People Saying Heat Pumps are Rubbish - Are They?

michaels

MeteredOut said:

FreeBear said:

MeteredOut said:

FreeBear said:

MeteredOut said:

Nick_Dr1 said:

MeteredOut said:

In the case of Heat Pumps, the starting position I hear is that any house can be converted to work with a heat pump with running costs lower than or equivalent to a gas boiler and that any negative reports we see are due to badly spec'd/installed/configured systems.

I'm not convinced it is a simple as that.

What can never be defined without more detailed investigation is what work is needed to get any individual house "heat pump ready" so that running costs are lower or equivalent to a gas boiler.

eg, I have a house with a large floor space with water underfloor heating throughout downstairs and traditional radiators upstairs, but fairly poorly insulated, all powered from a 40kW gas boiler. I know it should be possible to get a Heat Pump working, but there's a lot of work to do to get it there - my (admittedly fairly rudimentary to date) look into this makes me believe simply swapping out the gas boiler for a heat pump would never suffice.

It is as simple as that. The system just needs to be designed such that heat in > heat out. This works for any heat source. Its just more nuanced for heatpumps as they don't crank out large amounts of heat in a short period like an oversized gas boiler.
A heatpump system needs to be designed, by someone who understands what they are doing. This includes understanding heat loss, heat transfer of radiators and heat flow rate though pipes. And that's it.
Get it wrong though and there's nowhere to go. With a gas boiler you normally have excess heat capability to allow for incompetent heat flow design.
What this means is that "standard" houses can have a "standard" design. Unusual houses need bespoke design by someone who knows what they are doing. So it is all about the spec.

What about a hot water tank? The only place one could go in my property is a loft space (low height as we have a high ceilings) and that would either require major work to run new pipes, or lengthy runs if existing pipes were to be used (ie, the run from where the boiler is and a heat pump would go to the loft space and back would be quite legthy).

Though maybe I will get someone out to see what they suggest might be possible. The boiler is 15+ years old now and had its first leak this year (simple parts replacement) so its probably best I plan ahead.

A few solutions spring to mind.

A horizontally mounted tank up in the loft. Downside is getting a tank up there, and ensuring there is sufficient structural support (but that would apply to a vertical tank also).

Construct a well insulated shed just outside the house to house the DHW tank plus ancillaries - Extra expense, and may not be practical. But I do know of at least one installation that went that route.

A Heat Geek mini store - Small enough to fit inside a kitchen cupboard, although total DHW supply from one charge may not be sufficient for your needs if you go for a smaller unit.

Finally, if you don't need copious quantities of hot water and just have a shower, instant water heaters at the point of use could be used.

We have 4 bathrooms and although its unusual for more than 2 showers to be running at one time, it can happen when we have visitors. The existing 40kW boiler just about copes, but I have to pre-emptively increase the HW temperature from the low setting I usually have it at.

With four bathrooms, do you not have a DHW tank already ?

No, so it might struggle with simultaneous 4 showers today, but its not caused us a problem. We rarely have more than 2 showers at any one time., but if needed, ramping up the HW temperature at the boiler and lowering the shower thermostats so the mix is less HW and more CW just about makes it viable. 

You are lucky to have enough water pressure - apparently the minimum standard is 1bar which is all we get in the mornings

grumpypensioner

grumpypensioner said:

QrizB said:

benson1980 said:

grumpypensioner said:

I found a bit of a solution, I purchase a standalone air conditioner unit to supplement my old Baxi gas boiler, with a new Wessex 1.47kw 12000 BTU unit from ToolStation (over 200% efficiency) which cost me under £400 installed (needs a standard 10cm wall air duct and drain pipes and just plugs into a 13 amp socket)

That setup certainly does sound like a compromise. Why does your boiler not meet your heating requirements and how can it be more cost effective to run an electric heat source at 200% efficiency? The only way it could be is if you are using it to heat one room, shutting doors of rooms you aren’t using much, and switching off your central heating completely I’m guessing? 

There's a place for those one-hose portable heat pumps (I've got one myself that only cools) but they all have the same limitation, namely that the (cold/hot) air that they vent when (heating/cooling) comes from inside the house and is air that you've previously (heated/cooled). And it's replaced by (cold/hot) air from outside.

This limits their COP considerably, compared to a two hose, ducted or split system where the inside air stays inside and the outside air, outside.

