Heat Pump vs Gas Boiler: Relative Climate Impact

[Green Power]

This will be a comparison of the forecast climate impact of installing heat pump vs gas boiler and then 13 years of use, for the specific case of my house. I'll ignore end of life (disposal) emissions for simplicity: they tend to be small.

I estimate the heat pump at 10.4 tonnes CO2e, the gas boiler at 44.9 tonnes, for a savings of 34.5 tonnes over 13 years.

 

Heat Pump
Operation
2727kWh per year (see my other post "Heat Pump vs Gas Boiler: Lifecycle Cost Comparison" to see how I got this figure) x 0.13kg CO2e/kWh grid carbon intensity = 0.35 tonnes (the assumption on the carbon intensity is UK grid is about 0.20kg/kWH for now, declining steadily to a forecast 0.06kg in 2035, for an average of 0.13 during the period.)
Add on very rough guesstimate 30% to account for emissions in the production and maintenance of the electricity grid and power plants and production of generation equipment = 0.46 tonnes
0.46 tonnes per year for 13 years for a total of 5.99 tonnes over 13 years
Refrigerant
The Dakin model I have uses R32 which has a global warming potential of 675, which means it causes 675 times more warming than the equivalent weight of CO2. To get a CO2 equivalent (CO2e) warming, you can therefore take the 2.2kg of refrigerant and multiply by 675 which gives us 1.49 tonnes of CO2e. I'm guestimating that the refrigerant will leak out completely once during the 13 years, or not be properly disposed of at end of life. (2.2 figure is actually from a Mitshibishi Ecodan, as I couldn't find the figure for my Daikin.)
Manufacture
To work out the climate impact of the production of the heat pump, I estimate 0.35 kg CO2 / £ as a typical carbon intensity of manufactured goods (Mike Berners Lee arrives at this estimate, and I've found it often fits when cross checked against more rigorous studies). So I then apply 0.35 x £8405 which is the full carbon cost of the heat pump installation = 2.94 tonnes.

TOTAL = 10.42 tonnes CO2e. (5.99+1.49+2.94) = 0.80 tonnes CO2 per year.


Gas Boiler
Operation
11588kWh annually (from meter readings) is 2.12 tonnes CO2e per year according to carbonfootprint.com - Home of Carbon Footprinting (it has a converter where you type in the kWh of natural gas and it gives you the CO2).

I´ve added 60% extra (x 1.6) made up of 35% additional for methane leakages (sources and calculation on request) and 25% (a very rough guess) for the other emissions in the supply chain like transport and storage and tankers and building pipelines and operating businesses.

So 2.12 x 1.6 = 3.39 tonnes CO2 per year (2.12 x 1.6) or 44.1 tonnes CO2e over 13 years.
Manufacture
I use 0.35 kg CO2e per £ again x £2300 estimate for a gas boiler and we get 0.8 tonnes CO2e. The reason it's a lot lower than a heat pump is because the heat pump has the hot water tank, the radiators, and a more complex installation which means more labour time which means more economic activity behind that in office and other company emissions.

TOTAL = 44.9 tonnes CO2e (44.1+0.8) = 3.45 tonnes CO2 per year.


Relative Difference
The heat pump is 77% lower overall.
It's an estimated carbon saving of 2.65 tonnes per year.or 34.5 tonnes in total.


Comparison to Other Life Choices
The annual emissions of this heat pump are about the same as the dietary emissions of a vegan growing their own vegetables and composting, whereas the gas boiler is about the same as someone who eats an above average amount of meat with a high food wastage.

A heat pump's annual emissions are similar to an electric car, whereas a gas boiler is similar to a petrol car.

I think a heat pump may be the biggest reduction you can achieve in the UK with a single decision. The reductions are about the same as each of driving an electric car or going vegan or deciding not to fly, but that's only true if you stick to such commitments for a very long time. You may decide to go back to a petrol car, or meat, or flying. In reality, vegetarian meals, not flying etc are a sequence of many decisions. Whereas buying a heat pump locks in savings virtually guaranteed since you are very unlikely to decide to rip it out and go back to a fossil fuel boiler. Those savings are also locked in for your whole family, not just you.

