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Heat pumps twice as efficient as fossil fuel systems in cold weather, study finds
(www.theguardian.com)
this post was submitted on 12 Sep 2023
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The study isn't wrong, but it's also not right, IMO.
This doesn't seem to mention the cost of the energy, just how "efficient" it is.... which, honestly, "efficient" can imply several things, and they don't seem to clarify what (at least from my first pass of this doc).
The issue is that even if you're getting 3-4 times as much heating/cooling as you could with something else, per jule of energy potential that is put into the system (in whatever form that is), if your energy cost for that source of power is high, it's going to lose the financial argument every time.
Sure, a natural gas furnace will consume "more fuel" and produce less effective heat than a heat pump, but if you're paying 10x the cost for electricity, then you're still going to end up spending more per degree of heating than with the cheaper fuel.
Where I am, electricity is pretty cheap, but natural gas is tremendously cheaper per jule.... so we can actually pay less by using the "inefficient" fuel for our home.
I don't think the numbers are dramatically different at the end of the day, but this study seems to completely ignore the core issue that most people will be concerned with.... which is: "will this save me money?" Which is arguably the more important metric.
How would you like to define it?
How about this for an analogy - which of these two is more efficient:
Plant some wheat in your back yard, buy fertilised eggs to hatch into chickens, plant tomatoes and basil, plant an olive to grow a tree, and eventually, years down the track, you can make yourself a bowl of pasta.
Notice your next door neighbour already cooked some pasta and made more than they can eat. Ask politely and they'll just give you a serving.
Obviously - the second option is more efficient, and that's effectively what a heat pump does. They don't heat up your home, they just take a bit of heat from the air outside and move (pump) it into your home. It's far far more efficient than creating new heat from scratch with a gas system.
Exactly how much more efficient will depend on the outdoor and indoor air temperature, and on the brand/model of heat pump you buy, and other factors (such as the length of the pipe between the outdoor unit and the indoor unit). You really should ask for specific advice on your home - but in general, a heat pump is extremely efficient.
Have you actually looked into it, or are you just making assumptions?
I can tell you that my heat pump, in my house (yours will be different), in my climate, adds about $5 per week to my electricity bill. Is your gas bill less than $5 per week?
Or at least - that's how much it cost before I had solar panels. Now that I have solar... it uses about 20% of the power typically produced by the solar panels on my roof leaving plenty of excess power that we sell to the grid for about the same amount of money as what we spend buying power overnight. Since we installed solar our entire electricity bill is about $0 (and we use power for a bunch of other stuff, including to cook breakfast and dinner when the sun typically isn't shining*). We don't have a large solar system either - in fact, installing solar cost less than installing heat pumps.
(* our solar system comes with instruments and software to measure our consumption - and I can tell you that heating up a family meal with an electric cooktop uses more electricity than heating an entire house with heat pump... because the cooktop is creating heat, and the heat pump is simply moving heat)
Most of the push towards rapid adoption of heat pumps is happening in Europe, where geopolitical developments (to put it mildly) caused gas prices to spike last winter. The nature of the natural gas logistics means that different continents can have wildly different prices (unlike petroleum, where you can always throw it on a ship and send it from where it's cheap to where it's expensive), so a lot of European countries are seeing these debates play out against the backdrop of their own energy markets. Germany passed a law this year that would phase out new gas furnace installations, so that's why a lot of the debate is happening with a focus on German markets.
Whether (or how quickly) a transition to heat pumps pays for itself in euros will depend a lot on what happens in the future to gas and electricity prices.
How high, is the question. How much more is electricity where you live that heat pumps "lose the financial argument every time"? Where I'm from a kWh of electricity is roughly 2.8-3x that of natural gas, so most modern heat pumps will beat that, some by quite a margin.
If globalpetrolprices.com is to be trusted and Canadian natural gas is 0.063 CAD and electricity is 0.165 CAD you're very much in the same boat with a 2.6 ratio. Most heat pumps should be able to beat a 2.6 SCOP even in Canada.
So, sure, the study only looks at COPs and not at overall cost, but I think it's not unreasonable to expect home owners to be able to divide electricity price by gas price and compare it to the SCOP of heat pumps on offer.
Finally someone taking sense.
Asking me to compare my own bills between natural gas and heat pump is insanity, I don't have both systems installed just for shits and giggles.... but it doesn't seem to stop people from saying I should do that sort of insane thing to really know.
