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

clive764

The Discussion Thread is not applicable to Air Source Heat Pumps. I have recently moved to a new build well insulated house with an Air Source Heat Pump. The Heat Pump is on all the time and it is controlled with 5 theromostats around the house which turns the heating on/off when the temperature is reached, or drops, in each zone. The water is set to a pre-determined temperature and only comes on when the water temperature in the tank drops below tolerance.

ariarnia

first please can we agree what we mean by 'heat on all day'? 

having a boiler or heat pump running all day costs more than having a boiler or heat pump turned off all day. i don't think anyone disputes that. heating costs more than no heating. 

the question should really be does having a comfortable level of heat maintained by a thermostat all day (complication. set to a higher level during waking hours and lower during sleeping hours)

cost more than

turning the heating on and off so the home is at a comfortable level of heat when someone is home (complication. setting the heating to come on before someone is home so by the time they are home the house is at the required temp). 

clive764

ariarnia said:

first please can we agree what we mean by 'heat on all day'? 

having a boiler or heat pump running all day costs more than having a boiler or heat pump turned off all day. i don't think anyone disputes that. heating costs more than no heating. 

the question should really be does having a comfortable level of heat maintained by a thermostat all day (complication. set to a higher level during waking hours and lower during sleeping hours)

cost more than

turning the heating on and off so the home is at a comfortable level of heat when someone is home (complication. setting the heating to come on before someone is home so by the time they are home the house is at the required temp). 

You obviously did not read my comment properly or you have no knowledge of Air Source Heat Pumps. Unless you are going away for a few days/weeks/months you do NOT turn off the Heat Pump. I received a personal tutorial from the Air Source Heat Pump manufacturer/installer and it is more efficient to have the Heat Pump on all the time (unless being away from the house for a prolonged period of time).

Astria

clive764 said:

ariarnia said:

first please can we agree what we mean by 'heat on all day'? 

having a boiler or heat pump running all day costs more than having a boiler or heat pump turned off all day. i don't think anyone disputes that. heating costs more than no heating. 

the question should really be does having a comfortable level of heat maintained by a thermostat all day (complication. set to a higher level during waking hours and lower during sleeping hours)

cost more than

turning the heating on and off so the home is at a comfortable level of heat when someone is home (complication. setting the heating to come on before someone is home so by the time they are home the house is at the required temp). 

You obviously did not read my comment properly or you have no knowledge of Air Source Heat Pumps. Unless you are going away for a few days/weeks/months you do NOT turn off the Heat Pump. I received a personal tutorial from the Air Source Heat Pump manufacturer/installer and it is more efficient to have the Heat Pump on all the time (unless being away from the house for a prolonged period of time).

This is typically only because of the low running temperature of heat pumps, which typically run at just under 40c will take an absolute age to warm up the property if you switch it off for extended periods, so you should always leave them switched on so they can manage demand themselves. It doesn't change the fact that if you have your thermostat at 30c it's going to cost more than having it at 20c.

ariarnia

clive764 said:

ariarnia said:

first please can we agree what we mean by 'heat on all day'? 

having a boiler or heat pump running all day costs more than having a boiler or heat pump turned off all day. i don't think anyone disputes that. heating costs more than no heating. 

the question should really be does having a comfortable level of heat maintained by a thermostat all day (complication. set to a higher level during waking hours and lower during sleeping hours)

cost more than

turning the heating on and off so the home is at a comfortable level of heat when someone is home (complication. setting the heating to come on before someone is home so by the time they are home the house is at the required temp). 

You obviously did not read my comment properly or you have no knowledge of Air Source Heat Pumps. Unless you are going away for a few days/weeks/months you do NOT turn off the Heat Pump. I received a personal tutorial from the Air Source Heat Pump manufacturer/installer and it is more efficient to have the Heat Pump on all the time (unless being away from the house for a prolonged period of time).

i read your title and know how these discussions go. 

i also know more than one person who does turn there heat pump off for a lot of the year because of the vampire drain of there system.

one in specific i'm thinking of only has the system on for a few months of the year in winter and even then turn it off and go for alternative heating (wood burning stove and heated throw) when theres a few days of fairly mild weather forecast. 

Reed_Richards

I have an air source heat pump and radiators.  I set back the night time temperature by about 3 degrees which has the effect of causing the heat pump not to run overnight unless it is very cold outside.  This makes for good efficiency of operation because it is coldest outside overnight and the heat pump runs less efficiently when it is colder outside.  During the day I gradually ramp up the set temperature so it is warmest in the evening when I am most sedentary.  The house is occupied during the day.

