5 ms·

Is that "no gain" in terms of energy (i.e. heat energy out = electricity in), or financial (i.e. cost of electricity consumed by heat pump = cost of equivalent

Is that "no gain" in terms of energy (i.e. heat energy out = electricity in), or financial (i.e. cost of electricity consumed by heat pump = cost of equivalent gas-fired system)? EDIT: or is it "well-to-wheels" style energy (i.e. primary energy consumed by heat pump = primary energy consumed by gas boiler), or is it CO2 (same emissions)

iso1631 4y ago
With a 1:1 ratio it's heat energy out = electricity in, minus a small amount of efficiency loss (any heat produced on an external heater) As to cost wise it depends on the cost per kWh of your electricity vs gas. In the UK gas is far cheaper per kWh. CO2 wise it depends on the CO2 intensity of your electric source vs a local gas burner. However that only applies when it's -20C. When it's a more reasonable like now at 7AM in Chicago when it's 2 degrees C, you're generating something like 2.5kWh of heat for every 1kWh of electricity. That may not be financially beneficial if your gas is 5c/kWh and electricity is 30c/kWh, that depends on your various deals. For me in the UK, my external oil boiler this winter has cost about 10p/kWh. My electricity is 21p/kWh. A heat pump I looked at was a 3.84 ratio, so if that ratio held down as far as typical winter temperatures of 6C (it's currently 11C), that would be 5.5p/kWh, and obviously far less CO2 per unit of heat.
- Jochim 4y ago
  Last time I checked, replacing an existing gas installation with a heat pump in the UK just wasn't economically sensible. Air source heat pumps were barely breaking even compared to gas so you'd be spending £10k+ to install it without saving any money. Ground source heat pumps offered better efficiency but if I recall correctly purchase + installation was a £35k investment that would take decades to recoup. There's also the consideration of additional costs due to lower running temperature which often necessitate larger radiators. They might make more financial sense if energy costs stay high, since they're easier to supplement with domestic renewables.
  - monkeynotes 4y ago
    Is that £10k for a mini split system? I'm not sure how many homes would need to spend that much. The UK is full of small flats and 2 up/down places that could rely on maybe one or two splits, Google shows that a decent setup would be about £2k plus installation (two splits each at £1k inc tax). Given the hot summers and energy costs in the UK I think many homes would find that investment a net gain. > There's also the consideration of additional costs due to lower running temperature which often necessitate larger radiators. I don't know what that means. There are no radiators for mini splits or air source heat pumps, maybe you are talking about ground source hot-water systems? They are still stupidly expensive, for good reason, huge install consideration. Today's low upfront cost of mini split heat pumps makes for a highly favourable option for new builds, and indeed even the average home.
    - Jochim 4y ago
      > Is that £10k for a mini split system? It was 2021 when I last last looked into it but I recall that 10k was the list price of the cheapest air source heat pump that wouldn't result in a net increase in energy bills. I don't believe it included installation or any other associated costs. > Given the hot summers and energy costs in the UK I think many homes would find that investment a net gain. It's almost unheard of for UK homes to have any sort of cooling installed. > I don't know what that means. There are no radiators for mini splits or air source heat pumps, maybe you are talking about ground source hot-water systems? They are still stupidly expensive, for good reason, huge install consideration. UK homes are mainly heated with hot water radiators in each room; typically by an on demand gas combi-boiler that also handles hot water. Heat pump installations in the UK