That site sure is interesting, I haven't dived into the data enough to know how they got the figures they did, or what it represents... but assuming they're saying that it's saying that $0.63 worth of natural gas gives you the equivalent thermal output of 1kWh of conventional electric heating (more or less)... which I think it kind of does, since, to the best of my knowledge, electric heating systems are among the most efficient at converting 100% of the energy input to heat output (or as close as we can get to that). As we know heat pumps exceed this because they're not generating heat, they're just moving it around.
Also, a blanket statement like "heat pumps should be able to beat 2.6 SCOP, even in Canada" is problematic, since Canada is huge, and some of that landmass is in the Arctic circle. To be fair, 90% of Canada's population (or something similar to that) is in the southern 10% of the landmass.... still. If we're being detailed, then such blanket statements should be avoided. A good alternative is "for the majority of the population of Canada", which is wholly accurate.
There's also other inefficiencies that aren't being considered and unless we get really deep with the information, that fact is unlikely to change; however, those inefficiencies may make heat pumps even better on paper....
There's a lot to say about this incredibly complex topic. And that's not even touching on the nuances of the word "efficiency".... since efficiency relies on specific conditions, and usually is a comparative figure. Eg, the Ford F-350 super duty is an extremely efficient vehicle, when compared to the Ford model T.... many decades of innovation will pretty much guarantee that statement is accurate. But comparing the F-350 to, say, a Toyota Prius on MPG alone, then the F-350 seems like a gas guzzling bohemouth, that's a symbol of gluttony.... Wasting so much more fuel, to travel the same distance. Both saying that the 350 is incredibly efficient and also that it's extremely inefficient, these are both true, depending on context.
There's too much nuance here that I'm just going to stop talking before I ramble myself into getting cancelled somehow.
Correct (although $0.063), and interesting to see you seem unfamiliar with this, this is the standard way of listing energy prices in Europe, it's not just that site. That site was just my first hit when I looked up Canadian energy prices. It's the low heat value and it's determined by the energy in a fuel if not allowed to condense (which is the relevant value for a traditional furnace, if you have a more modern condensing furnace you take the high heat value) and it makes it relatively easy to compare different sources of energy.
What people never realise is that being far up in arctic climates doesn't only impair an SCOP. Yeah the lowest temps are very cold, but that means temporarily bad COPs. An SCOP is made up of the whole heating period though, which in colder climates is longer, so in turn you have several months more of the time where heat pumps are extremely viable with temporary COPs above 5 or 6 saving loads of energy. The real problem is if your lowest temps are so low that a heat pump will stop working entirely, in which case you get a hybrid system or just leave your old furnace in as backup, which is even better for your SCOP because you omit the month(s) with the worst COP and only use the heat pump when it's most viable. Let's say you live in Tuktoyaktuk and heating period is basically all year, then you have your furnace on for 3-4 months but you're saving massive amounts of energy with your heat pump in the other 8-9 months of the year.
I actually tend to avoid using that term for heat pumps anyway, as it's not really correct in terms of physics. What makes heat pumps so viable is a coefficient of performance, their actual electrical efficiency isn't all that good at 50-60%, but it's also kinda irrelevant. It's sometimes easier to just call it efficiency, but like you say, once you go into the nitty gritty it falls apart.
It depends. It's certainly economically and CO2 efficient. Thermodynamically? That's something for physicists and engineers to worry about, not J. Random Bloke.
I've seen plenty of old houses over here in Germany which did have a gas furnance that was somehow under-dimensioned -- the idea is that in the real cold days you'd still have the good ole fireplace (or coal oven), as well as not so old houses which still have one because sitting in front of it.
Gets a wee bit more complicated with heat pumps and maximising the efficiency of everything as the fireplace needs to be hooked up to the heat exchanger or there won't be any hot water and modern units are closed and look rather different, but you still get a window and plenty of infrared radiation.
Then, last but not least, there's insulation. Especially up in the arctic you should be doing your darnedest to build passive houses. Certainly possible in Kiruna, I've heard that the Norwegians are trying on Svalbard.
