Optimising a heat pump

System

This discussion was created from comments split from: Is switching to electric heating a bad idea.

TroubledTarts

Spoonie_Turtle said:

TroubledTarts said:

Spoonie_Turtle said:

TroubledTarts said:

QrizB said:

Here are those calculations I promised.

Gas boiler.

• Ofgem national average gas consumption: 11500kWh/yr.
• Capped tariff 6.34p/kWh + 31.65p/day.
• Total annual cost (11500x0.0634 + 365x31.65) = £844.62.

Electric boiler.

• Equivalent electricity demand to match a 90% efficient gas boiler: 11500x0.9 = 10350kWh/yr.
• Capped tariff 24.86p/kWh + zero extra standing charge.
  
• Total annual cost (10350x0.2486) = £2573.01.

Heat pump.

• Equivalent electricity demand at COP of 3 to match a 90% efficient gas boiler: 11500x0.9/3 = 3450kWh/yr.
• Capped tariff 24.86p/kWh + zero extra standing charge.
  
• Total annual cost (3450x0.2486) = £857.67.

So replacing a gas boiler with an electric one, in Ofgem's average UK home, would add an extra £1728.39 a year to your energy bill. Replacing it with a heat pump would only add £13.05.

Your gas figure per kwh should have been 6.34p+10% as a boiler won't be 100% efficient I think I have read it right 

He accounted for that in the electricity calculations, using 90% efficiency to make sure the amounts of energy in kWh are equivalent.

Ah yes I see that now by why the low cop.

Why be accurate with 10% for gas but such a low cop on ASHP where even with our aging heat pump it's 3.6.

Is a cop of 3 the recognized industry mark?

I don't know but a lot of heat pumps are installed in social housing, so the residents haven't had a choice or read up on the intricacies of how to get the best out of them, and chances are the installers aren't experts either.  Our experience was they set it for continuous heat and hot water rather than efficiency, told us to touch nothing except the wall controller, and left us with zero helpful info whatsoever.  If anything goes wrong, we're to call the Housing Association, we weren't even given basic troubleshooting info.

The little I've learned to enable us to get to a COP above 3 (from 2.6) has all been online, and at the prompting of this board because I didn't even know we could change settings to make it more efficient.  And I cannot imagine that our situation is/was in any way unique, if the thousands of social housing heat pump installations tend to be left set for 24/7 heat and hot water rather than any real efficiency considerations and given a similar amount of information, i.e. none useful.

Yeah I have been trying to find some figures that suggest 3 is the.... mm whatever expected figure when calculating electricity v gas or is it just a number we have all become used to when comparing gas and electricity prices and in particular heat pumps.

Then we have the curve ball that there are no gas boiler specific tariffs but there are heat pump ones which come in cheaper than the price cap rates. I do wonder how many people run their heat pumps on the SVT and now you have me thinking what's the percentage of housing association v private installs and does that sway the COP.

And apologies @qrizb missed the reduction on the electricity calcs.

matelodave

Have a shufti here to get a feel of what sort of COP and SCOP people can get from their heatpumps - https://heatpumpmonitor.org/

However bear in mind that these are results from those who have put in a lot of effort into tweaking and monitoring their installations to get them optimised.

They are probably significantly better than that which actually gets achieved by the average guy who gets one installed by a housing association or tries to run it like a gas boiler or wants hot radiators and scalding hot water, rather than lukewarm.

IMO if you do your calculations on a SCOP of 3 to 3.5 then you wont wont go far wrong for most people. You have to put quite a bit of effort in to get it up to or even over four and many people cant or wont understand or bother to try and do it.

Also bear in mind that SCOP (or SPF) is not the same as COP. SCOP is the average over a long period, usually a year whereas COP is an instantaneous figure and will vary minute by minute even and will be a lot lower in the winter than it is in the summer.

TroubledTarts

matelodave said:

Have a shufti here to get a feel of what sort of COP and SCOP people can get from their heatpumps 

However bear in mind that these are results from those who have put in a lot of effort into tweaking and monitoring their installations to get them optimised.

They are probably significantly better than that which actually gets achieved by the average guy who gets one installed by a housing association or tries to run it like a gas boiler or wants hot radiators and scalding hot water, rather than lukewarm.

