Phasing out oil boilers - can anyone give me the definitive situation!

QrizB

Ectophile said:

The reason that you need insulation is that heat pumps work most efficiently at lower output temperatures.  So that means pumping warm, not hot, water around the system..

With respect, you're agreeing with me. When you say "heat pumps work more efficiently at lower output temperatures" you're making an economic argument, not a capability one.

Ectophile said:

So unless you line all the walls with radiators, a heat pump system will never adequately heat a badly insulated house.

A heat pump with a 60C flow temperature will heat a property just as effectively as a condensing boiler with a 60C flow temperature will.

Reed_Richards

QrizB said:

Domestic heat pumps seem to go up to about 18 kW of heat output. 

And there was a thread recently over on the main Energy forum about a 5000 sq. m. house with three-phase power and two separate heat pumps, so I suspect you could install 3x 18kW heat pumps if you really needed 54kW of heat input to your home.

All the claims that "heat pumps need well insulated homes" are shorthand for "heat from heat pumps is often more expensive than oil or gas, so insulation is likely to be more cost-effective".

If you need multiple heaters to heat your home, that's liable to be more expensive than using one large one.  So whilst using multiple heat pumps is certainly feasible, it might well be a lot more costly than using a single large oil boiler, if you can manage to do that.

When I bought my heat pump at the end of 2020 then heat from a heat pump was pretty cost competitive with heat from oil but more expensive than heat from gas.  At present, heat from a heat pump is cost competitive with heat from gas but heat from oil is cheaper than either.

Back when I bought my heat pump you could get a government grant towards the cost, but only if your house was well-enough insulated.  I wonder if that was the source of the claim that "heat pumps need well insulated homes"?    

FreeBear

Ectophile said:  a heat pump system will never adequately heat a badly insulated house.

The same can be said for any other form of heating. A poorly insulated and draughty house is always going to be difficult (and expensive) to heat. And if the heating is badly configured, that just compounds the problem.

My mother used to complain about being cold and the heating system never seemed to keep the house warm. In recent years, I've replaced doors & windows, insulated in places, plugged the cold draughts, and put in a couple of larger radiators. Staying warm without spending a fortune is now a lot easier.

Over the last couple of months, I've replaced the central heating system, and will find out if it has been worthwhile come the winter - The work was done with an eye on the future when heat pumps are the only option.

Fredw56

There are lots of partisan and often misleading statements re ban on oil boilers. We have one so are following it carefully. 

Whenever the government start messing in the market there is a rash of exploitation. Grants are less for the customer and more for inflating the profits of the suppliers. The idea is a motivate a bunch of carpetbaggers to set up and flog loads of stuff by blagging folk about grants. Once the gold rush is over the carpetbaggers disappear in a puff of limited liability. 

Stick with oil pending end of the gold rush and normalisation of a diffused market in heat pumps. But. It’s a big but. Wait until they are domestic sized heat pumps with CO2 refrigerant. They can produce higher temperatures and hence can deliver sufficient energy through most existing central heating pipes. Make sure they are modulating heat pumps so you don’t have to get scammed into a buffer tank. Should yield good savings, a direct replacement even if the CO2 heat pump costs more and uses a bit more electricity (higher compression rates). 

Most U.K. homes have bad fabric energy efficiency and it is difficult to make them as good as we would like. I have tried and not done too bad. I have also designed and built SAP A rated new houses. The latter is easy if you do it right from the design. On the “we are where we are” basis, we can’t fix all the old houses unless we have a lot of spare houses. Breaking out and insulating a ground bearing slab floor is not occupant friendly. Where would all the people go while we make life unbearable while ripping out floors? We can’t and people won’t so the country will have to do the best it can and we will but stuck with higher than ideal energy use until the older buildings are replaced. That said, none of that is worth much if we still make electricity from fossil fuels. F gas heat pumps running at sub 40 degrees burning dirty electricity in an old British house are not a great solution.

if someone markets a truly modulating oil boiler and genuine vegetable oil fuels are approved (with no Palm Oil) there may be longer life for oil (vegetable). That’s a holy grail which may never happen. A total ban on import of all palm oil for any use would be a good start. Stuff the food industry, their processing has been giving us all dementia and cancer for generations so I don’t care about them.

