What is the real story around heat pumps?

[Zero999]

That suggests that either your house is very well insulated (in which case, heat pumps, somewhat unintuitively, indeed often are less advantageous than in less well insulated houses), or you have significant other waste heat sources that keep your house warm (which might be at significant energy costs if it is from electrical devices that could be swapped for more efficient versions), or you like it cool indoors (in which case, you could expect a higher COP from a heat pump).

Both are true. I have my thermostat set to 15°C and my house is very well insulated.

I am assuming that "mild" is around 10°C? That's what we've had here, with the ~ 600% COP I mentioned above.

Yes and my boiler just sits there, so that's irrelevant. It'll probably run a bit at the end of the week when the temperature drops to 5°C.

How did you calculate the future costs of running a gas boiler?

One cannot predict the future. I'm open minded about the possibility of changing, but will stick to what's cheapest for now. I'm willing to listen to rational arguments, but don't take kindly to propaganda and zealotry. I'm well and truly fed up with it from the mainstream media.

Mind you that chances are that you'll have to pay for the damages that your CO2 emissions cause at some point.

Irrelevant, since most of the emissions are from other countries who will not cut them.

I mean, I guess we are getting really off topic here, but ... gold is not a productive asset and therefore not really an investment. It's a speculation vehicle at best.

Gold is a precious metal and is limited in supply, so will only become more valuable over time. The only risk is someone discovers a way to make it cheaply. Given this is highly unlikely, it's certainly a better investment, than an electric heat pump!

b) No, not a gas turbine, but an ordinary, off the shelf, internal combustion engine, similar to the type used to power a small generator and will run off natural gas with only minor modifications. More complicated yes, but not so much as a gas turbine.

But those only have an efficiency of ~ 30%, I think?! Combine that with a COP of 300% and you are at an efficiency of 90%. Of coure, you can then also use the waste heat, but for one that again requires an exhaust heat exchanger (that needs to be cleaned), and also, the overall efficiency still would seem like barely worth the complexity and presumably system cost!?

I thought you said a COP of 600%? Make your mind up!

Natural gas is a clean fuel, so the exhaust won't be any more dirty than my boiler.

Assuming an electric heat pump would give a COP of 300%, a gas one would give a COP of 160% and given gas costs a quarter of the price, it would pay for itself within a few years. An electric heat pump would just cost me more than my current system, both in terms of upfront and running costs. I'm hardly unique. Many others in the UK have found electric heat pumps to be uneconomical here. I'm not against the idea. It just doesn't make any sense, in my situation.

EDIT:
Climate change politics removed.

[Zero999]

Since PV provides a glut of power in summer, recharging is hardly an issue.

It is an issue as there is a relatively short peak power output from solar panels. A common solar panel setup with 12 panels, can deliver around 4kW of output for a couple of hours per day. So either you need a large heatpump capable of taking in 4kW of power and convert this into heat that goes into the ground (assuming the ground can absorb it quick enough) OR have a large battery pack which can smear out putting the energy into the ground over time. Neither is cheap / cost effective. And then you'll still need electricity to get the heat out of the ground again. Where is that coming from? My estimation is that conversion to/from hydrogen (in some form) you can store above ground is more cost effective.

Again with your pushing of solutions and completely ignoring/side stepping the practical ones (pretending like no other options exist).

Oversize the solar array, then it will produce enough energy in winter.

Sure not everyone has the physical space for that, but few have the physical space for ground source thermal storage/dissipation.

You must be joking about over sizing the array for winter. That might work in Australia but would require an huge area in Northern Europe, when there's less than 8 hours' of weak, overcast daylight on the shortest day of the year.

Its an anomaly with the UK at an extreme:
https://www.visualcapitalist.com/mapped-global-energy-prices-by-country-in-2022/

I forgot to say, that link shows gasoline prices. I'm talking about natural gas. I don't know of anyone who uses gasoline to heat their home int the UK. It's very heavily taxed.

FFS, provide in context and relevant data yet the majority that comes back is extraneous dismissals?
That link of the source data has: petrol (gas), electricity, and.... natural gas
The provided plot has electricity and natural gas.
Or is UK petrol 10c/kWh ?

Want to talk about these things, you'd better get your facts barely tested first.

Okay, fair point. I admit, I just looked at the map at the top and didn't read down the page.

