How viable is electric heating in the UK?

[Bletchleyite]

Moderator note: split from

Do you think that the UK switching to electric vehicles is realistic?

Given the significant obstacles involved with using electric cars and the massive change in infrastructure that would be required do you think it’s practical. I’m especially thinking of those that live in blocks of flats that have no choice but to park on the street or those who do long...

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It is also likely that EV charging will totally collapse the Economy 7 mechanism because summer peak electricity demand will shift to night time.

So? Storage heaters are "on the out" anyway, heat pumps are more efficient. They're rubbish anyway.

If there are places where they're applicable, improved electronic control systems could charge them up in periods of lower demand, whenever those periods might occur (same for the car).

 

[HSTEd]

So? Storage heaters are "on the out" anyway, heat pumps are more efficient. They're rubbish anyway.

I actually debate this point with various colleagues even now!

It is not at all clear that, on a system basis, heat pumps are actually dramatically superior to storage heating / hot water cylinders.

Indeed in a rapid decarbonisation situation they may be substantially inferior.
But we could have a whole thread on just that!

 

[Bletchleyite]

I actually debate this point with various colleagues even now!

It is not at all clear that, on a system basis, heat pumps are actually dramatically superior to storage heating / hot water cylinders.

Indeed in a rapid decarbonisation situation they may be substantially inferior.
But we could have a whole thread on just that!

Anything is superior to a heating system where you have to decide if you want the heating on or not the day before. Awful things. Have you ever lived in a place that had them?

(Overnight heating of a well insulated hot water cylinder is a bit different, as you will pretty much always want that)

 

[HSTEd]

Anything is superior to a heating system where you have to decide if you want the heating on or not the day before. Awful things. Have you ever lived in a place that had them?

Well modern storage heaters are a lot better than the 80s ones, major advances in insulation technology have seen to that.

My experience is very few people make short term adjustments to their heating solution most of the time, apart from maybe "hour boost" buttons. They set it on the heating season and then thats that.


Given the realities of the heating demand curve and various price collapse related phenomena it is quite possible that storage heaters will come out as the cheapest way to heat a housing unit.

Indeed some rapid decarbonisation scenarios instantanoeus resistive heating can still beat heat pumps in economic terms.

EDIT:

Also the reality of heat pump systems is you can't make short term heating decisions - they are either on or not because they ahve such low peak outputs, it takes hours to reach equilibrium
And I think we should create a new thread to avoid derailling this one maybe?

EDIT #2:

There is also the solution of a storage heater that is a big tank of hot water that plumbs into existing heating systems.

 

[stuu]

Well modern storage heaters are a lot better than the 80s ones, major advances in insulation technology have seen to that.

My experience is very few people make short term adjustments to their heating solution most of the time, apart from maybe "hour boost" buttons. They set it on the heating season and then thats that.

Storage heaters are appalling! My previous flat was ~10 years old so well insulated and had storage heaters as it's main heating. In the winter, this meant putting them up very high in order for the flat to be warm in the evening. The downside was that it was like being in the Sahara in the mornings, so I had to open windows to let out the heat in the morning, which is an absolute waste of money. Added to which I was at work so didn't need the heat anyway. Although to be fair it meant that during lockdowns and working from home my heating costs didn't change, but that's not really an argument for the stupid things

With central heating with a thermostat, this problem does not arise, so of course people don't need to make regular adjustments

 

[rangersac]

Well modern storage heaters are a lot better than the 80s ones, major advances in insulation technology have seen to that.

My experience is very few people make short term adjustments to their heating solution most of the time, apart from maybe "hour boost" buttons. They set it on the heating season and then thats that.


Given the realities of the heating demand curve and various price collapse related phenomena it is quite possible that storage heaters will come out as the cheapest way to heat a housing unit.

Indeed some rapid decarbonisation scenarios instantanoeus resistive heating can still beat heat pumps in economic terms.