IMO if you do your calculations on a SCOP of 3 to 3.5 then you wont wont go far wrong for most people. You have to put quite a bit of effort in to get it up to or even over four and many people cant or wont understand or bother to try and do it.

Also bear in mind that SCOP (or SPF) is not the same as COP. SCOP is the average over a long period, usually a year whereas COP is an instantaneous figure and will vary minute by minute even and will be a lot lower in the winter than it is in the summer.

Yes I do wonder if the top of the scops on heat pumpmonitor bend the results and don't quite heat a home as many would like. I think the scops of 4 and a bit higher are achievable but when nearly getting to 5 that's just fudging and beyond most to be bothered with just to be top of the league.

I agree maybe a scop of 3-3.5 so 3.25 should be the new average we all talk about rather than 3.

With our Cosy tariff we averaged 17.1p kwh in January. That's the first full month but a good indicator for winter months as it was blimming cold.

So with gas running at 7p with 10% inefficiency built into that price a heat pump specific tariffs may mean at a scop of 2.44 the heat pump beats gas (that's without the £110 saving on having no gas SC)

QrizB

TroubledTarts said:

Ah yes I see that now by why the low cop.
Why be accurate with 10% for gas but such a low cop on ASHP where even with our aging heat pump it's 3.6.
Is a cop of 3 the recognized industry mark?

COPs are an eternal source of debate, but usually on the "heat pumps" subforum or the "green & ethical" board rather than over here! Usually, it's well-intentioned and well-informed prople arguing that a COP of 3 is optimistic and we should use a lower number in these comparisons. It mkes a change to have someone arguing that the illustrative COP should be higher than 3, not lower.

There have been various real-world trials and studies, involving ordinary people rather than heat pump enthusiasts. The three that usually get mentioned are:

• The Energy Saving Trust trials from 2008-2013. The median COP for ASHPs was 2.45.
• The RHPP trial from 2017. Performance had improved slightly, with a median COP for ASHPs of 2.65.
• The Electrification of Heat trial from 2021-23. Another slight improvement, with a median COP of 2.80.

You might argue that technology has mocved on from the 2000s and 2010s, but the last of those trials used equipment and installation standards that remain applicable today. As a result, I'm very reluctant to use a COP that's better than 3 when illustrating costs for heat pumps.

It's also apparent from the number of people we get posting on the forums here saying "my brand-new heat pump's expensive to run and I'm still cold" that you're not guaranteed to get decent performance without careful tweaking, even when installed today.

See also this thread where we've been discussing the diminishing returns seen from COP improvements, and what it's worth spending to improve that number.

TroubledTarts

matt_drummer said:

TroubledTarts said:

Yes I do wonder if the top of the scops on heat pumpmonitor bend the results and don't quite heat a home as many would like. I think the scops of 4 and a bit higher are achievable but when nearly getting to 5 that's just fudging and beyond most to be bothered with just to be top of the league.

I am fourth on the list. The first one is a GSHP and the second doesn't heat DHW with their heat pump. The third one is a nice Viessman heat pump. Mine is a Daikin installed by Octopus.

My house is heated to between 22c and 23c downstairs and 19c to 21c upstairs.

The ones I have looked into in the summer appeared to be running heating even then to boost their scop where they could get a cop of 5+ as it was so warm outside on many days when most people wouldn't run their heat pumps at all they would infact have them off for heating until winter hit again. (So less real life scenario more a climb to the top of the scops)

TroubledTarts

TroubledTarts said:

QrizB said:

TroubledTarts said:

Ah yes I see that now by why the low cop.
Why be accurate with 10% for gas but such a low cop on ASHP where even with our aging heat pump it's 3.6.
Is a cop of 3 the recognized industry mark?

COPs are an eternal source of debate, but usually on the "heat pumps" subforum or the "green & ethical" board rather than over here! Usually, it's well-intentioned and well-informed prople arguing that a COP of 3 is optimistic and we should use a lower number in these comparisons. It mkes a change to have someone arguing that the illustrative COP should be higher than 3, not lower.

There have been various real-world trials and studies, involving ordinary people rather than heat pump enthusiasts. The three that usually get mentioned are:

• The from 2008-2013. The median COP for ASHPs was 2.45.
• Therom 2017. Performance had improved slightly, with a median COP for ASHPs of 2.65.
• The  from 2021-23. Another slight improvement, with a median COP of 2.80.

