Heat pump v Gas boiler

[nod]

We are into December So able to make a comparison between our current and previous build 

All things considered I think the HP will be the same or slightly more to run 

We didn’t have an option on this build 

Both builds are traditional Scoring about the same B89 A if we ever got the urge to add PV Which our buyers are in the process of doing 

 

While the HP works exactly the same with UFH I wouldn’t like to have to rely on Rads with a HP They are slow to heat and don’t get very hot I wouldn’t like to have to rely on Rads to heat a poorly insulated home 

The installer came back to check and set everything up for winter 

He asked if we could leave the Rads on for a few hours 

All in all we are pleasantly surprised at how straightforward a HP is and hot water on tap 24-7 is a bonus 

 

[Nickfromwales]

Any issues with freezing / defrosting over the winter? 

[ProDave]

24 minutes ago, nod said:

All in all we are pleasantly surprised at how straightforward a HP is and hot water on tap 24-7 is a bonus 

 

Why is that a surprise?  I set mine up to operate from a standard heating programmer, because that is what people understand.  And why are you surprised to have 24/7 hot water?  did you not have that with a boiler?

[sharpener]

18 hours ago, nod said:

I wouldn’t like to have to rely on Rads with a HP They are slow to heat and don’t get very hot

 

You can't generalise, it all depends on their size and how the system is configured. The rads in our sitting room were already quite big enough and the room heats up in 30 mins using stored energy from cheap electricity. Previous UFH was extremely slow to respond and the carpet didn't help either.

 

We had 6 other rads upgraded and they are now fine too. We do not heat all the house at the same time, bc it is a big house and we move about it in a well-defined pattern so it is easy to programme the system accordingly.

 

18 hours ago, nod said:

if we ever got the urge to add PV

 

With PV as cheap as it is now I would have thought that it would be a no-brainer to cover all available roof space.

[MrPotts]

PV cheap? I have had a quote for 14 panels and a 10kWh battery for a little over £14k, that’s not cheap to me. If I can get this cheaper please point me towards the right direction. 😀

[JohnMo]

10 minutes ago, MrPotts said:

PV cheap? I have had a quote for 14 panels and a 10kWh battery for a little over £14k, that’s not cheap to me. If I can get this cheaper please point me towards the right direction. 😀

PV is cheap, batteries aren't

 

Actually PV including mounts should be around or less than £200 per kW. An inverter to support couple of hundred pounds.

[sharpener]

52 minutes ago, MrPotts said:

I have had a quote for 14 panels and a 10kWh battery for a little over £14k, that’s not cheap to me.

 

I think solar installers are pushing batteries hard bc the panels have become a commodity item and there is comparatively little profit in them. Margins on the batteries are better (for now) and you can install them in the warm and dry.

The economic case for the customer is harder to establish, though now e.g. Octopus Cosy will allow you to make three full cycles in 24 hours which is a big improvement. And if you can achieve round trip efficiency >80% you can even make a margin selling their own electricity back to them. But I can't quite.

[S2D2]

18 minutes ago, sharpener said:

 

I think solar installers are pushing batteries hard bc the panels have become a commodity item and there is comparatively little profit in them. Margins on the batteries are better (for now) and you can install them in the warm and dry.

The economic case for the customer is harder to establish, though now e.g. Octopus Cosy will allow you to make three full cycles in 24 hours which is a big improvement. And if you can achieve round trip efficiency >80% you can even make a margin selling their own electricity back to them. But I can't quite.

Cosy has rapidly accelerated the payback period on my battery, three full cycles a day so saved the purchase of two additional modules. Sure, it's harder on the batteries, but you're getting the same savings just in a condensed time period.

 

~12p/kWh into a heat pump with a SCoP of around 4, just with a cheapish 2.8kWh battery. Definitely cheaper than the gas boiler.

[nod]

3 hours ago, sharpener said:

 

You can't generalise, it all depends on their size and how the system is configured. The rads in our sitting room were already quite big enough and the room heats up in 30 mins using stored energy from cheap electricity. Previous UFH was extremely slow to respond and the carpet didn't help either.

 

We had 6 other rads upgraded and they are now fine too. We do not heat all the house at the same time, bc it is a big house and we move about it in a well-defined pattern so it is easy to programme the system accordingly.