EDIT:

Also the reality of heat pump systems is you can't make short term heating decisions - they are either on or not because they ahve such low peak outputs, it takes hours to reach equilibrium
And I think we should create a new thread to avoid derailling this one maybe?

EDIT #2:

There is also the solution of a storage heater that is a big tank of hot water that plumbs into existing heating systems.

I do have to ask, have you ever used a heat pump? Unless it's inappropriately sized for the space it's trying to heat, they work faster than any resistive or hydronic systems I have used. And having lived on the west coast of Scotland with a coal fired back boiler as my only heat source at one point I know what I'd prefer!

 

[HSTEd]

I do have to ask, have you ever used a heat pump? Unless it's inappropriately sized for the space it's trying to heat, they work faster than any resistive or hydronic systems I have used. And having lived on the west coast of Scotland with a coal fired back boiler as my only heat source at one point I know what I'd prefer!

I have never had one personally, but I have known several people who have them and I've also seen the stats on heat pump use in housing.

The real problem is the huge capital costs of installation [in non monetary terms] of these systems.
[The mooted required for massive insulation retrofit that is often cited doesn't help either]

The real problem is that given industrial mobilisation constraints, it would be better to just install resitive heating of whatever type (be it storage heaters, hot water heat storage or instantaneous heating) and spend the resources and manpower obtaining additional zero carbon electricity instead of fitting the heat pumps/insulation/whatever.

If we went straight for straight resistive heating we would need about ~200GWe of nuclear or 357GWe of offshore wind to supply our demand, which is alot but even with a heating system far more efficient than heat pumps can ever dream [magical universal district heating] that figure still only drops to 150GWe/255GWe because of all other energy demands in the system. We are also not short of dump/controllable loads because of the huge hydrogen requirements for plastics chemicals, aviation fuel and maritime shipping fuels.

So 28 million retrofit heat pumps in every property saves less than 50/102GWe of nuclear/offshore respectively.
28 million heat pump installations or 34 ABWR type nuclear reactors, or ~7,300 additional Haliade-X class wind turbines.

The latter two are far more amenable to mass production!

== Doublepost prevention - post automatically merged: 20 Jun 2022 ==

Storage heaters are appalling! My previous flat was ~10 years old so well insulated and had storage heaters as it's main heating. In the winter, this meant putting them up very high in order for the flat to be warm in the evening. The downside was that it was like being in the Sahara in the mornings, so I had to open windows to let out the heat in the morning, which is an absolute waste of money. Added to which I was at work so didn't need the heat anyway. Although to be fair it meant that during lockdowns and working from home my heating costs didn't change, but that's not really an argument for the stupid things

With central heating with a thermostat, this problem does not arise, so of course people don't need to make regular adjustments

New-style forced air storage heaters or hot-water heat stores are much better in this respect, since they have much better control of when heat leaves the store. But the fact is even instantaneous heating systems are likely preferable in industrial mobilisation terms.

 

[rangersac]

I have never had one personally, but I have known several people who have them and I've also seen the stats on heat pump use in housing.

The real problem is the huge capital costs of installation [in non monetary terms] of these systems.
[The mooted required for massive insulation retrofit that is often cited doesn't help either]

The real problem is that given industrial mobilisation constraints, it would be better to just install resitive heating of whatever type (be it storage heaters, hot water heat storage or instantaneous heating) and spend the resources and manpower obtaining additional zero carbon electricity instead of fitting the heat pumps/insulation/whatever.

If we went straight for straight resistive heating we would need about ~200GWe of nuclear or 357GWe of offshore wind to supply our demand, which is alot but even with a heating system far more efficient than heat pumps can ever dream [magical universal district heating] that figure still only drops to 150GWe/255GWe because of all other energy demands in the system. We are also not short of dump/controllable loads because of the huge hydrogen requirements for plastics chemicals, aviation fuel and maritime shipping fuels.