typically heat a hot water tank[0] that provides domestic hot water and heats the radiators. Due to poor insulation the gas central heating systems typically run at around 60-80c. Heat pumps here usually heat the water to around 40c. This will often require replacing existing radiators that were installed expecting ~70c flow temperature with oner that can disperse more heat into the room. It can also involve additional insulation. > Today's low upfront cost of mini split heat pumps makes for a highly favourable option for new builds, and indeed even the average home. Indeed, heat pumps are a sensible choice for most new build homes in the UK as well. They typically have much better insulation and are therefore less affected by the low flow temperature. The costs involved in retrofitting anything older than 10, maybe 20 years old were. [0] https://solarthermuk.co.uk/wp-content/uploads/2020/12/air_source_heat_pump.jpg https://solarthermuk.co.uk/wp-content/uploads/2020/12/air_so...
Tor3 4y ago
The only heating around here these days is electrical (edit: except for wood stoves, which are usually allowed). Oil isn't allowed, and gas heating doesn't exist. So yes, "no gain" means that the heat output is equivalent to the electricity input (at the low turning point, which is around -20C for my pump - I should qualify that though, it used to be when it was new, but the tech who checked my pump a couple of years ago said it had lost some of its efficiency due to various things including some difficult to remove grime inside, but there still was no point in actually replacing it). Of course, there's also the installation costs of a heat pump. But it did pay for itself in a reasonably short time. If it hadn't been that efficient it wouldn't have - first, there's the actual price, which is not as much these days as it used to be, but then there's the actual installation by a pro, and I believe that part has only gone up since then.
- bitexploder 4y ago
  Small installations are pretty simple if you can run the electric yourself. Then just hire an HVAC tech to purge the lines and fill to manufacturer specs. Done. Complex installs with multiple head units per outdoor unit get complicated as you have maximum and minimum line lengths and the length of installed line impacts amount of refrigerant needed and such, takes a good bit of planning and knowledge.
jghn 4y ago
This is a good point. And I'd imagine most people when talking anecdotally on their own experience are comparing based on cost. And of course costs will vary. For instance we have a heat pump that we mostly use for AC. Our primary heat is a gas boiler feeding steam radiators. We'll use the heat pump in the shoulder seasons when you just want to take the chill out of a specific room, but usually nothing else heat wise. Last winter our boiler died and we spent about a month without it. That provided me a good opportunity to do something closer to apples/apples. Despite having the cold weather rated heat pump (Mitsubishi HyperHeat2) the extra electricity consumed that month was about the same as our typical gas cost. A slight bit more actually. But I have no idea about energy usage in an objective sense. And if I really wanted to go down this rabbit hole, we're subscribed to an energy plan that's mostly based on renewables whereas obviously 0% of our gas is the same.
- space_fountain 4y ago
  I think almost matching gas energy costs implies dramatically lower total energy used and the benefits of being able to use renewables. Natural gas can only really win in terms of heating because producing heat is easier than producing electricity with the same gas
  - jghn 4y ago
    Quite possible. In our case it is academic as due to quirks of our house configuration (the joys of a house pushing 200 years old) we can only get units in a couple of rooms. It's good enough to keep the house cool in the summer, and heat the house in a real emergency like last winter but not something we can rely on for primary heat.