QrizB said:

benson1980 said:

grumpypensioner said:

I found a bit of a solution, I purchase a standalone air conditioner unit to supplement my old Baxi gas boiler, with a new Wessex 1.47kw 12000 BTU unit from ToolStation (over 200% efficiency) which cost me under £400 installed (needs a standard 10cm wall air duct and drain pipes and just plugs into a 13 amp socket)

That setup certainly does sound like a compromise. Why does your boiler not meet your heating requirements and how can it be more cost effective to run an electric heat source at 200% efficiency? The only way it could be is if you are using it to heat one room, shutting doors of rooms you aren’t using much, and switching off your central heating completely I’m guessing? 

There's a place for those one-hose portable heat pumps (I've got one myself that only cools) but they all have the same limitation, namely that the (cold/hot) air that they vent when (heating/cooling) comes from inside the house and is air that you've previously (heated/cooled). And it's replaced by (cold/hot) air from outside.

This limits their COP considerably, compared to a two hose, ducted or split system where the inside air stays inside and the outside air, outside.

Yup I expect your are all right, but it don't half work well! My old gas back boiler (with a front fire) is over 40 years old, is self maintained because it is so simple and hasn't cost me any maintenance (I just give it a blast with compressed air and a vacuum). It runs two downstairs radiators and provides excellent hot water at 55ºC and a warm drying cupboard. It is switched off from 6.30 pm to 6.30am (we retire early and don't have to get up early for work!). We have a 35 year old Daikin external heat pump (also zero maintenance) which keeps the upstairs warm - and cool when needed. I purchase the additional Wessex unit for the front room primarily for cooling because my wife suffers the heat (and cold fluctuations) but I found it to be perfect for boosting the temperature during cold periods first thing in the morning before the radiators had time to work, it only takes an hour or two while we get up. Then thanks to my smart energy meter and courtesy of BG I was able to track and compare usage over the past years which showed a significant drop annually but it could be just the weather! Because it allowed me to reduce the temperature and thus load on my main boiler. The point being is that I have had minimal capital outlay for an improvement, and we are very comfortable so it is a good compromise. Instead of spending £10,000 (?) on a complete new system so my ISA's interest pays for any inefficiencies and I don't have any maintenance costs.....
I think key factors may be the speed of response, it is powerful and circulates air around the house, and to quote an old tv clip is very on and offable!

"And it's replaced by (cold/hot) air from outside."
Think it is called ventilation.

silverwhistle

FreeBear said:

A very rough rule of thumb to determine the size of a heat pump needed is to take your annual gas consumption (in kWh) and divide it by 2900. But if you are like me and supplement heating with a wood stove, it is going to throw the calculation out. In which case, Heat Geek has a handy rough estimation table -> https://www.heatgeek.com/how-to-size-my-heat-pump-or-boiler-heat-loss-cheat-sheet/ 

Hmm, my usage last year was 2800 and something, I also use a woodburner, rarely have the GCH on and not bothered about heating upstairs unless in very cold weather: up to bed and under the covers and getting up and moving in the morning.. Electric shower and towel rail which I sometimes heat at cheap overnight rate or surplus solar which also goes into the immersion. In a cavity wall insulated older 3 bed terrace losses aren't great.

Which rate did you use in your calculations? Seems to me an A2A heat pump for downstairs (lounge and diner) would have to be one of the lowest powered available?

Spies

grumpypensioner said:

grumpypensioner said:

QrizB said:

benson1980 said:

grumpypensioner said:

I found a bit of a solution, I purchase a standalone air conditioner unit to supplement my old Baxi gas boiler, with a new Wessex 1.47kw 12000 BTU unit from ToolStation (over 200% efficiency) which cost me under £400 installed (needs a standard 10cm wall air duct and drain pipes and just plugs into a 13 amp socket)

That setup certainly does sound like a compromise. Why does your boiler not meet your heating requirements and how can it be more cost effective to run an electric heat source at 200% efficiency? The only way it could be is if you are using it to heat one room, shutting doors of rooms you aren’t using much, and switching off your central heating completely I’m guessing? 

There's a place for those one-hose portable heat pumps (I've got one myself that only cools) but they all have the same limitation, namely that the (cold/hot) air that they vent when (heating/cooling) comes from inside the house and is air that you've previously (heated/cooled). And it's replaced by (cold/hot) air from outside.

This limits their COP considerably, compared to a two hose, ducted or split system where the inside air stays inside and the outside air, outside.