So 28 million retrofit heat pumps in every property saves less than 50/102GWe of nuclear/offshore respectively.
28 million heat pump installations or 34 ABWR type nuclear reactors, or ~7,300 additional Haliade-X class wind turbines.

The latter two are far more amenable to mass production!

== Doublepost prevention - post automatically merged: 20 Jun 2022 ==


New-style forced air storage heaters or hot-water heat stores are much better in this respect, since they have much better control of when heat leaves the store. But the fact is even instantaneous heating systems are likely preferable in industrial mobilisation terms.

I don't follow your logic of "The real problem is that given industrial mobilisation constraints, it would be better to just install resitive heating of whatever type (be it storage heaters, hot water heat storage or instantaneous heating) and spend the resources and manpower obtaining additional zero carbon electricity instead of fitting the heat pumps/insulation/whatever." There's minimal difference in labour costs to installing a bunch of storage heaters in a house as opposed to a heat pump. And if you are fitting resistive heaters to many rooms in a house I fail to see what the difference is in non monetary capital costs is between installing several of these units and what is basically one big fridge compressor unit and some ducting. Also the good thing about heat pumps is for houses with hydronic heating/ hot water setups powered by a combi boiler (which I would say is quite a significant portion of UK housing stock although I don't have stats to hand) is that you can retrofit these with a suitable sized heat pump hot water unit.

 

[HSTEd]

I don't follow your logic of "The real problem is that given industrial mobilisation constraints, it would be better to just install resitive heating of whatever type (be it storage heaters, hot water heat storage or instantaneous heating) and spend the resources and manpower obtaining additional zero carbon electricity instead of fitting the heat pumps/insulation/whatever." There's minimal difference in labour costs to installing a bunch of storage heaters in a house as opposed to a heat pump. And if you are fitting resistive heaters to many rooms in a house I fail to see what the difference is in non monetary capital costs is between installing several of these units and what is basically one big fridge compressor unit and some ducting. Also the good thing about heat pumps is for houses with hydronic heating/ hot water setups powered by a combi boiler (which I would say is quite a significant portion of UK housing stock although I don't have stats to hand) is that you can retrofit these with a suitable sized heat pump hot water unit.

Heat pump installations cost many thousands of pounds due to the high price of equipment and the complex installation, normally involving air ducting or replacing all the radiators in a house to achieve the necessary outputs with much lower loop temperatures. There is substantial plumbing work, installation and testing.
A storage heater installation costs taking the old radiators off the wall [which you will likely have to do either way] and replacing them with storage heaters, then pulling wiring. And you are done.

The former consumes far more in terms of specialist labour-hours than the storage heater solution, where only the final wiring and test requires specialist skills.

Same for instantaneous electric heaters where American style baseboard heaters are even easier to install! And that's if you don't just have a drop in electric boiler.
And if you try to install a forced air system you are probably going to have to rip half the house apart to get it in.

In this future energy system the storage heaters also have to have rather less storages than has been historically normal because we are more interested in "notching" power demand by not using power at certain times of day, rather than only using power a small fraction of the time as is traditional. In the limiting case of an all nuclear fleet the size of the storage heaters is reduced by a factor of six. A 21kWh/3kW storage heater is replaced with a ~3.5kWh/1kW heater because the heating element is running a very large fraction of the time

It's actually small enough storage that a ~200L hot water cylinder with a pair of 3kW immersion heaters is almost suitable for a whole house, and it could be fitted with few changes to the bulk of an existing wet heating system.

 

[rangersac]

OK, so you are now talking about monetary costs, not non-monetary ones. And yes you are correct, heat pumps do have a large initial cost but are much cheaper to run than resistive systems, and I think you overstate the complexity of heat pump installation requirements, as this entirely depends on the size required and how the heat is distributed.