And these numbers are for a 2-bed end terrace at 71 square metres. If you have a large detached house, opportunity for carbon savings will be bigger.

 

Edited November 4, 2022 by Green Power

[nod]

It is just a shame that a heat pumps running costs are so much higher than an efficient gas boiler 

It would also be nice if the power run a HP was greener 

[PeterW]

9 hours ago, Green Power said:

The annual emissions of this heat pump are about the same as the dietary emissions of a vegan growing their own vegetables and composting, whereas the gas boiler is about the same as someone who eats an above average amount of meat with a high food wastage.

A heat pump's annual emissions are similar to an electric car, whereas a gas boiler is similar to a petrol car.

I think a heat pump may be the biggest reduction you can achieve in the UK with a single decision.

I think the term you’re looking for here is greenwashing as those statements are neither linked nor relevant. 
 

9 hours ago, Green Power said:

The reason it's a lot lower than a heat pump is because the heat pump has the hot water tank, the radiators, and a more complex installation which means more labour time which means more economic activity behind that in office and other company emissions.

A boiler also has all these things… and therefore this can be discounted.

 

You ignore end of life recycling in this instance though, and I would also be concerned about the question and quotes on leakage from transmission systems as they are random statements. If you want to make comparisons then they need to be whole life and not just bits you have the data for to illustrate a particular view.

[SteamyTea]

3 minutes ago, PeterW said:

9 hours ago, Green Power said:

The annual emissions of this heat pump are about the same as the dietary emissions of a vegan growing their own vegetables and composting, whereas the gas boiler is about the same as someone who eats an above average amount of meat with a high food wastage.

A heat pump's annual emissions are similar to an electric car, whereas a gas boiler is similar to a petrol car.

I think a heat pump may be the biggest reduction you can achieve in the UK with a single decision.

I think the term you’re looking for here is greenwashing as those statements are neither linked nor relevant. 

Not sure you are right as the title is;

Heat Pump vs Gas Boiler: Relative Climate Impact

 

The link is climate impact.

[PeterW]

8 minutes ago, SteamyTea said:

Not sure you are right as the title is;

Heat Pump vs Gas Boiler: Relative Climate Impact

 

The link is climate impact.

So if I drive a petrol car and I’ve got a heat pump, it becomes neutral..? Or do I need to be vegan to own a petrol car now ..? And what if I own an electric car but an oil boiler ..?

 

My point is that statements such as that above that need to either include whole life emissions or they need to use the same basis and are theoretically modelled or they become pointless. 

[JohnMo]

No the biggest reduction would be better insulated houses. Including your own.

 

Also in your calculations you use the cost of a boiler as £2300, I paid £1000 for mine.  Looking at Screwfix the prices vary from £500, upto about £2500, so you have chosen top end to suit your calculations.

 

If you are looking to retrofit a HP the comparison is do nothing and keep gas (then only gas consumption is included), or replace like with like then a similar gas boiler would be chosen.  

 

Or replace gas with a HP, life style choice, most in this country cannot afford.

[ProDave]

All it shows is using ANY form of heating is going to produce CO2.  There is no neutral option available YET.  That might come, one day, when ALL of our energy is produced by renewable sources, but only then if the CO2 produced actually making the generators can be offset somehow.

 

We need to be honest, stop talking about CO2 neutral, and just talk about doing the best we can to reduce CO2.  People might respond better when real achievable targets are set rather than some theoretical unachievable target that we all know will not happen so why bother trying?

 

In my case I have done that by building a well insulated house that does not need much heat input, installed an ASHP to heat it, and some solar PV for some local renewable generation.  I will probably do more in due course to increase local generation but to do that I will have to either fight stupid rules that limit the amount of PV I can have or just treat them with the contempt they deserve.

[ProDave]

1 minute ago, JohnMo said:

No the biggest reduction would be better insulated houses. Including your own.

No the biggest reduction would be remove yourself from the planet.  But nobody talks about population growth.

[SteamyTea]

37 minutes ago, ProDave said:

nobody talks about population growth

You are right, except you are totally wrong.