[zilp]

I have found options for controlling, or at least read the De Dietrich heat pump with a RS485 interface.

Maybe one thing, for the blue moon.
Do not use RS-485 for long distances, put a converter near the pump, or an isolator.
Yes, it's made for that, but you do not want that the pump side fails.
With luck you have a machine with multiple circuit boards, but it's a monoblock.
With bad luck there's only one PCB and the driver is integrated to MCU.

Often, such a bus in a heating system is intended for the connection to additional components like room thermostats or external mixers or secondary heat sources or what have you, so, while the protocol/data fields might be proprietary, the interface is absolutely expected to be connected outside the heater and thus will usually not be just a bunch of GPIO pins on a connector. Also, the connectors tend to be sturdy stuff (like pluggable 1.5 mm² screw terminals), not pin headers or sume such.

Of course, it's still a good idea to put an isolator between it and any computer you connect to it ...

[Someone]

...
Its an anomaly with the UK at an extreme:
https://www.visualcapitalist.com/mapped-global-energy-prices-by-country-in-2022/
...

That link shows prices as of March '22. Far from reality in Feb 24.

Example of the wide ranging spread of electricity : gas pricing in the real world, so comments from the UK such as gas is 4:1 should be taken with the grain of salt befitting an outlier situation, and not generalised to the rest of the world.

Feel free to put up some more recent figures, or older, or averaged, or whatever. What do you think has changed since those numbers were collected? Over here electricity is cheaper still and gas more expensive, heading further toward a 1:2 ratio.

Prices during a major international upset don't really mean anything about the long term. Some country's energy supplies were disturbed far more than others, so their price rises had a large spread. The chart you posted actually says UK home heating costs were up 3 fold that year. It says 10 cents/kWh for gas. That's less than I have been paying, but its about 3 times what I paid in 2021.

So provide some more appropriate data yourself?

People here are talking about what they pay for energy in its different forms, the relative costs of their energy choices are KEY to this discussion. Yet both sides of the extreme are talking like their situation is completely universal and applies to everyone else. They need to be clearly stating that it is only applicable to their unusual locality and not a general case.

I remember when gas was a 1:4 or 1:5 ratio, but that's not sustainable economically (rationally).  Given the uses of gas a realistic price ratio is heading somewhere closer to 1:2, many countries are already there and betting on cheap gas being either:
a) available in other locations, or
b) continuing the large price ratio into the future
are both unrealistic. But do just argue about any data only being somme single point in time. It's on you to add what you think is constructive rather than trying to claim there is nothing to be gained from the data I have shared.

Plenty of the worlds electricity is tied to gas prices:
https://data.worldbank.org/indicator/EG.ELC.NGAS.ZS
Given the electricity markets and their bidding methods, the most expensive generators are setting the price, often natural gas.

[Zero999]

That seems contradictory? If nuclear is supposedly cheap electricity, then why would the government have to invest in it? Especially when increasing demand is expected with more heat pumps being deployed, why would it need the government to provide the investment for that cheap electricity?

If the goal is to reduce carbon emissions, then investing in nuclear power, so we have cheap electricity, is a no-brainer. Nuclear plants have a high upfront cost, which few private investors are wiling to pay, so it make more sense for the government to invest in it, rather than wasting money on other green schemes such as heat pumps and banning internal combustion engine vehicles. Given cheap, clean, electricity, people will voluntarily switch to heat pumps and electric cars, without subsidies or banning anything. It will also boost the economy, in the form of reduced energy costs to businesses.  Nuclear power will see a return on investment, in the long term.

[Someone]

Your figures for an electric heat pump are wildly optimistic because you used the seasonal average of 350%, when you should use the COP, when it's going to be working hardest and consuming the most power, which will be much lower.

We've been here before again and again.

You can choose to make that analysis on the worst case. But it doesn't make sense unless you have zero cost for your plant, and multiple heating systems installed. That makes sense to almost no-one.

Realistically most people invest/gamble on a single heating source and use the same one all year round. So their fuel costs for the year at SCOP are the correct metric, and depreciation of the plant over its expected life.

[Someone]

The guy who tried to persuade us to buy a oil burner stated that the condensing one, he was going to offer, had an efficiency of 107%. He clearly had no idea what he was talking about.

When i was a kid they advertised a clothes detergent that washed "whiter than white". I'm still scratching my head over that one. I think it may have caused irreparable damage to my mind.