Oddly enough I've never encountered that in Germany, I only ever see catastrophically oversized furnaces that start cycling in March... Seems to me plumbers never really worry too much about correct dimensioning, they just put the same 20 kW furnace that they know and love to install in every apartment and single family home. For some it will be somewhat adequate, for some it'll be oversized, who cares, customers never complain when the furnace cycles, but when it's too cold, you've got a problem. Same as they're never too worried about finding suitable supply water temps. Just set it to 80 and you're good, it's the customer who pays horrendous gas bills, not you lmao. That's also why everyone thinks their Altbau has to have 80°+ supply water when they have never really tried anything lower to see if it maybe suffices. My parents had their oil-furnace on 80C supply for the past 40 years and last winter when everybody was trying to save as much energy as possible they figured out you can set it to 55 as well.
I like you.
I agree, there's a lot more to it than just the argument that was presented. I am also woefully unfamiliar with measurements of energy in common use, and sort of come at things from a more physics mindset. I'm no physics major, but it just makes sense to me that way.
Personally I'm a fan of heat pumps. There's plenty of reasons not to go that route, but when it comes to electrically driven heating and cooling, you'll be hard pressed to find a better alternative.
I'm in the camp of going independent with power. Getting solar, a battery system, and converting everything to electric. That's the plan at least. If my power is free (from solar) then if I lose some efficiency in the conversation, that's okay, it's free power either way.... though, not "free".... just, I'm not paying per watt (or kWh) I just need to buy the material to make the system go.... that's not free, but day to day operations are. If I'm making sense.
I'm not where I want to be yet, everything is a work in progress for now. I still have several natural gas systems in the house, including the furnace. I can't afford to do everything all at once. My current plan is to buy and install a grid-tied solar system, with the option of batteries, in the near future. Maybe the next few years. We have a good South (ish) facing roof above our garage which will be ground zero for solar panels. It's sizeable, so hopefully 20+ kW of solar will fit.
After that's in, start working on electrification inside, make sure our grid connection is up to par, and start replacing and upgrading our furnace/water heater/whatever with electric counterparts and try to make everything as efficient as possible.
When finances allow, buy a battery system that can power the house for ~24-48h, based on usage, and add it to the solar system. Maybe start with 10-12h worth, and upgrade as we go. I'm thinking of getting the rack-mount LiFePO4 packs, and starting with around 4 (~20kWh), and go up from there. I'm an IT guy, so racks are a go to for me. As finances allow, pick up another pack to bring it to 5, and another, and another, etc, until we hit my goals. The goals are very specific and I have reasons to want 20+ kW of solar, and 2 days of battery backup. Our area supports net metering, so we should be good to start on the plan. It's going to take decades to get it done.
This is all very off topic, but I figure were so far down this thread and so deep into the bowels of post history that nobody but you and I will be reading it. I felt like sharing my plan; for no other reason than to say it out loud.... more or less.
Heat pumps are in my future. So regardless of all other factors, like "efficiency"... that's what I'll be doing. Hybrid is definitely an option, though, I'll probably go with "dual source" (heat pump + electric resistive) for my system if possible. We're pretty far south in Canada where I am (Niagara region) so I'm ok for the heat pump to provide 100% of my heating for over 99% of the year. We only occasionally get cold spikes into the -30c range for a few days at a time at most... but I'll get crucified if the inside temp drops too far (the Mrs will see to that). In the interest of electrification, I'm hoping to get a resistive electric heating system for the alternative heat system. It's not as "efficient" as the heat pump, but when the heat pump won't work because of the extreme cold, it's the next best thing IMO.
I want a battery system because I don't want to be down if the grid goes away, and I want enough battery that we don't have to rush onto the roof every time it snows, to clear the panels else we need to run on grid power.... having some leaway in how much time we have to deal with the problems that might prevent the system from working, will be perfect.
What's also interesting is that you have to factor in the costs and CO2 emissions of the fuel source and it's delivery method. A new building code for a county in my area was adopted which requires calculations for energy efficient HVAC systems and also CO2 emissions with those systems. Surprisingly, natural gas has less CO2 emissions associated with it, while electricity is 2.86 times as much. This is because grid electricity is mostly produced by fossil fuels, then needs to be delivered to the site but there are many losses along the way. So even if the all electric equipment is twice as efficient as the equivalent natural gas equipment, it still contributes more CO2 production. This is part of the issue with phasing out natural gas and moving to all electric in its current state. But with that is the push (and requirements) to produce energy on site and shift towards net zero energy for commercial sites, which is definitely better than using grid power from an emissions standpoint.
It also doesn't add up if you're getting twice the heating per joule of input if you can only input a quarter the number of joules as your source is limited.