 

Thomas Robert Malthus (1766–1834)

 

Club of Rome (1968)

 

Paul Ralph Ehrlich (born May 29, 1932)

 

They are just the well known ones, and they have all been proved wrong.

 

Now distribution of resources is a totally different matter, and this is what you are probably on about, without realising it.

 

Just done a quick calculation, which may be wrong somewhere.

But if we say that a m² of land can produce constant 3W of power, and each person on Earth has access to a mean of 3 kW (currently about 2 kW), then we need an area of 1000 km² to produce that for a population of 9bn people.

So an area the size of France and Spain combined will do it.  But it would, of course, need to be distributed around the globe.  But it is not a huge amount of land and it does not have to be used exclusively for energy production, unlike nuclear and thermal combustion, and to a certain extent hydro.

 

Edited November 5, 2022 by SteamyTea

[JamesPa]

10 hours ago, Green Power said:

I think a heat pump may be the biggest reduction you can achieve in the UK with a single decision.

I have been doing a lot of work on this 'at work' (the scale of our operation is a bit larger than domestic but not so much larger so the same principles apply) and pretty much come to the same conclusion. 

 

Once a building is tolerably insulated (ie do the things that are reasonably practical and reasonably easy given the historical construction - you don't have to aim for passivhaus standards) switching from gas (or resistance electric) to heat pump is definitely the big thing you can do.  We have done this for two of our buildings so far and it reduced the carbon footprint  (based on measured consumption, not just theoretical) of each by a factor of very nearly 4; nothing else we have done has come anywhere close.   Better still the emissions will decrease year on year as the grid decarbonises.  Running costs are about the same (as gas) or better (than resistance electric).  Looked at that way its a bit of a no-brainer, certainly when the plant is due for or nearing renewal.

 

Having said that ProDave is spot on with his comment as well.

25 minutes ago, ProDave said:

No the biggest reduction would be remove yourself from the planet.  But nobody talks about population growth.

 

[SteamyTea]

8 minutes ago, JamesPa said:

(the scale of our operation is a bit larger than domestic but not so much larger so the same principles apply)

The principles apply, but the surface area to volume does not scale in a linear fashion.

8 minutes ago, JamesPa said:

Having said that ProDave is spot on with his comment as well.

Except it is wrong.

[JamesPa]

4 minutes ago, SteamyTea said:

The principles apply, but the surface area to volume does not scale in a linear fashion.

Pretty similar or identical in our case, so not a major influence on the overall conclusion.

 

6 minutes ago, SteamyTea said:

Except it is wrong.

Theoretically, if you only consider energy and envisage a seamless distribution and energy storage system.  But human beings consume materials also and energy storage and or distribution is non-trivial.  I don't think one can logically argue that population growth can be ignored as a factor albeit that it might be politically impossible to affect (so the politicians will instead just let nature take its course, and people will die you unpleasantly as a result of flood or famine rather than not being born as a result of a conscious and planned choice).

[SimonD]

8 minutes ago, JamesPa said:

But human beings consume materials also and energy storage and or distribution is non-trivial. 

 

And I think that is where this debate falls flat. I agree with @PeterW in that unless you consider the whole life-cycle of a product, your calculations about the overall carbon impact of a certain technology are incomplete at best. In addition, you've added 'once insulated' which also supports the assertion that the biggest impact is on reducing energy demand rather than finding a more efficient way to produce heat (and of course you haven't controlled for uninsulated context).

 

As for the wider consideration, just like that ignored with EVs, is the wider environmental impact of large scale deployment of technology. As @SteamyTea alludes to this impact is rarely linear. Considering the installation of one heat pump, it may look simple, but take into considering the additional resources required to build and distribute heatpumps all over the world, just deploying, lets say 1.2 million per year in replacement for gas boilers in the UK, you're look at about 100-120kg per unit extra in steel, about 40kg extra in copper per unit etc. The wider environmental impact of this additional demand, including mining operations and so forth, and you have a significant problem, which will also affect costs where people incorrectly assume they will go down as a result of scaling - with demand on resources likely to increase, they will inevitably go up.

 

Unfortunately, the arguments for/against heatpumps are not simple, nor are they merely at the final user end of the supply chain but it still seems to be a discussion that circles around and around.