You might argue that technology has mocved on from the 2000s and 2010s, but the last of those trials used equipment and installation standards that remain applicable today. As a result, I'm very reluctant to use a COP that's better than 3 when illustrating costs for heat pumps.

It's also apparent from the number of people we get posting on the forums here saying "my brand-new heat pump's expensive to run and I'm still cold" that you're not guaranteed to get decent performance without careful tweaking, even when installed today.

See alsowhere we've been discussing the diminishing returns seen from COP improvements, and what it's worth spending to improve that number.

Of course we generally on heat of problems not the successes that's the nature of forums. Otherwise we would brand everything produced as not up to spec and crap.

Thanks for the links btw but yes we'll out of date and it would be nice for us all to get some up to date figures.

Apologies I cannot edit posts for some reason and that may have made little sense.

I was alluding to the fact we will predominantly hear about issues on forums not successes so it's not a surprise we only hear about poor installs and poor running costs.

TroubledTarts

matt_drummer said:

TroubledTarts said:

Yes I do wonder if the top of the scops on heat pumpmonitor bend the results and don't quite heat a home as many would like. I think the scops of 4 and a bit higher are achievable but when nearly getting to 5 that's just fudging and beyond most to be bothered with just to be top of the league.

I am fourth on the list. The first one is a GSHP and the second doesn't heat DHW with their heat pump. The third one is a nice Viessman heat pump. Mine is a Daikin installed by Octopus.

My house is heated to between 22c and 23c downstairs and 19c to 21c upstairs.

To be clear this was not personally aimed at you and by way of example our heat pump last year was turned off mid April to well passed mid October (6 months not hearing the house) just hot water which as most know is a lower cop.

What I have seen on some of the top of the scops is them being run when, in my opinion, most would have them off during the warmer months and this is where they could achieve the cop of 6-7 that then bump up the scop stats for the year.

Spoonie_Turtle

TroubledTarts said:

matt_drummer said:

TroubledTarts said:

Yes I do wonder if the top of the scops on heat pumpmonitor bend the results and don't quite heat a home as many would like. I think the scops of 4 and a bit higher are achievable but when nearly getting to 5 that's just fudging and beyond most to be bothered with just to be top of the league.

I am fourth on the list. The first one is a GSHP and the second doesn't heat DHW with their heat pump. The third one is a nice Viessman heat pump. Mine is a Daikin installed by Octopus.

My house is heated to between 22c and 23c downstairs and 19c to 21c upstairs.

What do you think I am fudging?

All I do is heat my house with a heat pump and I have installed monitoring. I just worked out how to run it efficiently.

It runs continuously and used 16.6 kWh yesterday to heat the house and a tank of water at a cost of £1.20


So, @TroubledTarts, I can't wait to hear what it is that you think I have bent and fudged?

What I have seen on some of the top of the scops is them being run when, in my opinion, most would have them off during the warmer months and this is where they could achieve the cop of 6-7 that then bump up the scop stats for the year.

Does that actually happen? 

I know ours isn't a great example (and has a vampire load, to be fair) but as the weather warms up the COP absolutely plummets - I'm talking, from 3.9 in November to 1.4 in September.
(This is excluding the vampiric summer months when it can be 0.7, 0.2, 0.1, for some heat on a few chilly mornings, to literally 0 when it puts out no heat but guzzles up to 70kWh for 'heating'.)

Spoonie_Turtle

matt_drummer said:

Spoonie_Turtle said:

TroubledTarts said:

matt_drummer said:

TroubledTarts said:

Yes I do wonder if the top of the scops on heat pumpmonitor bend the results and don't quite heat a home as many would like. I think the scops of 4 and a bit higher are achievable but when nearly getting to 5 that's just fudging and beyond most to be bothered with just to be top of the league.

I am fourth on the list. The first one is a GSHP and the second doesn't heat DHW with their heat pump. The third one is a nice Viessman heat pump. Mine is a Daikin installed by Octopus.

My house is heated to between 22c and 23c downstairs and 19c to 21c upstairs.

What do you think I am fudging?

All I do is heat my house with a heat pump and I have installed monitoring. I just worked out how to run it efficiently.

It runs continuously and used 16.6 kWh yesterday to heat the house and a tank of water at a cost of £1.20


So, @TroubledTarts, I can't wait to hear what it is that you think I have bent and fudged?