They can be true, many clothes washing detergents/powders add mixtures of fluorescent pigments/dyes which absorb UV and return "white". End result being the clothes washed in that load will be brighter (under sunlight). Same trick is done with expensive paper stock.

Similar sleights of hand are commonplace in discussion of heating/heat-pumps.

[coppice]

Prices during a major international upset don't really mean anything about the long term. Some country's energy supplies were disturbed far more than others, so their price rises had a large spread. The chart you posted actually says UK home heating costs were up 3 fold that year. It says 10 cents/kWh for gas. That's less than I have been paying, but its about 3 times what I paid in 2021.

So provide some more appropriate data yourself?

From my bill from my bill for Dec 2019, just before things started to go weird. Gas was 3.10p per kWh. Electricity was 14.35p per kWh. Those prices are from a single integrated energy bill. That's about in line with the actual cost of provision. Have you looked at how much of your electricity bill goes to pay for the fuel? UK bills used to have the fuel component broken out from the cost of running the grid. The fuel wasn't that big a part.

[Someone]

Surface area is the key, although the ground looks like an infinite heatsink to a single user with a very slow time constant, over human time scales and densities it doesn't work without active recharging:

Though, recharging is absolutely utterly trivial. For some weird reason, it is usually not being done; people invest 20-25k€ on a system which misses a simple opportunity which costs a few hundred extra. I think it's chicken and egg problem; people don't understand the need, thus no one asks for it, thus it's not provided, thus it's weird custom work and therefore expensive if possible at all.

As long as the drill hole is correctly dimensioned, it all works out. But underdimensioned systems are surprisingly common here, like you pay 25k€ for the expensive heatpump itself + to get the boring equipment at your place and drill 155 meters as miscalculated by sales people trying to pinch the last penny, when you could pay maybe 500€ extra for 20-30 meters deeper. And/or 500€ extra for a turnover valve plus something which resembles car radiator, for summertime charging.

As discussed in that other linked thread. Ground source works well if you have sole access to the resource or don't care about 20+ years into the future.

It's that 100mW/m2 replacement rate thing, which happens to be close to 1kWh per year per m2 of land area. For the OP who's wanting 16500kWh annually and very little air conditioning, that's a massive sized block needed to be sustainable! Or they should factor in some energy for replenishing the ground source which is additional expense again.

[Someone]

Prices during a major international upset don't really mean anything about the long term. Some country's energy supplies were disturbed far more than others, so their price rises had a large spread. The chart you posted actually says UK home heating costs were up 3 fold that year. It says 10 cents/kWh for gas. That's less than I have been paying, but its about 3 times what I paid in 2021.

So provide some more appropriate data yourself?

From my bill from my bill for Dec 2019, just before things started to go weird. Gas was 3.10p per kWh. Electricity was 14.35p per kWh. Those prices are from a single integrated energy bill. That's about in line with the actual cost of provision. Have you looked at how much of your electricity bill goes to pay for the fuel? UK bills used to have the fuel component broken out from the cost of running the grid. The fuel wasn't that big a part.

Learn how wholesale electricity is priced. They don't run fixed margins or simple input costings.

Also, you can keep pointing to UK examples. That's my point that I keep pushing. Hold onto them for dear life and enjoy that distorted market. It won't last, and it's just a UK thing. The rest of the world is not getting those huge price differentials.

[coppice]

It's that 100mW/m2 replacement rate thing, which happens to be close to 1kWh per year per m2 of land area.

The replacement rate is all over the place, depending on the kind of land you are on. Its seldom very high, but trying to use a single figure doesn't make a lot of sense.

[Someone]

It's that 100mW/m2 replacement rate thing, which happens to be close to 1kWh per year per m2 of land area.

The replacement rate is all over the place, depending on the kind of land you are on. Its seldom very high, but trying to use a single figure doesn't make a lot of sense.

It makes a lot of sense when that figure is applicable (within +/-50%) to the vast majority of people). Well done distracting people on a small discrepancy when the discussion is about people pulling several orders of magnitude more than the sustainable rates.

but but but something is a factor of 2 out....
don't mean squat when the problem is a factor of 1000

[coppice]

Also, you can keep pointing to UK examples. That's my point that I keep pushing. Hold onto them for dear life and enjoy that distorted market. It won't last, and it's just a UK thing. The rest of the world is not getting those huge price differentials.