[SteamyTea]

13 minutes ago, JamesPa said:

I don't think one can logically argue that population growth can be ignored as a factor

I think you have actually hit the nail on the head.  Except that population is used as a catchall as the problem, not the solution.

I was talking to a St. Agnes resident yesterday about the latest sewage spill.  The problem, according to them, is the increase in housing, and associated people.  I pointed out that, as we were outside of a holiday period, the population was as low as it goes, so that can't be the problem.

I then pointed out that over August Bank holiday, the same thing happened (actually told a well known actor to take his family to another beach).

I also pointed out that the existing sewage system is no 'listed' and could be improved.

So population, time of year is NOT the problem, it is inadequate infrastructure.

Infrastructure is a political issue (may be local or national, but it is a human decision).  Infrastructure costs often seem out of proportion to the local benefits.  Ask each resident of St. Agnes to pay £1000 each to improve the sewage system and you will get a flat 'No Way'.  They think it is the SW Water's job to do it.  They think that SW Water should 'just get on with it'.  So a £10m pound project, that would improve the environment, needs to have the load spread across many people paying, which requires people, lots of people, each paying a little.

If you go back to historical times, villages, small towns and cities were highly polluted and horrible places to live (people moved out in the summer), but by spreading the load nationally, these places became nicer.

So reducing population will only lead to lack of facilities, not better ones.

 

It is all to do with distribution, there are no lack of resources.

[Kelvin]

2 hours ago, ProDave said:

No the biggest reduction would be remove yourself from the planet.  But nobody talks about population growth.

Population growth has been a ‘concern’ for a few hundred years. It was wrong then and it’s still wrong now. It’s the same argument people use when they say the UK is being concreted over when, by any measure, it’s mostly green. The issue isn’t too many people it’s the disproportionate way in which resources are consumed and the amount of waste. The energy crisis is forcing changes to energy usage in a way that no nudge economics policy could ever have achieved. 

[SteamyTea]

3 minutes ago, Kelvin said:

Population growth has been a ‘concern’ for a few hundred years.

I did see something the other day about not having children as we 'inherit' half our children's resource costs.

Not something I subscribe to, except I dislike children, and don't have them.

So inadvertantly saving the planet for further generation of idiots to make mistakes.

[Green Power]

10 hours ago, nod said:

It is just a shame that a heat pumps running costs are so much higher than an efficient gas boiler

Heat pump running costs were discussed on another thread I did, so if anyone is interested we can discuss there.

You are already aware of this other thread of course, but just replying for the benefit of others.

 

 

[Green Power]

9 hours ago, PeterW said:

A boiler also has all these things… and therefore this can be discounted.

 

You ignore end of life recycling in this instance though, and I would also be concerned about the question and quotes on leakage from transmission systems as they are random statements. If you want to make comparisons then they need to be whole life and not just bits you have the data for to illustrate a particular view.

For my specific case, had I installed a boiler no radiators would have been required. Whereas by installing a heat pump a few extra radiators were required, hence further footprint.

 

Had I installed another boiler it likely would have been another combi with no hot water storage tank.

 

I´ve ignored end of life recycling because I´m confident that it is a low % of the total - perhaps 1% or 3% - and therefore won´t affect the total result. The reason I know it´s low is partly because I´ve seen studies and expert opinion over the years that always say this, and partly it´s just common sense. Just think about what goes into taking something to the dump vs all the complex parts of a supply chain to manufacture something.

[PeterW]

4 minutes ago, Green Power said:

Whereas by installing a heat pump a few extra radiators were required, hence further footprint.

 Based on what ..?? A lot of houses have over sized rads to start with - you’d be surprised how little they need increasing especially if you go with the heat pumps with the 48°C flow temps.

 

And you can’t compare a combi to a system boiler - chalk and cheese and also efficiency is wildly different ..!

[Green Power]

9 hours ago, JohnMo said:

No the biggest reduction would be better insulated houses. Including your own.

 

Also in your calculations you use the cost of a boiler as £2300, I paid £1000 for mine.  Looking at Screwfix the prices vary from £500, upto about £2500, so you have chosen top end to suit your calculations.