A simple heat pump installation is far from complex, it's an external unit on a frame with a power source and a loop to an internal unit which has much more flexibility in terms of location (wall, floor, kickboard, ceiling) than a storage unit. A single unit is easily installed in a day, it's where ducting gets involved that it can take time. If there's an existing hydronic system, installing larger radiators is no more labour intensive than removing old ones and all of the associated plumbing and putting in storage heaters in their place (not to mention potentially far less messy in terms of having to repaint skirting etc).

As for forced air systems, provided there's underfloor or ceiling/ loft space, they are very easy to install. It's only in large houses where you require distributors that it gets more complex. I have personally installed a ceiling located heat transfer kit (noting I am not a tradie here) which was nothing more than a low power impeller fan, a inlet duct where the main heat source was located (lounge area), and outlets to three bedrooms at the other end of the house, which adequately kept the adjacent corridor/ bathroom areas warm as well. The full kit was around 500 quid from memory, and whilst it took me several hours (the roof space was rather cosy), I'm sure someone who knew what they were doing could've probably done it in two or three.

 

[StKeverne1497]

[...]

In this future energy system the storage heaters also have to have rather less storages than has been historically normal because we are more interested in "notching" power demand by not using power at certain times of day, rather than only using power a small fraction of the time as is traditional. In the limiting case of an all nuclear fleet the size of the storage heaters is reduced by a factor of six. A 21kWh/3kW storage heater is replaced with a ~3.5kWh/1kW heater because the heating element is running a very large fraction of the time

It's actually small enough storage that a ~200L hot water cylinder with a pair of 3kW immersion heaters is almost suitable for a whole house, and it could be fitted with few changes to the bulk of an existing wet heating system.

Well, your "limiting case" isn't terribly likely in practice, is it? Therefore instead of a small heater running constantly (which is actually better for comfort, given that heat losses are fairly constant too), a larger heater is needed which runs when necessary and if this is to be used in some kind of balancing mechanism then storage is almost mandated so that you don't end up heating the house at 3am when you're tucked up in bed, or at 11am when you are just boiling the kettle in the staff canteen.

Same goes for hot water. We have a 370l storage cylinder which spent its first year being charged entirely by 2× 3kW immersions - as high as 70C because hot water (DHW) is extracted via a heat exchanger and the hotter you store the water, the more energy is stored. Now, granted we also run the radiators from this cylinder and we're a household of six, but the house is new and highly insulated and there were times when we did have to ration use, either by turning the heating off before evening baths & showers (not normally a problem), or by staggering said ablutions across the evening. Not terribly difficult with young children, but not terribly easy with teenagers.

Oh, and the cost. Electricity is currently 4× the price of gas per kWh and has been higher (and lower). Crudely, the price of our gas boiler will be paid back within 18 months or so purely on energy bill savings (very crudely - there are other considerations which mean it's actually a little longer).

Which brings me back to heat pumps too. In general an air-source heat pump is only 2:1 efficient across the year, from several long-term studies I have read. Yes, in the summer they can manage 4:1, maybe more, but in the winter they are little better than resistive heaters (and under some conditions they are worse), mainly due to having to reach high temperatures for the hot water to the taps (they get less efficient as they work harder) so however you look at it, they will cost twice as much to run as a gas boiler (four times the fuel cost but uses half the amount of fuel).

And at the risk of being deleted again for going off topic, insulate, insulate, insulate

Edit: this post was moved from a separate discussion, apologies if it appears out of place.

 

[reddragon]

I'm going to have to do some more digging, because I read a fairly recent and apparently quite well-conducted report which didn't tally with that at all (for an air-to-water system). What you say doesn't seem to make any sense unless you don't use hot water in the winter, or, in the winter the efficiency for the heating part of the system is something like 6:1 or 7:1 and I haven't even seen manufacturer claims of that figure

In addition, if your cold mains is anything like ours it will be coming into the building at about 10C (possibly higher) in the summer and 5C in the winter which will also make a difference to the efficiency, so the 2.5:1 in the summer will be lower in the winter - more heat rise required from a colder outside temperature. I do understand that water used for heating is usually much lower temperature, though that can bring its own problems (in older houses) unless you can also make some big upgrades to insulation etc.