I point to UK examples as I know how things have been here for half a century, so I have a long term view. Since a pipeline network brought natural gas to our homes in the late 1960s it has been a small fraction of the cost of coal or electric heating, and considerably cheaper than oil, which people in the countryside still have to use.

[coppice]

It's that 100mW/m2 replacement rate thing, which happens to be close to 1kWh per year per m2 of land area.

The replacement rate is all over the place, depending on the kind of land you are on. Its seldom very high, but trying to use a single figure doesn't make a lot of sense.

It makes a lot of sense when that figure is applicable (within +/-50%) to the vast majority of people). Well done distracting people on a small discrepancy when the discussion is about people pulling several orders of magnitude more than the sustainable rates.

but but but something is a factor of 2 out....
don't mean squat when the problem is a factor of 1000

You know some people have water flows through the soil below their homes that gives them a rapid replacement of harvested energy. It really is a wide range.

[Someone]

It's that 100mW/m2 replacement rate thing, which happens to be close to 1kWh per year per m2 of land area.

The replacement rate is all over the place, depending on the kind of land you are on. Its seldom very high, but trying to use a single figure doesn't make a lot of sense.

It makes a lot of sense when that figure is applicable (within +/-50%) to the vast majority of people). Well done distracting people on a small discrepancy when the discussion is about people pulling several orders of magnitude more than the sustainable rates.

but but but something is a factor of 2 out....
don't mean squat when the problem is a factor of 1000

You know some people have water flows through the soil below their homes that gives them a rapid replacement of harvested energy. It really is a wide range.

And like your unicorn pricing for gas in the UK, that's the unusual/exceptional case.

Why keep coming in and arguing I cant discuss typical/average figures? (as I'm happy to explain and frame them as such).

You're being misleading and adding noise by jumping to the extremes as some alleged examples, but without actually saying that they are extremely specific/unusual. Things need to be explained in context, not just short "look at me" technically true by omission rubbish.

Why keep coming back and trying to cut down the typical/reasonable/supported positions? It's trivial to point out you're just using extreme cases.

[zilp]

It's nonsense because China, Russia and the USA are never going to adopt net zero.

Why not?

The UK's emissions are truly tiny. It won't make any difference on a global scale, whilst having a huge impact on our economy. What's worse is many of our emissions are being outsourced to other countries, which has the effect of increasing them, as goods require shipping.

That sounds like you need a border adjustment tax?

How did you calculate the future costs of running a gas boiler?

One cannot predict the future.

Why not?

I'm open minded about the possibility of changing, but will stick to what's cheapest for now. I'm willing to listen to rational arguments, but don't take kindly to propaganda and zealotry. I'm well and truly fed up with it from the mainstream media.

Do I smell propaganda at work?

Mind you that chances are that you'll have to pay for the damages that your CO2 emissions cause at some point.

Irrelevant, since most of the emissions are from other countries who will not cut them.

How is that a relevant response? If you have to pay for the damages, that doesn't get cheaper even if it is true that most of the emissions are from other countries who will not cut them, does it?

I mean, I guess we are getting really off topic here, but ... gold is not a productive asset and therefore not really an investment. It's a speculation vehicle at best.

Gold is a precious metal and is limited in supply, so will only become more valuable over time. The only risk is someone discovers a way to make it cheaply.

No, that doesn't follow. And really, I smell propaganda that has convinced you of such nonsense in order to sell you gold, using your rudimentary understandig of economics and your distrust of "main stream whatever" to turn you into a mark for someone's scam.

Price results from supply *and* demand. Limited supply with decreasing demand still leads to decreasing prices. As the majority of gold demand is from speculators, there is no fundamental reason why demand couldn't decrease (as opposed to technical uses, say, where the practical value of the products that contain gold and where gold is hard to substitute drive the demand). Really, what keeps the value of gold up is exactly such marketing campaigns that mislead people who lack deeper economical understanding into "investing" in it, because that is what generates the demand.

If you buy gold, that's a bet on other people buying gold, and them doing so at a higher rate than gold is supplied to the market, so that you can later sell it to them. That's it.

Which is in contrast to investment, i.e., putting your financial resources into things that produce other things of value. Like, if you buy a (share of a) company that owns a machine that makes bread, where the machine making bread produces value (because of the value of bread for people's survival that people are willing to pay for) that you get a share of.