 

If you are looking to retrofit a HP the comparison is do nothing and keep gas (then only gas consumption is included), or replace like with like then a similar gas boiler would be chosen.  

 

Or replace gas with a HP, life style choice, most in this country cannot afford.

By my calculations the estimated reduction from putting a heat pump in is 77%. And other estimates from others found online have come out similar. There is no way you can reduce your emissions by 77% with insulation. To do that, you would need to be able to reduce your bills by 77% after putting in the insulation, and no one manages that. You can search online for the amount of savings from insulation and it is more in the range of 5% - 30% depending on the type of insulation.

 

There is one area where it might be true and that is new build houses where it is possible to achieve greater reductions with insulation.

 

For the cost of a gas boiler, I think you are referencing my other thread which I linked to above. As I said in that thread, For the price of the boiler, I considered the size of my house and used (I did not get any quotes) How much does a new boiler cost? - Which? (partly paywalled), Guide to New Boiler Installation Costs 2021 and Boiler Calculator - Cost of New Gas Boiler with Installation From the average of these articles I estimate £2,600. However I only paid £1400 for boiler in 2011 (same house), which would be £2000 today with inflation. So I decided to split the difference and call it £2,300.

 

The prices on Screwfix are I assume boilers without installation included which explains why they average nearer to £1000 rather than £2000. My prices (for both boiler and heat pump) include the cost of the installation.

 

For my specific case, the boiler was dying so had I not installed a heat pump I would have had to replace the boiler. So for my case it is relevant to include the emissions of a new boiler in the relative calculation. But if you were considering replacing say a 5-year old gas boiler with a heat pump, then the relative calculations of cost and environmental footprint could of course in such a case exclude the gas boiler`s manufacturer and cost.

Edited November 5, 2022 by Green Power

[Green Power]

13 minutes ago, PeterW said:

 Based on what ..??

This is a case study based on what actually happened in the specific case of my house. The company specifying the heat pump decided to add extra radiators so extra radiators were installed and paid for.

 

I am aware that in some other installations no radiators are added, and that heat pumps can work without additional radiators in many cases.

 

[Dillsue]

8 hours ago, SteamyTea said:

I was talking to a St. Agnes resident yesterday about the latest sewage spill.  The problem, according to them, is the increase in housing, and associated people.  I pointed out that, as we were outside of a holiday period, the population was as low as it goes, so that can't be the problem.

Without knowing the specifics of the spill youre referring to, theres a fair chance the St Agnes resident was partly right in that the surface water from the new housing is helping to inundate the the local sewers when rains heavily. What theyre likely missing is that their surface water is doing the same and would likely cause the same problem without any new housing or holidaymakers.

Everyone turning the shoe on the bottom of their downspouts 90 degrees could likely keep an awful lot of s**t where it belongs.

[Nick Thomas]

1 hour ago, Green Power said:

By my calculations the estimated reduction from putting a heat pump in is 77%. And other estimates from others found online have come out similar. There is no way you can reduce your emissions by 77% with insulation. To do that, you would need to be able to reduce your bills by 77% after putting in the insulation, and no one manages that. You can search online for the amount of savings from insulation and it is more in the range of 5% - 30% depending on the type of insulation.

 

https://journals.sagepub.com/doi/full/10.1177/0143624420975707

 

> A whole house retrofit in-line with current Building Regulations reduces the heating demand and emissions by 65%, and lowers the input electrical demand for the heat pump to under 1 kW

 

Not bad going, honestly.

 

 

[ProDave]

1 hour ago, Nick Thomas said:

 

https://journals.sagepub.com/doi/full/10.1177/0143624420975707

 

> A whole house retrofit in-line with current Building Regulations reduces the heating demand and emissions by 65%, and lowers the input electrical demand for the heat pump to under 1 kW

 

Not bad going, honestly.

 

 

If I read it right, they updated all the insulation levels to meet current building regs requirements, then fitted a heat pump to achieve that 65% reduction?

[PeterW]

5 hours ago, Green Power said:

This is a case study based on what actually happened in the specific case of my house.

But this is a sample of one…. It’s not representative ..!