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Does anyone know if they work in old houses? We have a stone house built in ~1800. We have upgraded with insulation in the floors, walls ceiling, but of course

Does anyone know if they work in old houses? We have a stone house built in ~1800. We have upgraded with insulation in the floors, walls ceiling, but of course it is still fairly draughty if it is windy. It's damn expensive to heat, and have considered an air source heat pump, but always thought that it wasn't really a good idea for old houses.

MonkeyMalarky 4y ago
There's no reason why it won't work, its just another (more efficient) source of heat.
- Jochim 4y ago
  It might work theoretically but that doesn't mean it should be done in many cases. Where I live electricity is nearly 3x the price of gas. While some heat pumps can achieve this in certain conditions it eliminates most of the affordable options which raises the question of how long are you willing to wait before a £10k-50k+ investment pays itself off? They typically operate at lower output temperatures than existing systems. For example, swapping out a gas boiler for a heat pump will often require replacing all the radiators with much larger ones as well. IIRC they're also less responsive. You might find yourself keeping the house at 18-20c all day rather than turning off rooms you aren't using. The effect is that you use more energy than you would have otherwise.
  - MonkeyMalarky 4y ago
    Right, it is decision that depends more on the economics of where you live and your usage than the age or construction of your house. Where I live, gas is not an option and there are subsidies to change over to electric and off of heating oil.
dazc 4y ago
I lived in such a house once and it was permanently cold, even with heating left on all day. In this instance the problem wasn't just the draughts but also the fact that it was connected to the old standard sized radiators that never got hot, they were always just above tepid, at best. The landlord will happily bore you senseless about how much money he's saved though.
Jochim 4y ago
They often operate at much lower temperatures than gas central heating. In older houses especially this will often require much larger radiators and/or UFH. From my research a couple of years ago: Replacing gas central heating with air source heat pumps was a waste of money, they're more energy efficient but the cost worked out the same due to gas being so much cheaper. If you have rooftop solar and batteries already and are overproducing electricity it might be a viable choice but without those you'd be spending a lot of money replacing radiators for no financial benefit. Ground source heatpumps offered a decent cost saving but were extremely expensive to install. You also need space available to sink them or a lot of lateral space if you want to save a fair bit on the install. Before the energy crisis my estimates for breaking even on installation costs were on the order of decades.
- jrochkind1 4y ago
  > due to gas being so much cheaper. I'm curious where you live. The OP suggested that gas and electricity prices vary a surprising amount throughout the US, and that gas is not usually cheaper than electricity, but is sometimes. They did suggest if you are in a place where gas is a lot cheaper than electricity, that might be the one thing to make heat pumps not cost effective, but that this was not typical. I personally do not know much about this. (I don't even know how to know if my own gas is "cheaper" than electricity, since they are metered/measured in different units!)
  - Jochim 4y ago
    I'm in the UK. Our gas is metered in m^3 but our energy suppliers typically bill and advertise based on the converted kWh price. My current prices for electricity and gas are 33.76p/kWh and 10.28p/kWh respectively. That's after a government price cap has been applied without it it's 49.15p/kWh and 14.00p/kWh Based on those prices a heat pump would need to have at least an efficiency of 3.28 (3.5 uncapped) just to break even. Given that the total cost of installation is in the range of £3k-40k there really needs to be a compelling reason to retrofit an existing house. Some of this is due to the vagaries of the UK energy markets. The outcome is that we often end up paying renewable providers of electricity based on the cost set by gas powered stations. At the moment that price has been grossly inflated due to profiteering, we're far less reliant on imported gas than mainland Europe. I'd like to note that the price savings and break even point have probably gotten better compared to when I last checked. If we go back to much warmer, happier times - like September 2020 - I was paying 15.999p/kWh and 2.915p/kWh for electricity and gas respectively. Prior to that it was 14.150p/kWh and 2.920p/kWh. At that point I believe an air source pump resulted in a net increase in my bill and a ground source heat pump would have taken around 30 years to pay off. I should probably recalculate when things have settled down a bit.

MonkeyMalarky 4y ago

There's no reason why it won't work, its just another (more efficient) source of heat.

Jochim 4y ago
It might work theoretically but that doesn't mean it should be done in many cases. Where I live electricity is nearly 3x the price of gas. While some heat pumps can achieve this in certain conditions it eliminates most of the affordable options which raises the question of how long are you willing to wait before a £10k-50k+ investment pays itself off? They typically operate at lower output temperatures than existing systems. For example, swapping out a gas boiler for a heat pump will often require replacing all the radiators with much larger ones as well. IIRC they're also less responsive. You might find yourself keeping the house at 18-20c all day rather than turning off rooms you aren't using. The effect is that you use more energy than you would have otherwise.
- MonkeyMalarky 4y ago
  Right, it is decision that depends more on the economics of where you live and your usage than the age or construction of your house. Where I live, gas is not an option and there are subsidies to change over to electric and off of heating oil.

dazc 4y ago

I lived in such a house once and it was permanently cold, even with heating left on all day. In this instance the problem wasn't just the draughts but also the fact that it was connected to the old standard sized radiators that never got hot, they were always just above tepid, at best. The landlord will happily bore you senseless about how much money he's saved though.

Jochim 4y ago

They often operate at much lower temperatures than gas central heating. In older houses especially this will often require much larger radiators and/or UFH. From my research a couple of years ago: Replacing gas central heating with air source heat pumps was a waste of money, they're more energy efficient but the cost worked out the same due to gas being so much cheaper. If you have rooftop solar and batteries already and are overproducing electricity it might be a viable choice but without those you'd be spending a lot of money replacing radiators for no financial benefit. Ground source heatpumps offered a decent cost saving but were extremely expensive to install. You also need space available to sink them or a lot of lateral space if you want to save a fair bit on the install. Before the energy crisis my estimates for breaking even on installation costs were on the order of decades.

jrochkind1 4y ago
> due to gas being so much cheaper. I'm curious where you live. The OP suggested that gas and electricity prices vary a surprising amount throughout the US, and that gas is not usually cheaper than electricity, but is sometimes. They did suggest if you are in a place where gas is a lot cheaper than electricity, that might be the one thing to make heat pumps not cost effective, but that this was not typical. I personally do not know much about this. (I don't even know how to know if my own gas is "cheaper" than electricity, since they are metered/measured in different units!)
- Jochim 4y ago
  I'm in the UK. Our gas is metered in m^3 but our energy suppliers typically bill and advertise based on the converted kWh price. My current prices for electricity and gas are 33.76p/kWh and 10.28p/kWh respectively. That's after a government price cap has been applied without it it's 49.15p/kWh and 14.00p/kWh Based on those prices a heat pump would need to have at least an efficiency of 3.28 (3.5 uncapped) just to break even. Given that the total cost of installation is in the range of £3k-40k there really needs to be a compelling reason to retrofit an existing house. Some of this is due to the vagaries of the UK energy markets. The outcome is that we often end up paying renewable providers of electricity based on the cost set by gas powered stations. At the moment that price has been grossly inflated due to profiteering, we're far less reliant on imported gas than mainland Europe. I'd like to note that the price savings and break even point have probably gotten better compared to when I last checked. If we go back to much warmer, happier times - like September 2020 - I was paying 15.999p/kWh and 2.915p/kWh for electricity and gas respectively. Prior to that it was 14.150p/kWh and 2.920p/kWh. At that point I believe an air source pump resulted in a net increase in my bill and a ground source heat pump would have taken around 30 years to pay off. I should probably recalculate when things have settled down a bit.