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

Cardew

wooried said:

This thread seems to ignore heat pump based systems. They have very different characteristics to conventional ones - specially when combined with underfloor pipes rather than radiators. Our hot water is also produced by the  ASHP and has a timed boost facility so that water can be cooler outside showing time. We recently discovered the best time for a boost is late afternoon when the air outside is warmest. This cut the time the pump runs to heat water by a third. 

Not sure of the relevance of the point you are making to this thread.

Running your ASHP to heat the hot water when the COP(gain) is optimum is obviously sensible. In the same way if you have an Economy 7 tariff you would use the cheap rate where possible.

The central issue is that it is not cheaper to run heating constantly; albeit it is usually necessary to run a heat pump for much longer periods than conventional CH. However this isn't for reasons of economy, but because a heat pump usually runs at a lower water temperature and takes longer to bring a room back up to temperature.

coffeehound

Cardew said:

The central issue is that it is not cheaper to run heating constantly; albeit it is usually necessary to run a heat pump for much longer periods than conventional CH. However this isn't for reasons of economy, but because a heat pump usually runs at a lower water temperature and takes longer to bring a room back up to temperature.

I suppose the equivalent question relating to heat pumps would be:  is it cheaper to run the HP for shorter periods at higher flow temperature, or to run it 24/7 at lower temperature.  Again, as with condensing boilers, it's not so straightforward to bat away since the HP will be more efficient at lower flow temperature.

Reed_Richards

Cardew said:

... a heat pump usually runs at a lower water temperature and takes longer to bring a room back up to temperature.

There's a myth for starters.  Actually its principally the heat output capacity of your radiators that determines the time it takes to bring a room back up to temperature.  The heat source feeding the radiators has little impact, nor does the temperature of the water inside the radiators provided it is the temperature they were sized to run at.    I have argued this point previously with @Cardew but they refuse to accept it.       

Bricks

Reed_Richards said:

Cardew said:

... a heat pump usually runs at a lower water temperature and takes longer to bring a room back up to temperature.

There's a myth for starters.  Actually its principally the heat output capacity of your radiators that determines the time it takes to bring a room back up to temperature.  The heat source feeding the radiators has little impact, nor does the temperature of the water inside the radiators provided it is the temperature they were sized to run at.    I have argued this point previously with @Cardew but they refuse to accept it.       

There is a similar question connected to the idea that ASHPs "don't work" in uninsulated or badly insulated homes.

My understanding is that the reason they might "not work" would be if the heat output capacity of radiators wasn't enough to keep up with the rate of heat loss through the building fabric.

I can see that this could happen if you used the same radiators as you had previously used with a conventional boiler system. Similarly, a heat pump would take longer to bring a room up to temperature than a conventional system assuming the radiators aren't changed.

What I'm not clear about, is whether in an uninsulated home, it might be quite possible in theory to heat it via heat pump, but in practice the size or number of radiators would become difficult to accommodate.

Reed_Richards

Bricks said:

There is a similar question connected to the idea that ASHPs "don't work" in uninsulated or badly insulated homes.

My understanding is that the reason they might "not work" would be if the heat output capacity of radiators wasn't enough to keep up with the rate of heat loss through the building fabric.

I can see that this could happen if you used the same radiators as you had previously used with a conventional boiler system. Similarly, a heat pump would take longer to bring a room up to temperature than a conventional system assuming the radiators aren't changed.

What I'm not clear about, is whether in an uninsulated home, it might be quite possible in theory to heat it via heat pump, but in practice the size or number of radiators would become difficult to accommodate.

More myth busting:  

If you get a heat pump you will need to change the radiators.
Okay, there may be a few exceptions but so few they are not worth dealing with.

Heat pumps work perfectly well in badly-insulated homes but:
You will need a bigger one which will be proportionately more expensive than a bigger gas or oil boiler
You might well not qualify for a government subsidy.
You will indeed need radiators with an even larger total effective surface area.
 

Cardew

Reed_Richards said:

Cardew said:

albeit it is usually necessary to run a heat pump for much longer periods than conventional CH.

... a heat pump usually runs at a lower water temperature and takes longer to bring a room back up to temperature.

There's a myth for starters.  Actually its principally the heat output capacity of your radiators that determines the time it takes to bring a room back up to temperature.  The heat source feeding the radiators has little impact, nor does the temperature of the water inside the radiators provided it is the temperature they were sized to run at.    I have argued this point previously with @Cardew but they refuse to accept it.       

Usually - Usually - Usually - Usually

This Cardew doesn't 'refuse to accept' it is the heat output capacity of radiators that determine the time it takes to get the room back up to temperature.

Please don't bother to reply, just be satisfied with yourself that you have exploded yet another myth in that heat pumps don't usually need to run longer periods than conventional CH. 

C_Mababejive

Its really simple and my best advice to everyone is that where possible, switch your heating OFF and with electricity, reduce your consumption. If you see it turned on and it isnt needed, switch it off.

The best way to save energy and money is to stop those meters turning.

Since the middle of last year i have tracked energy prices and i have seen this coming. The era of flouncing around the house scantily clad is over. If its chilly, put some clothes on . Wear thick socks, put a thermal vest on as a base layer.

Its all about acclimatization. You need to retrain your body to be comfortable with lower temperatures around the home.

If your house isnt very energy efficient then retreat to the lounge for winter. Make one room warm and surrender the rest of the house. Get an electric blanket for the bed so that you are nice and warm when you get in it.

QrizB

C_Mababejive said:

The era of flouncing around the house scantily clad is over. If its chilly, put some clothes on . Wear thick socks, put a thermal vest on as a base layer.

That's really going to put a dent in my OnlyFans eanings!

Teapot55

You probably already turn the tap off nowadays when you’re brushing your teeth but there’s moneysaving ways to save hot water as well 
   •   turn the water off while you’re rubbing shampoo into your hair
   •   same for conditioner
   •   hygienic handwashing for twenty seconds can start after you’ve rubbed the soap all over your hands  
   •   if you’re a real diehard moneysaver rub the soap all over your body with a rough flannel before you put the shower back on to rinse all the soap off & it only takes twenty seconds!

Astria

C_Mababejive said:

Its really simple and my best advice to everyone is that where possible, switch your heating OFF and with electricity, reduce your consumption. If you see it turned on and it isnt needed, switch it off.

The best way to save energy and money is to stop those meters turning.

Whilst that's true for electric, for heating it will always be "it depends".

I monitor how often and for how long my gas boiler runs for and how much gas I use, and turning it off makes next to no difference to leaving it on. It's more comfortable and convenient to leave it on so that's what I do.

What I've found is that (in my particular case) leaving the heating on causes the boiler to fire about once per hour, for about 10 minutes at a time. This seems wasteful as I'm typically out or in the office at work, but if I turn it off when I leave then it can take upto 2 hours to get the house back upto temperature, and the end result is that it's on for the same amount of time anyway.

The thermostat is set at 00:00 to 18:00 is 15c, and 18:00 - 23:59 at 18c, so still in the t-shirt and shorts range.