Oxford study proves heat pumps triumph over fossil fuels in the cold

a journalist saying that a COP above 1 means the heat pump “creates energy”

But what’s great is that this COP of 2, while bad, is not catastrophic. That’s still in territory where gas boilers are more cost efficient that a heat pump, but unless you are living in a place that is consistently under -10C for several months, then a heat pump has overall lower running costs than a gas boiler. And you are starting to hit pretty northern territories with this.

I actually have a hybrid furnace/heat pump system, and I live in southern Ontario, Canada. The furnace is the auxiliary heat source and it only kicks in when the outdoor temp is below -6C. I've only had this system through one winter so far, but I think I could count the number of days the furnace ran without running out of fingers. My electricity bill went up some of course, but my winter gas bill went down a lot.

Edit to add: I wasn't shopping for a hybrid system in particular, but I got this upgrade through the Canada Greener Homes Grant and there were limitations on which units qualified for rebates. For my install (forced-air with existing duct-work), the hybrid systems were the ones that qualified.

Even the study could have used some better clarification on geothermal HVACs, which is the direction we should all be heading towards:

Ground-source heat pumps typically provide a very high level of efficiency, even during cold weather. The reason is that soil temperature does not change significantly between seasons, resulting in a higher—and more constan—COP. In addition, ground-source heat pumps do not need to expend energy on defrosting.

This commentary focuses on the performance of air-source heat pumps in mild European winters with average January temperatures above −10°C. We refer to these heating conditions as “mild cold climates”, whereas those with average temperatures below −10°C in the coldest month are designated “extreme cold climates”.

No, why?! Gimme the COP on geothermal. Google tells me it's 3 to 5, but I would have liked a better source.

Regardless, while I understand that we should spread out our solutions, I don't understand why we're not talking more about geothermal HVAC systems. Household solar is all the rage, but my gas company is still charging me $25 a month just to have the gas on, never mind the winter costs.

If we're talking about $5K a hole to dig for geothermal, that seems like a hell of a lot more cost-effective solution than either gas-based HVACs, or these air-based heat pumps. If it's an area with only mild winters, you probably only need the one hole, which will last for 100 years at least. At most, we're talking about 3-4 holes for a large house in Canada, and that's going to pay for itself in 10-15 years.

That’s still in territory where gas boilers are more cost efficient that a heat pump.. a heat pump has overall lower running costs than a gas boiler

You just contradicted yourself.. what did you mean here?

Electricity is 3x the cost of gas, so unless the heat pump has the COP of 3 or above it is more expensive to run. Once you factor in the high cost of installation people aren't installing these things to save money.

brb putting in my window unit from the outside

Under the conditions you describe, a hybrid setup will work best.

In a hybrid setup, the heat pump is providing most heat when it isn't very cold, while the traditional heat source is providing heat on really cold days.

A few years ago, the temperature where the system would switch was 5 C. Nowadays it's more like -10 C. As heat pumps get better, hybrid loses territory, so you could also just wait a few years and then switch.

Hybrid gives best of both worlds at the cost of added complexity.

If you have A/C then the cheap way to do hybrid is to keep the traditional heating system but use the A/C in heating mode on mild days.

If you are comparing gas to heat pump efficiency, it is more like 85-90% vs 350-500% efficiency.

Because in the gas furnace efficiency they only calculate the efficiency of burning gas but miss to include the auxiliary electricity that is needed to run the system.

In a heat pump system everything (running fans etc.) is included in the efficiency calculation. The efficiency itself is depending on the source of the heat pump. In a really harsh climate a ground / geo thermal source might make sense. But usually the average temperature is higher than you might think.

And for the environmental effect: modern gas power plants run at 50-60% efficiency so with a heat pump you are always burning less gas even if the gas plant is less efficient then the gas furnace.

It would be interesting to know what extreme cold means.

For sure look into any subsidies available to you and see if they make a dual fuel system feasible. In your situation if you buy a high efficiency furnace, it may never make economic sense to run the heat pump, but things could always change and it's a simple enough task to find your break even (economic balance) point when fuel prices change. My current break even point is well beyond the temperature you would consider running heat, but I still run my heat pump in the shoulder seasons to exercise it.

Your mini-split isn't designed to function as a heat pump at low temperature.

In places like Sweden, they also use heatpumps that are designed for those conditions.

In other news, don't drive in a Swedish winter with summer tires.

My air heat pump has been ticking away happy for 15 years with no issues. It's worked fine warming up the house when it's -20°C in the winter and cooled nicely in the up to +30°C in the summer.

I do supplement it using electric heating and a fireplace though.

You used two temp scales in the same sentence

Yes, there are cold weather heat pumps that can thaw the coils to keep operating. There is a point where they just can't continue to operate.

When I design a heat pump system in cold climates, I always include a secondary hear source that kicks in if the heat pump gets overwhelmed. Might be a gas section in a furnace. Might be an electric heater in a fan coil. Might be electric baseboards or wall heaters.

Theres different technology but there are some that can function to -32° F and they often have a feature that allows them to detect when theyre frozen up and defrost and then automatically switch back to heating

Oh I have no idea, I just got to this thread and see you're at -6.

It's weird because I thought it was an informative post. Made me want to look more into it and if it was just a subsection of heat pumps that was affected.