QrizB said:

benson1980 said:

grumpypensioner said:

I found a bit of a solution, I purchase a standalone air conditioner unit to supplement my old Baxi gas boiler, with a new Wessex 1.47kw 12000 BTU unit from ToolStation (over 200% efficiency) which cost me under £400 installed (needs a standard 10cm wall air duct and drain pipes and just plugs into a 13 amp socket)

That setup certainly does sound like a compromise. Why does your boiler not meet your heating requirements and how can it be more cost effective to run an electric heat source at 200% efficiency? The only way it could be is if you are using it to heat one room, shutting doors of rooms you aren’t using much, and switching off your central heating completely I’m guessing? 

There's a place for those one-hose portable heat pumps (I've got one myself that only cools) but they all have the same limitation, namely that the (cold/hot) air that they vent when (heating/cooling) comes from inside the house and is air that you've previously (heated/cooled). And it's replaced by (cold/hot) air from outside.

This limits their COP considerably, compared to a two hose, ducted or split system where the inside air stays inside and the outside air, outside.

Yup I expect your are all right, but it don't half work well! My old gas back boiler (with a front fire) is over 40 years old, is self maintained because it is so simple and hasn't cost me any maintenance (I just give it a blast with compressed air and a vacuum). It runs two downstairs radiators and provides excellent hot water at 55ºC and a warm drying cupboard. It is switched off from 6.30 pm to 6.30am (we retire early and don't have to get up early for work!). We have a 35 year old Daikin external heat pump (also zero maintenance) which keeps the upstairs warm - and cool when needed. I purchase the additional Wessex unit for the front room primarily for cooling because my wife suffers the heat (and cold fluctuations) but I found it to be perfect for boosting the temperature during cold periods first thing in the morning before the radiators had time to work, it only takes an hour or two while we get up. Then thanks to my smart energy meter and courtesy of BG I was able to track and compare usage over the past years which showed a significant drop annually but it could be just the weather! Because it allowed me to reduce the temperature and thus load on my main boiler. The point being is that I have had minimal capital outlay for an improvement, and we are very comfortable so it is a good compromise. Instead of spending £10,000 (?) on a complete new system so my ISA's interest pays for any inefficiencies and I don't have any maintenance costs.....
I think key factors may be the speed of response, it is powerful and circulates air around the house, and to quote an old tv clip is very on and offable!

"And it's replaced by (cold/hot) air from outside."
Think it is called ventilation.

No, it's called negative pressure, ventilation is completely different.

You can control ventilation, with your single hose AC the external air is always fighting against you, if it's cold and you're trying to warm the interior, it's pulling more cold air through every crack and crevice as the unit is pumping interior air, outside, and vise versa when it's hot outside and you're trying to cool

FreeBear

silverwhistle said:

FreeBear said:

A very rough rule of thumb to determine the size of a heat pump needed is to take your annual gas consumption (in kWh) and divide it by 2900. But if you are like me and supplement heating with a wood stove, it is going to throw the calculation out. In which case, Heat Geek has a handy rough estimation table -> https://www.heatgeek.com/how-to-size-my-heat-pump-or-boiler-heat-loss-cheat-sheet/ 

Hmm, my usage last year was 2800 and something, I also use a woodburner, rarely have the GCH on and not bothered about heating upstairs unless in very cold weather: up to bed and under the covers and getting up and moving in the morning.. Electric shower and towel rail which I sometimes heat at cheap overnight rate or surplus solar which also goes into the immersion. In a cavity wall insulated older 3 bed terrace losses aren't great.

Which rate did you use in your calculations? Seems to me an A2A heat pump for downstairs (lounge and diner) would have to be one of the lowest powered available?

When I refitted my heating system in '23, I used the Stelrad calculator to determine the radiator sizing, and then added a bit on top. Once the gas boiler was installed, I fitted a heat meter to measure just how much energy was being put in to the radiators. In my mind, a much more accurate method of determining heat demand than feeding numbers in to a spreadsheet or MCS calculator. The graphs are telling me that I only need mean of 3kW to maintain a steady 18-19°C temperature when it is around freezing point outside. Peak demand is between 7kW and 12kW depending on how fast I want the place to heat up and the maximum flow temperature.