Given this is highly unlikely, it's certainly a better investment, than an electric heat pump!

Well, no. It certainly has a different risk profile, but it is in no way obvious that putting your money into gold would have a higher return than putting it into a heat pump over the lifetime of the heat pump. Though maybe things are different for you personally, given that you seem to use very little heating anyway. But then again, possibly a simple, relatively low-power air to air heat pump could actually work for you, and those can often be had relatively cheaply.

But those only have an efficiency of ~ 30%, I think?! Combine that with a COP of 300% and you are at an efficiency of 90%. Of coure, you can then also use the waste heat, but for one that again requires an exhaust heat exchanger (that needs to be cleaned), and also, the overall efficiency still would seem like barely worth the complexity and presumably system cost!?

I thought you said a COP of 600%? Make your mind up!

There is no need to make up my mind, you just have to pay attention.

I am *currently* (as in: most of February so far) heating with a COP of around 600%. As in: Right now, my heat pump draws 476 W electric (pumps and everything included) and outputs 2786 W of heat, so 2786 W / 476 W = 585 % COP.

Which I mentioned above to explain why an average of 350% is reasonable, even though the COP can be lower during really cold days.

To compare heating systems, you obviously have to use annual averages, and that certainly is not 600%.

And also, I used the 300% because that was the number that you used in the post that I was replying to.

Natural gas is a clean fuel, so the exhaust won't be any more dirty than my boiler.

Well, it is clean in comparison to other fuels. But it is not clean as in "doesn't leave any residue". Whether it would be dirtier than your boiler isn't really that easy to say, as the dirt that results from the combustion really depends on the conditions.

Assuming an electric heat pump would give a COP of 300%, a gas one would give a COP of 160%

How did you get to that number?

and given gas costs a quarter of the price, it would pay for itself within a few years.

What price are you assuming for a gas-driven heat pump, and how did you arrive at it?

I have no idea what they cost, but I would expect them to be even more expensive than electrically driven ones as they are more complex to build (combustion engine vs. electric motor) and more difficult to install (need a gas line i addition to electricity and potentially refrigerant lines)!?

[coppice]

It's that 100mW/m2 replacement rate thing, which happens to be close to 1kWh per year per m2 of land area.

The replacement rate is all over the place, depending on the kind of land you are on. Its seldom very high, but trying to use a single figure doesn't make a lot of sense.

It makes a lot of sense when that figure is applicable (within +/-50%) to the vast majority of people). Well done distracting people on a small discrepancy when the discussion is about people pulling several orders of magnitude more than the sustainable rates.

but but but something is a factor of 2 out....
don't mean squat when the problem is a factor of 1000

You know some people have water flows through the soil below their homes that gives them a rapid replacement of harvested energy. It really is a wide range.

And like your unicorn pricing for gas in the UK, that's the unusual/exceptional case.

Why keep coming in and arguing I cant discuss typical/average figures? (as I'm happy to explain and frame them as such).

You're being misleading and adding noise by jumping to the extremes as some alleged examples, but without actually saying that they are extremely specific/unusual. Things need to be explained in context, not just short "look at me" technically true by omission rubbish.

Why keep coming back and trying to cut down the typical/reasonable/supported positions? It's trivial to point out you're just using extreme cases.

Its not that rare. Certainly ground sourcing has problems for most people, but there is a significant pool of people on suitable for whom ground sourcing seems like a solid long term solution. For keeping a home comfortable there is no one size fits all solution.

So, what are the kWh prices from your energy bills pre-COVID and Ukraine war? Have the long term trends for their ratio been steady? When the UK started running low on gas from the North Sea a lot of us assumed heating costs would rapidly rise, but they didn't until the recent troubles. I wouldn't call prices sustained for decades as unicorn prices. Your point about wholesale electricity prices misses the point. Those are the prices the grid pays the producers. The prices the grid charges end users have to add a lot of the grid costs onto the wholesale prices, and they are not small.