 

 

With PV as cheap as it is now I would have thought that it would be a no-brainer to cover all available roof space.

We didn’t want to cover our beautiful slate roof with horrible solar panels 

 

As stated our buyer has decided to put these things up The salesmen has predicted around £700 per year saving 

12 k supply and fit If the saving is correct and I’ve no reason to doubt a salesman 15 years to break even is a long time and the batteries will probably need replacing by then 

Definitely not a no brainer 

[sharpener]

3 hours ago, nod said:

We didn’t want to cover our beautiful slate roof with horrible solar panels 

 

Fair enough. My first ones have silver frames but the later ones are all black, not too bad on dark grey slates. And I realised this week that a house near us has black panels on black slates, so inconspicuous I had no idea they had been fitted.

 

3 hours ago, nod said:

15 years to break even is a long time and the batteries will probably need replacing by then

Yes its the batteries that tilt the economics a good deal, the PV on its own would have a lot quicker payback.

[ReedRichards]

On 10/12/2024 at 19:28, nod said:

I wouldn’t like to have to rely on Rads with a HP They are slow to heat and don’t get very hot I wouldn’t like to have to rely on Rads to heat a poorly insulated home 

 

This is entirely dependent on the size (I.e. surface area) of the radiators.  Make that surface area big enough and they will be fast to heat a room, even though they don't get very hot.  Make that surface area big enough and they will heat a poorly insulated house perfectly well.  Or if you haven't got room for a radiator with a suitably large surface area, get one that is fan-assisted.  

[nod]

34 minutes ago, ReedRichards said:

 

This is entirely dependent on the size (I.e. surface area) of the radiators.  Make that surface area big enough and they will be fast to heat a room, even though they don't get very hot.  Make that surface area big enough and they will heat a poorly insulated house perfectly well.  Or if you haven't got room for a radiator with a suitably large surface area, get one that is fan-assisted.  

I was referring to the temperature of the Rads Warm more than hot 

 

[ReedRichards]

1 hour ago, nod said:

I was referring to the temperature of the Rads Warm more than hot 

 

A fact which I acknowledged in my reply.  I've had a heat pump for 4 years now and warm radiators can provide all the heat you need.

Edited December 12 by ReedRichards

[marshian]

On 10/12/2024 at 20:28, nod said:

We are into December So able to make a comparison between our current and previous build 

All things considered I think the HP will be the same or slightly more to run 

We didn’t have an option on this build 

Both builds are traditional Scoring about the same B89 A if we ever got the urge to add PV Which our buyers are in the process of doing 

 

While the HP works exactly the same with UFH I wouldn’t like to have to rely on Rads with a HP They are slow to heat and don’t get very hot I wouldn’t like to have to rely on Rads to heat a poorly insulated home 

The installer came back to check and set everything up for winter 

He asked if we could leave the Rads on for a few hours 

All in all we are pleasantly surprised at how straightforward a HP is and hot water on tap 24-7 is a bonus 

 

I don’t get the heat pump and rads comments I could run a heat pump instead of a boiler with the same flow temps

 

I’m running a gas boiler 13 rads with a flow temp of 30 - to 40 deg depending on outside temp - it’s an early 1980’s with some insulation improvements (loft insulation is mainly 70mm so sub standard) and I’m running it 24/7 with setbacks at night and during the day when there is no one home - rad delta is around 6 to 9 deg (depending on flow temp) none of the rads are in the traditional sense hot but room temps are comfortable.

[ReedRichards]

23 hours ago, marshian said:

I’m running a gas boiler 13 rads with a flow temp of 30 - to 40 deg depending on outside temp

 

Either you have a new installation with a low-temperature gas boiler.  Or you replaced your rads with larger ones at some time in the past.  Or the rads were massively over-specified when they were installed to work with a much higher flow temperature than the 30-40 C you now use

[marshian]

11 hours ago, ReedRichards said:

 

Either you have a new installation with a low-temperature gas boiler.  Or you replaced your rads with larger ones at some time in the past.  Or the rads were massively over-specified when they were installed to work with a much higher flow temperature than the 30-40 C you now use

All of the above 

 

Viessmann 100 W heat only (16 kW)

 

Not a single rad remains from the original house set up 

 

95% of the rads were changed a couple of years ago when I was running a 24kW glow worm boiler 

 

the point I was is that rads correctly sized for flow temps and room demand will work perfectly well whatever the heat source is

[ReedRichards]

1 hour ago, marshian said:

the point I was is that rads correctly sized for flow temps and room demand will work perfectly well whatever the heat source is

 

Hopefully no one is disputing this.  Except possibly @nodwhose earlier comment displayed a lack of understanding.