iso1631 4y ago

With a 1:1 ratio it's heat energy out = electricity in, minus a small amount of efficiency loss (any heat produced on an external heater) As to cost wise it depends on the cost per kWh of your electricity vs gas. In the UK gas is far cheaper per kWh. CO2 wise it depends on the CO2 intensity of your electric source vs a local gas burner. However that only applies when it's -20C. When it's a more reasonable like now at 7AM in Chicago when it's 2 degrees C, you're generating something like 2.5kWh of heat for every 1kWh of electricity. That may not be financially beneficial if your gas is 5c/kWh and electricity is 30c/kWh, that depends on your various deals. For me in the UK, my external oil boiler this winter has cost about 10p/kWh. My electricity is 21p/kWh. A heat pump I looked at was a 3.84 ratio, so if that ratio held down as far as typical winter temperatures of 6C (it's currently 11C), that would be 5.5p/kWh, and obviously far less CO2 per unit of heat.

Jochim 4y ago
Last time I checked, replacing an existing gas installation with a heat pump in the UK just wasn't economically sensible. Air source heat pumps were barely breaking even compared to gas so you'd be spending £10k+ to install it without saving any money. Ground source heat pumps offered better efficiency but if I recall correctly purchase + installation was a £35k investment that would take decades to recoup. There's also the consideration of additional costs due to lower running temperature which often necessitate larger radiators. They might make more financial sense if energy costs stay high, since they're easier to supplement with domestic renewables.
- monkeynotes 4y ago
  Is that £10k for a mini split system? I'm not sure how many homes would need to spend that much. The UK is full of small flats and 2 up/down places that could rely on maybe one or two splits, Google shows that a decent setup would be about £2k plus installation (two splits each at £1k inc tax). Given the hot summers and energy costs in the UK I think many homes would find that investment a net gain. > There's also the consideration of additional costs due to lower running temperature which often necessitate larger radiators. I don't know what that means. There are no radiators for mini splits or air source heat pumps, maybe you are talking about ground source hot-water systems? They are still stupidly expensive, for good reason, huge install consideration. Today's low upfront cost of mini split heat pumps makes for a highly favourable option for new builds, and indeed even the average home.
  - Jochim 4y ago
    > Is that £10k for a mini split system? It was 2021 when I last last looked into it but I recall that 10k was the list price of the cheapest air source heat pump that wouldn't result in a net increase in energy bills. I don't believe it included installation or any other associated costs. > Given the hot summers and energy costs in the UK I think many homes would find that investment a net gain. It's almost unheard of for UK homes to have any sort of cooling installed. > I don't know what that means. There are no radiators for mini splits or air source heat pumps, maybe you are talking about ground source hot-water systems? They are still stupidly expensive, for good reason, huge install consideration. UK homes are mainly heated with hot water radiators in each room; typically by an on demand gas combi-boiler that also handles hot water. Heat pump installations in the UK typically heat a hot water tank[0] that provides domestic hot water and heats the radiators. Due to poor insulation the gas central heating systems typically run at around 60-80c. Heat pumps here usually heat the water to around 40c. This will often require replacing existing radiators that were installed expecting ~70c flow temperature with oner that can disperse more heat into the room. It can also involve additional insulation. > Today's low upfront cost of mini split heat pumps makes for a highly favourable option for new builds, and indeed even the average home. Indeed, heat pumps are a sensible choice for most new build homes in the UK as well. They typically have much better insulation and are therefore less affected by the low flow temperature. The costs involved in retrofitting anything older than 10, maybe 20 years old were. [0] https://solarthermuk.co.uk/wp-content/uploads/2020/12/air_source_heat_pump.jpg https://solarthermuk.co.uk/wp-content/uploads/2020/12/air_so...

Tor3 4y ago

The only heating around here these days is electrical (edit: except for wood stoves, which are usually allowed). Oil isn't allowed, and gas heating doesn't exist. So yes, "no gain" means that the heat output is equivalent to the electricity input (at the low turning point, which is around -20C for my pump - I should qualify that though, it used to be when it was new, but the tech who checked my pump a couple of years ago said it had lost some of its efficiency due to various things including some difficult to remove grime inside, but there still was no point in actually replacing it). Of course, there's also the installation costs of a heat pump. But it did pay for itself in a reasonably short time. If it hadn't been that efficient it wouldn't have - first, there's the actual price, which is not as much these days as it used to be, but then there's the actual installation by a pro, and I believe that part has only gone up since then.

bitexploder 4y ago
Small installations are pretty simple if you can run the electric yourself. Then just hire an HVAC tech to purge the lines and fill to manufacturer specs. Done. Complex installs with multiple head units per outdoor unit get complicated as you have maximum and minimum line lengths and the length of installed line impacts amount of refrigerant needed and such, takes a good bit of planning and knowledge.

jghn 4y ago

This is a good point. And I'd imagine most people when talking anecdotally on their own experience are comparing based on cost. And of course costs will vary. For instance we have a heat pump that we mostly use for AC. Our primary heat is a gas boiler feeding steam radiators. We'll use the heat pump in the shoulder seasons when you just want to take the chill out of a specific room, but usually nothing else heat wise. Last winter our boiler died and we spent about a month without it. That provided me a good opportunity to do something closer to apples/apples. Despite having the cold weather rated heat pump (Mitsubishi HyperHeat2) the extra electricity consumed that month was about the same as our typical gas cost. A slight bit more actually. But I have no idea about energy usage in an objective sense. And if I really wanted to go down this rabbit hole, we're subscribed to an energy plan that's mostly based on renewables whereas obviously 0% of our gas is the same.

space_fountain 4y ago
I think almost matching gas energy costs implies dramatically lower total energy used and the benefits of being able to use renewables. Natural gas can only really win in terms of heating because producing heat is easier than producing electricity with the same gas
- jghn 4y ago
  Quite possible. In our case it is academic as due to quirks of our house configuration (the joys of a house pushing 200 years old) we can only get units in a couple of rooms. It's good enough to keep the house cool in the summer, and heat the house in a real emergency like last winter but not something we can rely on for primary heat.