[themadhippy]

The prices the grid charges end users have to add a lot of the grid costs onto the wholesale prices

Arent  those cost  what the standing charge is meant to cover

[coppice]

The prices the grid charges end users have to add a lot of the grid costs onto the wholesale prices

Arent  those cost  what the standing charge is meant to cover

That is a contribution to grid maintenance when you are connected but not consuming (i.e. nobody at home). Its not the full grid cost. The huge costs of maintaining a grid are what made the people in the 1950s who said cheap sources (mostly nuclear) could make electricity too cheap to bother metering so obviously clueless.

[Someone]

When the UK started running low on gas from the North Sea a lot of us assumed heating costs would rapidly rise, but they didn't until the recent troubles. I wouldn't call prices sustained for decades as unicorn prices.

This is a worldwide forum, with an OP asking about merits on mainland Europe. So yes, UK pricing is a minority viewpoint/effect, and being a massive outlier in pricing while being a small market make that a unicorn. I put up the evidence and links to source material for those claims.

Your point about wholesale electricity prices misses the point. Those are the prices the grid pays the producers.

You said fuel prices don't make a substantial dent in your overall energy bill.
a) that's for fuel in this corner case of the UK market
b) that's averaged across the year and generation mix (unstated)
c) how the fuel cost contributes to the consumer electricity price is unlikely to add only to that "portion" of the bill as presented to you

I was commenting on your overly simplistic view of energy pricing, which you're doubling down on. Keep talking about the UK as if its some universal truth applicable to the rest of the world and you'll keep getting the same response.....

[Someone]

You know some people have water flows through the soil below their homes that gives them a rapid replacement of harvested energy. It really is a wide range.

And like your unicorn pricing for gas in the UK, that's the unusual/exceptional case.

Why keep coming in and arguing I cant discuss typical/average figures? (as I'm happy to explain and frame them as such).

It's not that rare. Certainly ground sourcing has problems for most people, but there is a significant pool of people on suitable for whom ground sourcing seems like a solid long term solution.

Says you citation required.

Or are you moving the goalposts? From the thermal resource available to people is generally much higher than 100mW/m2, to that doesn't actually matter because most people will recharge the resource?

You're just throwing out argument for noise at this point when you cant even be clear what it is you are claiming.

[tszaboo]

Something else I just looked up. An Air source heatpumps uses something like 25KG of copper. So our entire copper reserves worldwide are only enough for 45 million heatpumps if we use all of it for that, which is about the number of households in Germany  .Geothermal uses that as well. I guess it's also time probably to use Aluminium for these, otherwise the great plans might be in peril.

That can't be right. There's already more than 25 kilos of copper piping in most central heating systems.

I think it's just the outside heat exchanger that has that much copper. Anyway, double checking it my math is off by a magnitude or so. It didn't make sense after reading it again.

Again with your pushing of solutions and completely ignoring/side stepping the practical ones (pretending like no other options exist).

Oversize the solar array, then it will produce enough energy in winter.

Sure not everyone has the physical space for that, but few have the physical space for ground source thermal storage/dissipation.

Almost nobody has place for that here. I have a system that covers my yearly electricity consumption, in fact makes an extra MWh. And I needed 5 GJ heat this december, which is 1400KWh, while my solar made 52KWh, which is a factor of 27. Even with SCOP of 5, it's just not going to be worth it to install 6x the solar on my roof, no space, no money for it.

[zilp]

That seems contradictory? If nuclear is supposedly cheap electricity, then why would the government have to invest in it? Especially when increasing demand is expected with more heat pumps being deployed, why would it need the government to provide the investment for that cheap electricity?

If the goal is to reduce carbon emissions, then investing in nuclear power, so we have cheap electricity, is a no-brainer. Nuclear plants have a high upfront cost, which few private investors are wiling to pay,

Hu? Where did you get the idea that few private investors are willing to pay high upfront costs with almost guaranteed returns?! I mean, unless you mean "few" as in "most individual people don't have the money to pay for a nuclear power plant"?! I mean, BlackRock have 9 trillion USD of assets under management ... they certainly could find a bunch of people among their clients who would have the cash to build a nuclear power plant and would be willing to do so for reliable returns!? Sounds almost ideal for pension funds! And they obviously aren't the only large asset managers out there.

My best guess is that what you've heard is that few private investors are willing to fund high upfront costs with significant risks. Like, funding billions for medical research where there is a significant chance that nothing comes of it. Which is true. But that is because of the risk, not because of the high costs. And if there is significant risk, then that is exactly the contradiction that I was talking about: How can a nuclear power plant be both a reliable cheap source of electricity (which thus would have reliable long-term returns, if you own the power plant that can produce power cheaper than everyone else) and at the same time a high-risk investment that would need the government to step up?

so it make more sense for the government to invest in it, rather than wasting money on other green schemes such as heat pumps and banning internal combustion engine vehicles.