What I have seen on some of the top of the scops is them being run when, in my opinion, most would have them off during the warmer months and this is where they could achieve the cop of 6-7 that then bump up the scop stats for the year.

Does that actually happen? 

I know ours isn't a great example (and has a vampire load, to be fair) but as the weather warms up the COP absolutely plummets - I'm talking, from 3.9 in November to 1.4 in September.
(This is excluding the vampiric summer months when it can be 0.7, 0.2, 0.1, for some heat on a few chilly mornings, to literally 0 when it puts out no heat but guzzles up to 70kWh for 'heating'.)

I don't think you have a vampire load, you have a circulation pump running continuously would be my guess, drawing 50W to 70w continuously.

Check your settings.

If you don't need heating just turn it off at the isolation switch if you can't work out what is wrong with the settings, then it will use nothing.

Turning heat pumps on for quick `blasts' of heat on a few chilly mornings is likely to be inefficient, a lot heat pumps are not great at the beginning of a heating cycle.

We hear the circulation pump at night when it's cold, which as far as I can gather is the … frost stat? Something to do with not freezing anyway - but not at other times.

What settings should I check?

If it were my house and my responsibility I would turn it off at the isolation switch, but it's not and my parents aren't willing to risk it.  A few times the system has disconnected itself, or not reconnected after a power cut, and they don't want to run the risk of making it happen yet more often as every time it does we have to wait for someone to come out to fix it.  (Plus we do still use hot water in the summer months, and again if it were just me I would be willing to try and put up with the inconvenience of having to boil a kettle, but my parents have had enough decades of being cold and everything always being awkward and inconvenient so I'm not going to ask them to do that when they don't have to.)

The best I can try this year is prohibiting heating and hot water while we go away.  We prohibited heating last year in the summer and it still guzzled the same amounts of energy, so we ended up being cold in September for nothing!

[The bits of heating on chilly spring/summer mornings were the heating automatically kicking in as the room remp dropped below the thermostat setting, not us choosing to turn it on, just in case that wasn't clear.]

TroubledTarts

Spoonie_Turtle said:

TroubledTarts said:

matt_drummer said:

TroubledTarts said:

Yes I do wonder if the top of the scops on heat pumpmonitor bend the results and don't quite heat a home as many would like. I think the scops of 4 and a bit higher are achievable but when nearly getting to 5 that's just fudging and beyond most to be bothered with just to be top of the league.

I am fourth on the list. The first one is a GSHP and the second doesn't heat DHW with their heat pump. The third one is a nice Viessman heat pump. Mine is a Daikin installed by Octopus.

My house is heated to between 22c and 23c downstairs and 19c to 21c upstairs.

What do you think I am fudging?

All I do is heat my house with a heat pump and I have installed monitoring. I just worked out how to run it efficiently.

It runs continuously and used 16.6 kWh yesterday to heat the house and a tank of water at a cost of £1.20


So, @TroubledTarts, I can't wait to hear what it is that you think I have bent and fudged?

What I have seen on some of the top of the scops is them being run when, in my opinion, most would have them off during the warmer months and this is where they could achieve the cop of 6-7 that then bump up the scop stats for the year.

Does that actually happen? 

I know ours isn't a great example (and has a vampire load, to be fair) but as the weather warms up the COP absolutely plummets - I'm talking, from 3.9 in November to 1.4 in September.
(This is excluding the vampiric summer months when it can be 0.7, 0.2, 0.1, for some heat on a few chilly mornings, to literally 0 when it puts out no heat but guzzles up to 70kWh for 'heating'.)

It really does happen with some. For some SCOP is the be all and end all of life hence that heat monitor leader board

The rest of us do the sensible thing and turn the heating off 6 months of the year and instead of upping our scop with heating when it's not required we just put up with the winter time only scop.(Note this might have been passed down in generations of turning the heating off in April and not back on til October/November 🤣)

Turning the heating off for those 6 months will mean less kwh used but lower scop overall (of course those with solar and battery they can up their scop all summer if they like to be top of the scops as it will be free energy) albeit they can't export that used energy for profit if they use it on unnecessary heating and scop boosting.

In the summer if it's 10-20oC outside definitely 5-7+ cop is achievable.

On to your vampire load what make and model is your heat pump as I have read that some have been reported to have this issue in the region of 2.4kwh for the day.