Based on that data, I reckon an ASHP of around 7kW would be sufficient. Could perhaps get away with a 6kW unit, but certainly don't need any more than 8kW. Although to be sure, really need a sustained period of subzero temperatures in order to collect more data.

michaels

FreeBear said:

silverwhistle said:

FreeBear said:

A very rough rule of thumb to determine the size of a heat pump needed is to take your annual gas consumption (in kWh) and divide it by 2900. But if you are like me and supplement heating with a wood stove, it is going to throw the calculation out. In which case, Heat Geek has a handy rough estimation table -> https://www.heatgeek.com/how-to-size-my-heat-pump-or-boiler-heat-loss-cheat-sheet/ 

Hmm, my usage last year was 2800 and something, I also use a woodburner, rarely have the GCH on and not bothered about heating upstairs unless in very cold weather: up to bed and under the covers and getting up and moving in the morning.. Electric shower and towel rail which I sometimes heat at cheap overnight rate or surplus solar which also goes into the immersion. In a cavity wall insulated older 3 bed terrace losses aren't great.

Which rate did you use in your calculations? Seems to me an A2A heat pump for downstairs (lounge and diner) would have to be one of the lowest powered available?

When I refitted my heating system in '23, I used the Stelrad calculator to determine the radiator sizing, and then added a bit on top. Once the gas boiler was installed, I fitted a heat meter to measure just how much energy was being put in to the radiators. In my mind, a much more accurate method of determining heat demand than feeding numbers in to a spreadsheet or MCS calculator. The graphs are telling me that I only need mean of 3kW to maintain a steady 18-19°C temperature when it is around freezing point outside. Peak demand is between 7kW and 12kW depending on how fast I want the place to heat up and the maximum flow temperature.

Based on that data, I reckon an ASHP of around 7kW would be sufficient. Could perhaps get away with a 6kW unit, but certainly don't need any more than 8kW. Although to be sure, really need a sustained period of subzero temperatures in order to collect more data.

I can also see my half hourly gas input which with a modulating gas boiler is pretty constant.  However I think to get the grant you need enough heat to meet the MCS calculation standard (including about 22C in main rooms and 18C in bedrooms), regardless of what you actually know you need! 

Reed_Richards

michaels said:

FreeBear said:

silverwhistle said:

FreeBear said:

A very rough rule of thumb to determine the size of a heat pump needed is to take your annual gas consumption (in kWh) and divide it by 2900. But if you are like me and supplement heating with a wood stove, it is going to throw the calculation out. In which case, Heat Geek has a handy rough estimation table -> https://www.heatgeek.com/how-to-size-my-heat-pump-or-boiler-heat-loss-cheat-sheet/ 

Hmm, my usage last year was 2800 and something, I also use a woodburner, rarely have the GCH on and not bothered about heating upstairs unless in very cold weather: up to bed and under the covers and getting up and moving in the morning.. Electric shower and towel rail which I sometimes heat at cheap overnight rate or surplus solar which also goes into the immersion. In a cavity wall insulated older 3 bed terrace losses aren't great.

Which rate did you use in your calculations? Seems to me an A2A heat pump for downstairs (lounge and diner) would have to be one of the lowest powered available?

When I refitted my heating system in '23, I used the Stelrad calculator to determine the radiator sizing, and then added a bit on top. Once the gas boiler was installed, I fitted a heat meter to measure just how much energy was being put in to the radiators. In my mind, a much more accurate method of determining heat demand than feeding numbers in to a spreadsheet or MCS calculator. The graphs are telling me that I only need mean of 3kW to maintain a steady 18-19°C temperature when it is around freezing point outside. Peak demand is between 7kW and 12kW depending on how fast I want the place to heat up and the maximum flow temperature.

Based on that data, I reckon an ASHP of around 7kW would be sufficient. Could perhaps get away with a 6kW unit, but certainly don't need any more than 8kW. Although to be sure, really need a sustained period of subzero temperatures in order to collect more data.

I can also see my half hourly gas input which with a modulating gas boiler is pretty constant.  However I think to get the grant you need enough heat to meet the MCS calculation standard (including about 22C in main rooms and 18C in bedrooms), regardless of what you actually know you need! 

Which is as it should be, because the grant is essentially for the house and so should meet the needs of subsequent occupants after the current owner has moved on.

MarzipanCrumble

michaels said:

FreeBear said:

silverwhistle said:

FreeBear said:

A very rough rule of thumb to determine the size of a heat pump needed is to take your annual gas consumption (in kWh) and divide it by 2900. But if you are like me and supplement heating with a wood stove, it is going to throw the calculation out. In which case, Heat Geek has a handy rough estimation table -> https://www.heatgeek.com/how-to-size-my-heat-pump-or-boiler-heat-loss-cheat-sheet/ 

Hmm, my usage last year was 2800 and something, I also use a woodburner, rarely have the GCH on and not bothered about heating upstairs unless in very cold weather: up to bed and under the covers and getting up and moving in the morning.. Electric shower and towel rail which I sometimes heat at cheap overnight rate or surplus solar which also goes into the immersion. In a cavity wall insulated older 3 bed terrace losses aren't great.

