Energy myth-busting: Is it cheaper to have heating on all day?

clive764

Contrary to the MSE Article there is a definitive answer if you have an Air Source Heat Pump system it is ON 24/7 365 days a year. It is controlled by 6 thermostats in 6 "Heat Zones" in my house. It is therfore important to set each thermostats acurately.

QrizB

clive764 said:

Contrary to the MSE Article there is a definitive answer if you have an Air Source Heat Pump system it is ON 24/7 365 days a year. It is controlled by 6 thermostats in 6 "Heat Zones" in my house. It is therfore important to set each thermostats acurately.

You're not the first MSEer to claim this.

I do however struggle with the idea that, while we encourage everyone to switch off all their other electrical appliances when they're not in use, there's something magical about heat pumps that means switching them off doesn't save electricity.

If your heat pump only uses 1 watt when idle, over the six summer months that's 4kWh.

Reed_Richards

QrizB said:

clive764 said:

Contrary to the MSE Article there is a definitive answer if you have an Air Source Heat Pump system it is ON 24/7 365 days a year. It is controlled by 6 thermostats in 6 "Heat Zones" in my house. It is therfore important to set each thermostats acurately.

You're not the first MSEer to claim this.

I do however struggle with the idea that, while we encourage everyone to switch off all their other electrical appliances when they're not in use, there's something magical about heat pumps that means switching them off doesn't save electricity.

If your heat pump only uses 1 watt when idle, over the six summer months that's 4kWh.

I can't speak for @Clive764 and I don't follow the point he is making but my heat pump still supplies hot water in the summer and there are very few months when we don't need some heating some of the time.  When I last looked, my heat pump used about 10 W when idle.

orrery

bilbomacuser said:

One thing missing from the article is the fact that a high proportion of condensing boilers have been poorly installed and / or use controls that don't allow the boiler to condense.  For example even controllers that appear to be modern such as Hive, actually act like old fashioned 'on-off' thermostats and don't allow condensing boilers to work efficiently.

True. Controllers that use proportional control (turning the boiler on and off in proportion to the heat required) will do the job admirably, and in most cases will be streets ahead of just turning the return temperature (and effectively the flow temperature) down.

Many boilers will start to misbehave with a low flow/return temperature. Once the boiler reaches the maximum set, it will back off the burner power until it reaches the minimum possible power and then both the return and flow temperature will increase until the boiler shuts down (all depending on the conditions at the time) - unless the boiler power is perfectly matched to the situation, which is most unlikely to be true in all situations and seasons.

A good controller with proportional control will shut the boiler down, for the appropriate period, and start up afresh with the return and flow temperatures rising until it shuts down again. This ensures that it spends the maximum amount of time in condensing mode, unless the temperature is way below the set temperature, when it has the flexibility to just run at 100% (effectively moving out of condensing mode) when the heat is required most. This control strategy will work in all seasons.

clive764

Reed_Richards said:

QrizB said:

clive764 said:

Contrary to the MSE Article there is a definitive answer if you have an Air Source Heat Pump system it is ON 24/7 365 days a year. It is controlled by 6 thermostats in 6 "Heat Zones" in my house. It is therfore important to set each thermostats acurately.

You're not the first MSEer to claim this.

I do however struggle with the idea that, while we encourage everyone to switch off all their other electrical appliances when they're not in use, there's something magical about heat pumps that means switching them off doesn't save electricity.

If your heat pump only uses 1 watt when idle, over the six summer months that's 4kWh.

I can't speak for @Clive764 and I don't follow the point he is making but my heat pump still supplies hot water in the summer and there are very few months when we don't need some heating some of the time.  When I last looked, my heat pump used about 10 W when idle.

It is quite simple @Reed_Richards the Air Source Heat Pump is "ON" 24/7 365 days a year. The 6 zone Theromostats are set at 18-19 degrees and the hot water programmed at 48 degrees. The underfloor heating downstairs and the radiators upstairs are only activated when the theromostats fall below 18-19 degrees, and the water is heated when the tank falls below 48 degrees, mainly when water is drawn from the tank when having a shower etc and the tank is replenished. So constant hot water.

Reed_Richards

@clive764, I don't really see how this contributes to the debate.  Your ASHP is "on" all the time but only actually operates when at least one of 7 thermostats (6 zones, one hot water) calls for heat.  Fine.  Is this the most economical way to heat your house?  You seem to think so, but provide no evidence to support this assertion.

Qyburn

Irrespective of the type of heating system, a house loses more heat if heated 24/7 than if it was allowed to cool in between occupancy periods. So needs more heat supplied over any given time period. Whether that "more" is a significant amount will depend on inside/outside temperature difference and on how effectively the house is insulated.

Reed_Richards

I hope nobody would dispute that, @Qyburn.  But what has kept this thread running and running is the suggestion that because of the way some heat sources operate, the extra energy used to bring the house back up to temperature is more than the energy saved in allowing it to cool.  Gas boilers and heat pumps tend to work less efficiently when working harder so this is indeed a theoretical possibility, and there is a paucity of actual evidence one way or the other.

JSHarris

Our heating is effectively on 24/7, as the ASHP heats the concrete ground floor slab, that has embedded UFH pipes.  However, heat only "charges" the floor overnight, during the cheap rate period, so the question is then "What counts as having the heating on all day?".

If "all day" is defined as always supplying heat to the house, then that is exactly what our heating does.  If it is defined as the time that the heating system is drawing power then this doesn't meet the "all day" definition.

FWIW, this system is fairly cheap to run, I think.  Our house isn't that small (it's about 1,400 square feet, with a ground floor footprint of 807 square feet) and our only "fuel" is electricity (no gas, oil or solid fuels).  Our electricity bill, including running my car (an EV) for this year will be around £750.  Heating and hot water account for between £200 and £250 of the annual total.  Our last house, a bungalow that was about half the size of our current house, with a gas combi for heating and hot water, cost about £1,200 in gas the last year we were there (2016).

coey

Don't believe in thermostats , only got one as legally obliged to. Use timer [ 8.30-10.30 / 16.30-22.30 ] plus manual interventions as required. central thermostat fitted in hall and set to 25 [ which it will never reach nor do i want it to reach ] ALL rooms fitted with Thermostatic radiator valves which control desired temperature in each individual room ONLY when that particular room needs heating......Can't believe TRV's have not been mentioned more , in my opinion mandatory fitting of TRV's should come way before any ridiculous ideas like heat pumps.