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)
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.
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.
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.
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_so...
And yeah, cooling is not a thing in the UK, my point is folks are definitely going to be looking toward that given the summers people have been having, increase heating costs will make mini splits a double win. No brainer to me and I bet mini splits will be in limited supply this summer in Europe.
* How would the heat be moved around the house?
* Obtaining permission to modify the exterior of a multi-occupancy dwelling is extremely difficult.
* You'd still require a source of hot water, reducing the already small savings over an efficient combi-boiler.
Based on the estimated savings of the Energy Saving Trust, it'd take around 26 years to pay off a £3k install that replaces a modern combi-boiler[0] and that's without the cost of using electricity to provide heated water. As recently as March of this year Which claimed most houses would have paid an extra £80/year if running a heat pump[1].
They could be a good choice for completely new installs and people stuck on resistive electric heating if they can find a way to disperse the heat evenly. I'd bet a lot of money that the majority of properties with electric heating are rentals, good luck convincing a landlord to pay for anything.
[0] https://energysavingtrust.org.uk/advice/air-source-heat-pump...
[1] https://www.which.co.uk/reviews/ground-and-air-source-heat-p...
Moving the heat around the house requires doors to be open and thoughtful placement of the head units which have fans in them to push the air around. It is certainly not ideal but we are comfortable.
https://news.ycombinator.com/item?id=34233719
Obviously it depends on ability to scale, but UK rad heating systems are usually rated for 50 or 60C, thus this seems to fit the bill.
Home renewables help but require even more capital investment, often taking 10 or more years to pay off. It doesn't help that where I am solar has extremely limited output in the winter. Domestic wind turbines are difficult to situate and get planning approval for. My cursory impression is that they're also less economical than many solar installs.
I've got some roof repairs coming up soon and I'm hoping the economics of replacing the existing roof with some nice looking solar slate tiles work out favourably!
[0] https://www.statista.com/statistics/426988/united-kingdom-uk...
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.
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.
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.