Which rate did you use in your calculations? Seems to me an A2A heat pump for downstairs (lounge and diner) would have to be one of the lowest powered available?

When I refitted my heating system in '23, I used the Stelrad calculator to determine the radiator sizing, and then added a bit on top. Once the gas boiler was installed, I fitted a heat meter to measure just how much energy was being put in to the radiators. In my mind, a much more accurate method of determining heat demand than feeding numbers in to a spreadsheet or MCS calculator. The graphs are telling me that I only need mean of 3kW to maintain a steady 18-19°C temperature when it is around freezing point outside. Peak demand is between 7kW and 12kW depending on how fast I want the place to heat up and the maximum flow temperature.

Based on that data, I reckon an ASHP of around 7kW would be sufficient. Could perhaps get away with a 6kW unit, but certainly don't need any more than 8kW. Although to be sure, really need a sustained period of subzero temperatures in order to collect more data.

I can also see my half hourly gas input which with a modulating gas boiler is pretty constant.  However I think to get the grant you need enough heat to meet the MCS calculation standard (including about 22C in main rooms and 18C in bedrooms), regardless of what you actually know you need! 

And for a HP I won't want that - I want cooler bedroom (I like duvets and weight) but a constant 20 ish downstairs if I could.  Preently GCH but thinking about HP

matelodave

MarzipanCrumble said:

michaels said:

FreeBear said:

silverwhistle said:

FreeBear said:

A very rough rule of thumb to determine the size of a heat pump needed is to take your annual gas consumption (in kWh) and divide it by 2900. But if you are like me and supplement heating with a wood stove, it is going to throw the calculation out. In which case, Heat Geek has a handy rough estimation table -> https://www.heatgeek.com/how-to-size-my-heat-pump-or-boiler-heat-loss-cheat-sheet/ 

Hmm, my usage last year was 2800 and something, I also use a woodburner, rarely have the GCH on and not bothered about heating upstairs unless in very cold weather: up to bed and under the covers and getting up and moving in the morning.. Electric shower and towel rail which I sometimes heat at cheap overnight rate or surplus solar which also goes into the immersion. In a cavity wall insulated older 3 bed terrace losses aren't great.

Which rate did you use in your calculations? Seems to me an A2A heat pump for downstairs (lounge and diner) would have to be one of the lowest powered available?

When I refitted my heating system in '23, I used the Stelrad calculator to determine the radiator sizing, and then added a bit on top. Once the gas boiler was installed, I fitted a heat meter to measure just how much energy was being put in to the radiators. In my mind, a much more accurate method of determining heat demand than feeding numbers in to a spreadsheet or MCS calculator. The graphs are telling me that I only need mean of 3kW to maintain a steady 18-19°C temperature when it is around freezing point outside. Peak demand is between 7kW and 12kW depending on how fast I want the place to heat up and the maximum flow temperature.

Based on that data, I reckon an ASHP of around 7kW would be sufficient. Could perhaps get away with a 6kW unit, but certainly don't need any more than 8kW. Although to be sure, really need a sustained period of subzero temperatures in order to collect more data.

I can also see my half hourly gas input which with a modulating gas boiler is pretty constant.  However I think to get the grant you need enough heat to meet the MCS calculation standard (including about 22C in main rooms and 18C in bedrooms), regardless of what you actually know you need! 

And for a HP I won't want that - I want cooler bedroom (I like duvets and weight) but a constant 20 ish downstairs if I could.  Preently GCH but thinking about HP

You do realise that you can turn them down but its a lot more difficult get get more heat out if they are undersized. Likewise they also cost more to run if you have to crank up the temperature to try and compensate for an undersized unit.

If you presently have GCH, why are you considering getting a heatpump. Its unlikely to save you much if any money unless you can get it properly optimised and run it properly and even then you need to get an SCOP of better than four and maybe fiddle around with TOU electricity tariffs.

I've got a heatpump, had it for 15 years and I'm more than happy with it but I wouldn't swap out a functioning gas boiler for one and, TBH, I'd still replace a gas boiler like for like at the moment until HP's get cheaper to install and the price of leccy gets a lot closer to the price of gas.

grumpypensioner

Hope all you pundits watched the channel 5 programme called "Heat Pumps: Are They Really Worth It?" on 21 May 2025 19.00. Mind and cash boggling. Definitely convinces me that one large all encompassing system is not the way to go.