Ectophile

QrizB said:

Ectophile said:

The reason that you need insulation is that heat pumps work most efficiently at lower output temperatures.  So that means pumping warm, not hot, water around the system..

With respect, you're agreeing with me. When you say "heat pumps work more efficiently at lower output temperatures" you're making an economic argument, not a capability one.

Ectophile said:

So unless you line all the walls with radiators, a heat pump system will never adequately heat a badly insulated house.

A heat pump with a 60C flow temperature will heat a property just as effectively as a condensing boiler with a 60C flow temperature will.

It will, but you won't be able to afford to run it at that temperature.

Reed_Richards

Ectophile said:

QrizB said:

Ectophile said:

The reason that you need insulation is that heat pumps work most efficiently at lower output temperatures.  So that means pumping warm, not hot, water around the system..

With respect, you're agreeing with me. When you say "heat pumps work more efficiently at lower output temperatures" you're making an economic argument, not a capability one.

Ectophile said:

So unless you line all the walls with radiators, a heat pump system will never adequately heat a badly insulated house.

A heat pump with a 60C flow temperature will heat a property just as effectively as a condensing boiler with a 60C flow temperature will.

It will, but you won't be able to afford to run it at that temperature.

You might afford it if you are wealthy enough but it would be considerably cheaper to run at 50 C flow temperature, and a lot cheaper still at 40 C flow temperature.  Those people waiting for a souped-up high temperature heat pump are missing the point.  The laws of physics dictate that however high a temperature the heat pump can operate at, it will always be cheaper to run it at lower temperatures.  For that you need radiators with a larger surface area (or underfloor heating) but they'll quickly pay for themselves in reduced heating bills.   

lohr500

Is it still not the case though that at current pricing for oil and electricity, an oil boiler will be cheaper to run than an ASHP? Irrespective of flow temperatures, the need for bigger radiators, better insulation or any other factors that are being discussed.

In our area oil is currently £0.70 per litre and the electric SVT is £0.29 per unit. Both including VAT.

1 litre of oil yields 10.35kWh at 100% efficiency. Call it around 9.3kWh at 90% boiler efficiency. Or £0.075 per kWh, based on oil at £0.70 per litre.

If I understand it correctly a well setup ASHP should achieve about a 3:1 efficiency gain. £0.29/3 = £0.097 per kWh 
The ASHP would need to achieve an efficiency of about 3.8:1 to match the oil cost per kWh.

Green consideration aside, why would anyone want to take on board the significantly higher cost of replacing an oil boiler with an ASHP based on today's energy costs?

If the £5k grant covered the real oncost for making the switch, including the higher cost of the ASHP unit/installation and changes to all the radiators/plumbing, then I guess the running cost variance is arguably marginal and subject to the ebb and flow of the respective electricity and oil market forces.

But in our case for sure, £5k wouldn't have covered the switching costs to twin 18kW ASHP units, a move to a 3 phase electricity supply and changes to 15 radiators. Even the £12k we could have got a couple of years ago didn't make the numbers add up.

orbit500

Reed_Richards said:

Ectophile said:

QrizB said:

Ectophile said:

The reason that you need insulation is that heat pumps work most efficiently at lower output temperatures.  So that means pumping warm, not hot, water around the system..

With respect, you're agreeing with me. When you say "heat pumps work more efficiently at lower output temperatures" you're making an economic argument, not a capability one.

Ectophile said:

So unless you line all the walls with radiators, a heat pump system will never adequately heat a badly insulated house.

A heat pump with a 60C flow temperature will heat a property just as effectively as a condensing boiler with a 60C flow temperature will.

It will, but you won't be able to afford to run it at that temperature.