Yes, most installations do require a backup heat source in the event outside temperature is too low for optimal heat pump usage. On my ecobee thermostat, you can set what this temperature threshold is (i.e. 20F) and then if the outside temperature falls below this value, the heat pump is stopped and the natural gas in my case kicks in. Granted, this doesn't happen often where I live, but for those few weeks in the winter, it is not something I even have to think about. And the rest of the time, I am saving money using the heat pump and not natural gas.

I doubt there can ever be high tech heat pumps which can operate at -25 C or less, because there's so little heat energy outside and the heat pump would probably spend a majority of the time running in reverse to dethaw the unit to prevent it freezing over.

Man they pitchfork mob came out in full force for this one. I also live in the south and during the freeze of 2021 it was a struggle for it to deal with those low temps.

Mind me asking what yours cost?

Just got a Toshiba unit installed in Norway and it was $3500.
Built in de froster.

Price might be what makes yours strugle in colder temps.

There absolutely have been new heat pumps hitting the market in the past year or two that are blowing away the previous generation.

Your mini split probably doesn't have a defrost function. This would all be specified in the users manual.

They actually added a correction at the end for that

That's -17.8 C, so pretty close to the limit mentioned here

They work in Sweden... and Canada...

Sure it does. Unless your average temp in January is under 5F? And on those really cold days the gas furnace kicks in anyway, so you get the most efficient heating no matter what.

Your information is outdated. It is even clearly mentioned in the one-sentence summary in the OP:

Oxford study proves heat pumps triumph over fossil fuels in the cold::Published Monday in the scientific journal Joule, the research found that heat pumps are two to three times more efficient than their oil and gas counterparts, specifically in temperatures ranging from 10 C to -20 C.

This is the correct take for a conventional heat pump. However, there are relatively new geothermal heat pumps that can heat down to -30°C (-22°F) and are much more efficient.

https://www.cbc.ca/news/science/heat-pump-faq-1.6824634

Thankfully heat pumps have gotten better since your father's day. And natural gas is only going to keep getting more expensive. For a price of equipment that will last you 15-25 years it's becoming harder to justify gas heating.

For new builds ground source heat pumps should become more standard, they cost more, but they'll save a lot in the long run.

But its all irrelevant because the most effective way to keep warm is to continue with global warming. Soon we wont have a cold season to worry about. 😜

If you're on propane, it's more likely to be cheaper. Particularly over the course of an entire heating season, because they're more efficient in fall and spring than the coldest part of winter.

But yeah, this study wasn't looking at cost per therm but just raw COP, which is a pointless metric. It doesn't even compare the number of watts of heat from burning natural gas in a furnace vs in a modern power plant that supplies a heat pump. Although since we don't have a carbon tax, that's only a theoretically interesting comparison.

Heat pumps work fine for most people in the north. Mitsubishi's cold climate heat pumps supply 85% of their rated heat at -13F. Buffalo is a city known for its winters, and the last time Buffalo's lowest temperature was below that was 1982. They're just going to be a more expensive option for most people right now.

Well, some people don't put money higher than the ability of humanity to survive.

So the cost is less relevant than the pollution.

My father in law went to a heat pump instead of propane this year. No natural gas where he lives.

But he also dropped 20k on a solar system to power it.

Ditto. At least with gas I'm not paying Alabama Power's rates.

If you posted that earlier today you would have gotten a spanking for saying anything critical about heat pumps. Or people just don’t like me in particular. Hard to tell.

The vast majority of gas boilers use electronics to function. In a powercut they are also dead.

Now if you're talking diesel generator back ups, then far enough.

We're also going to run out of oil in the next 40-45 years, so we should factor that in.

The 2 times (living not with my parents anymore) I had now electric power unplanned was of course when it was cold. However the fancy central heating running on gas was also not working. As the main unit also needed electric power.

So I could still cook my food but that's was it. No heat. But that being said in my entire life we lost power (including as a kid) maybe 5 times and only for a couple of hours. In 33 years

I now have a heat pump and for cooking induction. So in a power outage I need to grab some camping gear. But I will probably survive for a couple of hours without heat.

But if you have regular power outages you and everybody in your country should probably vote and make your voices heard. If you live in a country where most people can afford heat pumps, the government can afford fixing the power grid.

I have a duel fuel system (heat pump + gas furnace) which, while more expensive, is really the best of both worlds.

In a power outage I can plug in a generator and get the furnace running.

If temps drop too low and the heat pump is struggling I can switch to the furnace.

I can choose which to run based on current energy costs.

When looking into heat pumps everyone told me they don't work well in the northeast or they would be more expensive to run here. I found it really difficult to get an accurate estimate of the cost difference between running a heat pump vs a gas furnace. Ultimately I decided to go dual fuel for flexibility but after comparing my bills before and after I almost wish I'd gone with a hyper heat unit so it could run at lower outdoor temps because the heat pump has turned out to be cheaper but I can't run it at low temps.

I think HVAC techs in this area are weary of them based on past experience with older units but they really have improved in recent years.

I wonder who the fuck is downvoting these comments. LOL - "NO FOSSIL FUELS, YOU MUST DIE IN A POWER OUTAGE!"