[SteamyTea]

On 12/12/2024 at 09:26, nod said:

was referring to the temperature of the Rads Warm more than hot

Temperature is not energy, or power.

 

Imagine that you had an equivalent surface area of radiators as an UFH system.

Now while that is often not practical, once you account for floor area that is covered in furniture and rugs, which reduce the power the UFH can deliver, you may find that the areas are not so different.

We should really be calling radiators, UFH and fan assisted, heat or thermal emitters, they all do the same job.

[marshian]

1 hour ago, SteamyTea said:

Temperature is not energy, or power.

 

Imagine that you had an equivalent surface area of radiators as an UFH system.

Now while that is often not practical, once you account for floor area that is covered in furniture and rugs, which reduce the power the UFH can deliver, you may find that the areas are not so different.

We should really be calling radiators, UFH and fan assisted, heat or thermal emitters, they all do the same job.

schedule heating (on/off/on/off) I’m running WC curve of 1.4

 

Constant on (with setback temps instead of off) I’m running a WC curve of 0.8

 

I’m working my way towards on (no setbacks) and I think that will be a WC curve of 0.7

 

Logging HDD data v gas consumption (minus HW) I thing last stage will be 5 to 10% more usage but house comfort will be better (more heat pump like)

 

 

 

[JohnMo]

30 minutes ago, marshian said:

working my way towards on (no setbacks) and I think that will be a WC curve of 0.7

Do you get cycling at low flow temperature? I found when running the boiler at say 36 or below flow temp I would get a 6 to 7 min on 6 mins off cycle. This was quite big gas usage case. Increased the flow temp to 40 and would run without cycling for as long as I wanted. It also dropped gas consumption by a big margin.

[marshian]

7 hours ago, JohnMo said:

Do you get cycling at low flow temperature? I found when running the boiler at say 36 or below flow temp I would get a 6 to 7 min on 6 mins off cycle. This was quite big gas usage case. Increased the flow temp to 40 and would run without cycling for as long as I wanted. It also dropped gas consumption by a big margin.

Yes it cycles more ~32 fires/starts in 24 hr period 

 

with a higher WC and sheduled heating that would be ~12 cycles in 24 hrs

 

however I am not seeing a huge increase in gas consumption with the current boiler (the prev glow worm yes big increase when cycling more than 3 cycles per hour but it had a 10kW min output)

[jayc89]

We were sold a 32kw system boiler before I came across this lovely site. It's now running on weather comp and flow temps don't get much above 50c all year round. We had to upgrade the radiators in a couple of the larger rooms upstairs, they don't get that warm to touch, but still heat the rooms up really well. I wouldn't have much concern going to a HP. 

[marshian]

4 hours ago, jayc89 said:

We were sold a 32kw system boiler before I came across this lovely site. It's now running on weather comp and flow temps don't get much above 50c all year round. We had to upgrade the radiators in a couple of the larger rooms upstairs, they don't get that warm to touch, but still heat the rooms up really well. I wouldn't have much concern going to a HP. 

I’d want to be closer to 40 deg C flow temp to move to a HP - 50 is at the top end of HP range and you might not get the COP you would need to break even on energy cost

(3.0 to 3.5 unless you have a cheaper tariff for electrickery)

 

[jayc89]

1 hour ago, marshian said:

I’d want to be closer to 40 deg C flow temp to move to a HP - 50 is at the top end of HP range and you might not get the COP you would need to break even on energy cost

(3.0 to 3.5 unless you have a cheaper tariff for electrickery)

 

 

Well in a house built in the 1850s, beggars can't be choosers. I'm reasonably happy with the improvements made so far. We still have a few draughts and a couple of rooms to insulate, which might get us to those types of numbers. 

[marshian]

1 hour ago, jayc89 said:

 

Well in a house built in the 1850s, beggars can't be choosers. I'm reasonably happy with the improvements made so far. We still have a few draughts and a couple of rooms to insulate, which might get us to those types of numbers. 

Oooff - you’ve done well in that age building - well done