I think my main problem is that many news reports seem to see air source heat pumps as the holy grail of environmental upgrades, and ignore all the other things that go alongside them, and "4:1" doesn't seem to be an accurate across-the-year figure.

There is a lot of 'expert' opinion out there on heat pumps that is wrong.

Heat pumps are the most efficient when heating water up a bit, say from 15C outside to 35C hot water for underfloor heating, efficiencies of 7:1

They are the least efficient at big temperature differences say from 15C to 65C for hot water or badly insulated houses on old rad systems, often below 2:1.

In the winter most energy used is to heat from 5-10C to 35C for underfloor heating (or large rads), so around 4:1 to 5:1, a small % goes to heat water from 10C coming in to 65C giving an overall efficiency of 4:1
In the summer all the energy is to heat water from 15C to 65C at 2:1 but proportionately the energy use is so small the annual averages about 4:1. Reduce that hot water temperature & you still get 4:1.

-------------------------

I do not have a heat pump (other than the fridge) but: -

In the winter I use Thermal heating, biomass to heat water to 65C before showers are needed and to warm bedrooms on rads. The rest of the day heat is drawn off the thermal store to heat floors in living areas at 35C

In better weather, solar thermal or diverted PV heats the tank to provide warm water, 40C+ covers showers & heating. Efficiency is at the maximum.

Initially I ran the system conventionally to 65C and got 60 days of solar heating, now I run it at low temperatures & get 150+ days of free solar heating. I use a reverse tank to avoid Legionella as all stored water is treated.

-----------

Key answer is how you operate the heat pump system can affect running costs by a factor of 2 or more, from twice the cost of gas to just a bit cheaper than gas or how I have it set up, half the price of gas.

We need industry training, experts & education to roll this stuff out.

 

[StKeverne1497]

There is a lot of 'expert' opinion out there on heat pumps that is wrong.

Heat pumps are the most efficient when heating water up a bit, say from 15C outside to 35C hot water for underfloor heating, efficiencies of 7:1

They are the least efficient at big temperature differences say from 15C to 65C for hot water or badly insulated houses on old rad systems, often below 2:1.

Well, I'm going to have to do some more research then because I've just looked at this brochure by Viessmann and am somewhat confused by the terminology. In one part of the table it claims a COP of around 5:1 for heating with air at 7C and water at 35C, which seems very good, but in another part of the table it gives an Energy Efficiency ηs figure for water@35C of between 178% and 190%, that is well below 2:1. For water@55C this drops to between 141% and 145%

According to this piece of legislation, ηs refers to the seasonal efficiency of space heating including certain "corrections" and is "the ratio between the space heating demand for a designated heating season, supplied by a heater and the annual energy consumption required to meet this demand, expressed in %". So it sounds as if Viessmann is suggesting that across a year, with a low-temperature heating system you will get out in heat energy no more than 190% of the electrical energy you put in (reading something else, it's possible that ηs might include grid efficiencies, so I suppose that might make up a small part of the difference).

A report was produced in 2017 based on data collected between late 2013 and early 2015 from heat pumps (both air- and ground-source) installed with the Renewable Heat Premium Payment scheme, quite a lot of heat pumps in other words. The main conclusion was that there was a vast variation in performance (from Seasonal Performance Factors as low as 0 (zero) to 5.5 - page 13) and that a large part of this variation was due to differences in operating conditions. In other words, this study looked at "real world" performance, not the performance obtained by systems operated by engineers. The median figure for SPF with outliers "cropped" (also p13) was 2.44 for air source heat pumps to the delivered heat outputs. (note the "Hn" boundaries - explained in appendix A1 on p40).