Why do you think that that is wasting money?

Given cheap, clean, electricity, people will voluntarily switch to heat pumps and electric cars, without subsidies or banning anything. It will also boost the economy, in the form of reduced energy costs to businesses.

Well, that much is obvious, yeah.

Nuclear power will see a return on investment, in the long term.

That part though ... your arguments certainly don't support that conclusion.

[tom66]

Your figures for an electric heat pump are wildly optimistic because you used the seasonal average of 350%, when you should use the COP, when it's going to be working hardest and consuming the most power, which will be much lower.

A heat pump may drop in efficiency as load increases and temperature falls, but so does a boiler.  The headline efficiency of 85-90% is only achieved at the point where the return water is below 40C.  Once you demand higher load from a boiler and need a flow of 70-75C, efficiency falls as far down as 70%.  Meanwhile a heat pump will still be achieving a COP around 300%. 

How does the efficiency of a gas boiler drop with temperature? The reverse is true because more heat is extracted from the water being pumped through the radiators. It's more efficient for a gas boiler to heat the water from 25°C to 75°C, than it is for it to heat from 55°C to 75°C. The opposite is true for heat pumps, which need the water to be as lower temperature as possible, hence large pipes and massive radiators, and the COP drops, with the outside temperature.

Unfortunately, it does.  Because condensing boilers don't condense when the return temperature is above 45-50C (roughly). Typically the radiator loop on your system might lose 20-25C between flow and return, but if your radiators are sized so that it can only be properly heated when the flow output temperature is >60C then it will suffer from reduced efficiency in cold weather.  This is currently the case for our house, and it's sadly very common as heating engineers aren't physicists, they just know that they need so many kW per m^2 so install the smallest radiators they can get away with.

When a boiler doesn't condense, the exhaust ends up with plenty of waste heat in it, which isn't heating your property.  Combi boilers also do not condense when providing hot water, as there is no return path.

No such issue occurs for a boiler that is non-condensing, those are rare (especially today) and just generally have all-round bad efficiency.

I question your figure of a COP of 300%. I only use my heating when it's properly cold. It's been mild for the last week or so and my gas boiler has sat idle. 300% seems optimistic, given it'll get used when the temperature outside is close to or below freezing. Even then a COP of 300% is no good, unless the price of electricity were to fall significantly.

A property in the UK will only be approved for the grant when a COP of at least 280% is achieved.   Octopus only install systems >330% COP.  One can surmise from this is most systems installed under the MCS scheme will have a COP of 300% or above.  Octopus are the largest installer of these systems.

You are not the only user of heating systems so I couldn't comment on whether your scenario is going to achieve worse efficiency or not... but it's probably not relevant to the overall economics of heat pumps, most around here use their heating for at least 4-5 months of the year.  It's pretty easy to see the boiler vents on a cold day after all.

[Someone]

Again with your pushing of solutions and completely ignoring/side stepping the practical ones (pretending like no other options exist).

Oversize the solar array, then it will produce enough energy in winter.

Sure not everyone has the physical space for that, but few have the physical space for ground source thermal storage/dissipation.

Almost nobody has place for that here. I have a system that covers my yearly electricity consumption, in fact makes an extra MWh. And I needed 5 GJ heat this december, which is 1400KWh, while my solar made 52KWh, which is a factor of 27. Even with SCOP of 5, it's just not going to be worth it to install 6x the solar on my roof, no space, no money for it.

Which you know... I said (and you quoted). The size of that setup is comparable to the sustainable footprint ground source heating in those cold places where little to no air-conditioning is needed (and solar production falls way off in winter).

Why go straight to extremes with a pure solar setup? its a convenient strawman? Energy supply is almost always cheapest as a mix of things.

Sizing solar arrays to the inverter or export limit is old thinking. Panels are cheap and adding more capacity (vertical for winter production for example) can be cost effective for many.

Also to be pedantic you don't need 5 GJ of energy for heating, you want 5 GJ of energy for heating. That's a choice and how you supply it is up to you (and you can pay for it).