If I had underfloor heating I would behave differently because UFH responds much more slowly to changes in the water temperature.  People often confuse the slow response time of UFH and think that is to do with the heat pump; it's not.   

clive764

Reed_Richards said:

I have an air source heat pump and radiators.  I set back the night time temperature by about 3 degrees which has the effect of causing the heat pump not to run overnight unless it is very cold outside.  This makes for good efficiency of operation because it is coldest outside overnight and the heat pump runs less efficiently when it is colder outside.  During the day I gradually ramp up the set temperature so it is warmest in the evening when I am most sedentary.  The house is occupied during the day.

If I had underfloor heating I would behave differently because UFH responds much more slowly to changes in the water temperature.  People often confuse the slow response time of UFH and think that is to do with the heat pump; it's not.   

Yes, exactly. I have underfloor heating downstairs and radiators upstairs. It is good to have your perspective. I am experimenting on settings and find with hot air rising the ground floor underfloor heat rises to the first floor giving an ambient temperature of around 20-21 degrees without the radiators getting warm.

Qyburn

Aside from heat pumps this myth has been around ever since people had the simplest time clock and the answer is always "no".  There is some slight confusion with commercial buildings where a higher set back temperature has to be used because otherwise the heating can't get the building up to temperature in time.  One local example where a school ran out of oil over Christmas holidays, and it took four days before they could open.

ariarnia

Qyburn said:

Aside from heat pumps this myth has been around ever since people had the simplest time clock and the answer is always "no".  There is some slight confusion with commercial buildings where a higher set back temperature has to be used because otherwise the heating can't get the building up to temperature in time.  One local example where a school ran out of oil over Christmas holidays, and it took four days before they could open.

i dont think its always no. i think it depends on the house. how often someone is home. the 'comfort' temp. the efficiency of the boiler and flow temp (so how quickly it can get the house to temp). 

for us someone is almost always in the house so the the thermostat works and turning on and off to maintain the temp it wouldn't be any cheaper. and our house is old with thick walls so if we go away and leave the heating off in winter it can take a couple of days before the house feels warm again and the damp is chased out. not just the air in the house but the walls and floors take a long time to heat from 'cold'. so if we are going away for a single night then leaving the thermostat on makes sense but if we are going away for longer then turning it off and using the app to turn the heating on in advance of us coming home to let it start warming makes sense. 

BUFF

ariarnia said:

Qyburn said:

Aside from heat pumps this myth has been around ever since people had the simplest time clock and the answer is always "no".  There is some slight confusion with commercial buildings where a higher set back temperature has to be used because otherwise the heating can't get the building up to temperature in time.  One local example where a school ran out of oil over Christmas holidays, and it took four days before they could open.

i dont think its always no. i think it depends on the house. how often someone is home. the 'comfort' temp. the efficiency of the boiler and flow temp (so how quickly it can get the house to temp). 

for us someone is almost always in the house so the the thermostat works and turning on and off to maintain the temp it wouldn't be any cheaper. and our house is old with thick walls so if we go away and leave the heating off in winter it can take a couple of days before the house feels warm again and the damp is chased out. not just the air in the house but the walls and floors take a long time to heat from 'cold'. so if we are going away for a single night then leaving the thermostat on makes sense but if we are going away for longer then turning it off and using the app to turn the heating on in advance of us coming home to let it start warming makes sense. 

This. It depends ... almost every situation is different in terms of fabric, heating system, local weather & user behaviour (many people will have limits to what they will put up with) & lifestyle . Consequently there is no 1 answer applicable  to all.

Spoonie_Turtle

We have a heat pump.  I'm probably not actually qualified to comment as I'm only just learning about it, but we will be considering turning ours off in summer because the vampire load of 1-2kWh per day for 0 output of heating is absolutely horrendous.

We've turned the hot water to only be allowed to run during a few hours in the morning.  It was set to 50℃ going down to 40℃, able to heat any time, now the temperature is the same but with a shorter window where it's allowed to heat.  October used less energy for DHW than September (made the changes halfway through September) and almost as little energy as August when we had a heatwave and were away for two weeks.

Heating, I can't be sure yet.  It kicked in halfway through September and has been on at some point every day since.  We changed the settings so it's not allowed on between 10pm and sometime early in the morning, but we don't want the house stone cold for people getting up for work, having a wash etc. so it's allowed on quite early, from something like 4.30am (I can't remember exactly).  Better than it kicking in at 3am when it's definitely not needed, which it was doing regularly before!  
Results?  It consumed marginally less in September when we had heating for two weeks than it consumed in August for 0 heat, and October consumed double than September but for more than triple heating output.  The real test will be the consumption/output values by the end of the year compared with last, but I am aware this year is even milder than last and I didn't know anything about it to keep records before recently so any difference will have to be very significant indeed to be able to attribute it to the settings change.

Edit: ours seems to be a cold house, the heating only comes on if the thermostat registers it dropping below 18℃.  Many members on the forum are finding their internal temps are still above that, but as I said, our heating kicked in halfway through September so evidently the temperature keeps going below that.