You might afford it if you are wealthy enough but it would be considerably cheaper to run at 50 C flow temperature, and a lot cheaper still at 40 C flow temperature.  Those people waiting for a souped-up high temperature heat pump are missing the point.  The laws of physics dictate that however high a temperature the heat pump can operate at, it will always be cheaper to run it at lower temperatures.  For that you need radiators with a larger surface area (or underfloor heating) but they'll quickly pay for themselves in reduced heating bills.   

Exactly. A heat pump pulling 60c water from 0c air can never exceed COP 5.5 even using angel’s tears as refrigerant.

Fredw56

Reed_Richards said:

Ectophile said:

QrizB said:

Ectophile said:

The reason that you need insulation is that heat pumps work most efficiently at lower output temperatures.  So that means pumping warm, not hot, water around the system..

With respect, you're agreeing with me. When you say "heat pumps work more efficiently at lower output temperatures" you're making an economic argument, not a capability one.

Ectophile said:

So unless you line all the walls with radiators, a heat pump system will never adequately heat a badly insulated house.

A heat pump with a 60C flow temperature will heat a property just as effectively as a condensing boiler with a 60C flow temperature will.

It will, but you won't be able to afford to run it at that temperature.

You might afford it if you are wealthy enough but it would be considerably cheaper to run at 50 C flow temperature, and a lot cheaper still at 40 C flow temperature.  Those people waiting for a souped-up high temperature heat pump are missing the point.  The laws of physics dictate that however high a temperature the heat pump can operate at, it will always be cheaper to run it at lower temperatures.  For that you need radiators with a larger surface area (or underfloor heating) but they'll quickly pay for themselves in reduced heating bills.   

Low temperature water carries less energy, remember 4.18J/g/K. You need that higher temperature for the houses you can’t bring up to high fabric energy efficiency, that’s most of the existing stock. To get it into the radiators or any emitter you have to increase the capacity of the pipes. Traditional systems with 22, 15 and 10mm do not work as frequently pointed out by low temp heat pump suppliers (the ethical ones). That is more cost, mess and disruption and unsightly installations which people will not tolerate. You have to bring the population with you rather just taking the view from your ivory tower. CO2 refrigerant is not science fiction, it exists, it works. CO2 refrigerant systems just need to be brought to domestic scale and production raised to meet challenge the economies of scale. Right now the heat pump suppliers are making inflated profits from riding on adapted aircon tech originally aimed at warmer climates. It’s cheap and easy but fails to meet our the requirements of our antiquated building stock and is environmentally dangerous. Yes dangerous, hence gradual F gas restrictions to reduce global warming potential. Imagine millions of badly maintained heat pumps full of gas with hideously high GWP leaking all over the country. CO2 is, perhaps perversely, quite benign. Without F gas we can get rid of the outrageous greed of F gas contractors too. 

CO2 refrigerant will eliminate upgrading pipe diameters, if modulating (and they will be) eliminate absurdly expensive buffer tanks and heat the less than good houses. The solution would be a more expensive heat pump but minimal disruption and lesser overall cost so more chance of uptake. People won’t have to consider moving out or putting a lot of stuff into storage. Sick, disabled and elderly people won’t have to be sent, well where exactly? 

in short. A workable solution in our poor housing stock with less costs and less disruption will find a more receptive public. Just needs an effective higher temperature heat pump, like CO2 refrigerant types . I look forward to heat pumps being like washing machines, wheel it in to the garden or whatever, hook it up, job done. 

QrizB

Fredw56 said:

Low temperature water carries less energy, remember 4.18J/g/K. You need that higher temperature for the houses you can’t bring up to high fabric energy efficiency, that’s most of the existing stock. To get it into the radiators or any emitter you have to increase the capacity of the pipes. Traditional systems with 22, 15 and 10mm do not work as frequently pointed out by low temp heat pump suppliers (the ethical ones).

I'm not sure where you are getting your info but your understanding of thermodynamics is imperfect and I have neither the time nor inclination to point out all your errors.

Instead, here's an anecdote. Last winter (not an especially cold one) my patchily-insulated 1950s semi was kept pleasantly warm by a gas boiler running a ~50C flow temperature.