of various installations. On the retrial(the first set of results were appaling) manufacturers were called it to redesign the installations and some used large triple panel convectors to enable the water temperature to be in the range 35 -40C.  iirc a couple used skirting radiators panels.

I had my heat pump installed in mid December 2020.  As of 13th October (i.e. after 10 months) my average electricity consumption by the heat pump was 18.55 kWh per day.  With oil my average energy consumption was 54.6 kW h per day.  It's impossible to make exact comparisons because some years are warmer than others and I did not have the oil boiler long.  But I don't seem to be doing so badly so I can only assume manufacturers and installers learned lessons from the case studies you refer to that were put into practise by the time my heat pump was installed.

My average electrical consumption per day is 3KWh
And gas is 5KWh - we have full GCH
We live in a 3 bed semi and are never cold

wittynamegoeshere

It's important to point out that a heat pump doesn't have a flue.  I know gas and oil boilers are pretty good these days, but they still spray some of the heat out of the flue, so you never get the same amount out that went in.  I saw a gas fire recently, a current model, its energy certificate said it was 50% efficient and I don't think this was unusual.  It's probably worse than that when you consider that it will be pulling cold air into the room elsewhere to feed the warm air that it's shoving out of the chimney.

QrizB

Swipe said:

Verdigris said:

Deleted_User said:

All of this extra electricity needed to power the heat pumps has to come from somewhere
Together with all of the extra power needed for EV's
Where exactly is the power coming from?
Remember that solar panels are not at their most efficient in winter 

Do you not listen to the news? Wind generating capacity is going to be increased to 40GW. Guess which season the wind blows hardest in...

Don't forget they have to be halted in strong winds

Most of the big boys will still generate in 60mph winds.

The Vestas 4MW turbine, which is mid-sized, won't vut out until 25m/s (56mph).

QrizB

DeletedUser said:

Is there a nice little graph somewhere that displays ASHP v GSHP electricity required at various outdoor temperatures to bring a room up to 21 degrees?

No, there are far too many variables. That's why a heat pump quote needs to start with a proper energy survey (not just the tick-box exercise of a EPC).

QrizB

wittynamegoeshere said:

It's important to point out that a heat pump doesn't have a flue.  I know gas and oil boilers are pretty good these days, but they still spray some of the heat out of the flue, so you never get the same amount out that went in.  I saw a gas fire recently, a current model, its energy certificate said it was 50% efficient and I don't think this was unusual.  It's probably worse than that when you consider that it will be pulling cold air into the room elsewhere to feed the warm air that it's shoving out of the chimney.

Boilers, of course, draw their combustion air from outdoors so you don't get the loss of heated air like you would with an open fire. Hence the typical boiler claim of 90% efficient.

wittynamegoeshere

QrizB said:

wittynamegoeshere said:

It's important to point out that a heat pump doesn't have a flue.  I know gas and oil boilers are pretty good these days, but they still spray some of the heat out of the flue, so you never get the same amount out that went in.  I saw a gas fire recently, a current model, its energy certificate said it was 50% efficient and I don't think this was unusual.  It's probably worse than that when you consider that it will be pulling cold air into the room elsewhere to feed the warm air that it's shoving out of the chimney.

Boilers, of course, draw their combustion air from outdoors so you don't get the loss of heated air like you would with an open fire. Hence the typical boiler claim of 90% efficient.

For a balanced flue, I'm wondering if the figures may be a little dodgy.  If it's cold outside then the incoming air is much colder than the return water in the heating system.  So the heating is starting from below the temperature that say an electric heater element would be starting from.  If you were to cut the gas off but leave the pump and fans running then it would actively cool the house by circulating chilled water.

I wonder whether this is considered in comparing efficiency figures, I think it probably isn't, those 90+% efficiency figures that are quoted are probably only achieved when the outside air is warm, i.e. when you won't be using the heating.

Also I don't think these figures include the electricity used by the pumps and fans.

Verdigris

I wonder whether this is considered in comparing efficiency figures, I think it probably isn't, those 90+% efficiency figures that are quoted are probably only achieved when the outside air is warm, i.e. when you won't be using the heating.

The 90%+ efficiency is achieved when the system first fires up when the circulating water is cold. That's why it is important to properly balance the system and have thermostatic radiator valves, so as much heat is dissipated into the rooms and the return water is a cool as possible.

wittynamegoeshere

You're talking about the temperature of the water.  I'm referring to the chilled outside air that's continually pumped through the heat exchanger, which I don't think is included in the calculations.