This level of efficiency was enough to provide CO2 savings against all other fuels, even with the generation mix used (2015 I think, can't find the reference now - whatever, it will only have improved in the years since as more renewable generation comes online), but it was not enough to provide cost reductions against gas or oil at 2016 prices; in fact an ASHP was more expensive to run than an 85% efficient gas boiler. Prices have moved a lot since then and I can't speak for oil (or coal or LPG) but the figures from 2016 they used were 4.18p/kWh for gas and 13.86p/kWh for electricity, which is a ratio of about 3.3:1. I am currently paying about 7.43p for gas and 29.72p for electricity which is exactly 4:1 so the difference would actually be greater now than back then.

But I digress. If anyone could clear up my confusion? I realise there are a couple of different measures involved, but...

• 5:1 sounds like one of those "marketing figures" that is never achieved in practice
• however "190%" seems very low for a modern ASHP - indeed one of Viessmann's current range
• especially when compared with a measured value of 2.44:1 from heat pumps which were installed between 2009 and 2013; I can only assume efficiencies have improved since then
• and none of those figures comes anywhere near the maximum 7:1 you quote, or the overall 4:1

Edit: removed final comment; re-reading, it was irrelevant

 

[reddragon]

I have been looking into this heat pump business for 10 years, understand the high level figures & principals but cannot get to the bottom of real figures and how to calculate them or to get the best efficiency.

I have learnt: -

Rule 1 - get the design set up right
Rule 2 - insulate insulate insulate
Rule 3 - low temperature heating, maybe with night tariff immersion heater for showers etc
Rule 4 - get solar thermal / PV with diverter for summer.

I estimate that I can get a 4:1 efficiency but need to learn how!

Air - water systems are now much more efficient than in the past, ground source are much better but that gap is closing

 

[najaB]

In the winter, this meant putting them up very high in order for the flat to be warm in the evening. The downside was that it was like being in the Sahara in the mornings, so I had to open windows to let out the heat in the morning, which is an absolute waste of money.

Sounds to me like the insulation was shot. I have (briefly) used modern storage heaters and they were barely warm to the touch if the output vent was closed.

 

[bavvo]

I had stroage heaters in my flat. The flat was ground floor, well insulated but also suffered from a lot of damp from the kitchen. Anyway, I found one heater was sufficient to heat the main livingroom/kitchen area to a comfortable temperature even in the coldest day, so it wasn't too much of an issue or expensive.
I then moved to a poorly insulated 2 up 2 down victorian terrace with a storage heater in each room. The bedroom ones were unusable because they would roast you overnight, and the downstairs ones were unable to get the rooms warm enough. I replaced them all with regular radiators and a combi boiler and also insulated under the floor and replaced the windows. Now the place is toasty in winter and my bills (last year) were halved. I think storage heaters can work in some circumstances, but I'd prefer another solution.

 

[Magdalia]

I bought a new flat about 40 years ago. There was no gas, so electric was the only option. It was a small flat, and I wasn't there much of the time, either being working or on the trains, so at first I managed with an electric 2kW convector heater. I succumbed to night storage heaters in the winter of 1986/87, which was bitterly cold, with temperatures rarely getting above freezing even during the day.

Anything is superior to a heating system where you have to decide if you want the heating on or not the day before. Awful things. Have you ever lived in a place that had them?

This is the first big problem. I learned to be a weather forecast obsessive, something that I've still not shaken off.

The second big problem is that the time you most want the heat is in the evening, which is a long time after the Economy 7 slot. Sometimes I'd get home to find no heat left "in store".

In those days the economics of Economy 7 were supply side driven, inextricably linked with finding a use for nuclear power generated at night. Is that still relevant now?

 

[Bletchleyite]

It is probably relevant now, but soon it will be taken to charge EVs instead. Electricity in the middle of the day may end up cheaper.

 

[najaB]

In those days the economics of Economy 7 were supply side driven, inextricably linked with finding a use for nuclear power generated at night. Is that still relevant now?

Not just nuclear - pretty much all thermal plants operate more efficiently at a constant load, so it was just as much about keeping the turbines spinning at coal-fired plants as it was nuclear.