371–380 of 766 posts
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All modern furnaces I've seen take #2 - use air from outside. Despite that they can get to 99% efficient. It doesn't take much energy to heat up that cold air.
My experience in the US at least is that its not uncommon for the furnace air intake to draw air from inside the house (my last two homes in PNW as one example).
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Right, the heat pump will reduce energy use to maybe 1/3 of a gas furnace, but natural gas is something like 6x cheaper for the same amount of energy, so it is an expensive folly. If California is serious about this, they need to reign in the utilities to reduce prices and or stop the attacks on solar installation.
In the continental US you get ~2x the heat from burning natural gas in a combined cycle turbine to run a heat pump than you would from using a high efficiency gas furnace. The market price of electricity vs gas varies quite a bit through time and various distortions of the market. Currently gas is cheap, but you want to compare historical averages when buying something that lasts 15+ years not simply look at current…
Combined cycle is like at most 70% efficient, subtract 10% of distribution, you end up with 60%.
At 50f my 5T heat pump takes 6.6 kWh to generate 50,000 BTU.
6 kWh of energy takes 71cf of gas to make - accounting for transmission and generation losses.
71cf of gas will make 71,000 BTU of heat, assuming an 80% efficiency furnace, that comes out to 56,000 BTU usable.
Yes a heat pump will vastly outperform resistive strip heat - but not even an 80% gas furnace.
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> It's now more expensive to fuel a vehicle with electricity than gas This is very hard to believe, what are you paying for electricity? California gas prices are also way above the national average at the moment. Here's a per-state comparison from last year, I'm sure it's a bit out of date but I doubt things have completed flipped in a single year: https://energyinnovation.org/2023/07/27/ev-fill-up-savings/
PG&E is 62 cents/kwh for peak rate above-baseline, I believe 52 cents/kwh for off-peak (which most EV charging would be). Gas prices where I'm at are around $4.20/gal. I ran the numbers for my Mazda CX-90 PHEV SUV, which gets about 1.7 mi/kwh on electric and about 23 mpg gas. It's about 30 cents/mile on electric and about 18 cents/mile on gas. For this tank only I have been charging at home (and at work, and anywhere…
https://www.pge.com/en/account/rate-plans/find-your-best-rat...
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... what do you think real ac is?
https://www.thisoldhouse.com/heating-cooling/reviews/heat-pu... "Heat pumps use refrigerant to condition the air in your home by adding or removing heat through thermal exchange." "Air conditioning is a cooling system that circulates cool air into an enclosed space, creating a comfortable atmosphere and improving indoor air quality." "Air conditioners generally last longer than heat pumps because air conditioners onl…
This is what air conditioners do, too.
> "Air conditioning is a cooling system that circulates cool air into an enclosed space, creating a comfortable atmosphere and improving indoor air quality."
This is what heat pumps do, too.
These are two sentences that describe the same process, just in different words.
The last quote is potentially relevant: a heat pump is an air conditioner that can run in reverse to provide heat in the winter, so you're running it in both situations, and thus for more time.
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I live in the Bay Area California and get electricity from PG&E. I use a minimal amount of electricity and I paid 43 cents/kWh last month. Gas from Costco is $4/gal right now. I have a plugin-hybrid which does 4miles/kwh and 45mpg or in terms of money: 9.3miles/$ on electricity and 11.25gas-miles/$ on gasoline. But maybe you don't actually care about fuel efficiency, then you have an argument that it's cheaper to fue…
"I paid 43 cents/kWh last month" I live in the Bay Area as well and I have an EV (2015 Fiat 500e), and am on the PG& Home Charging EV2-A plan. I charge my car between 12am and 3pm and pay $0.28/kwh, 29kwh/100 miles and I should be getting about 12.3miles/$.
I but about $700/year in gasoline. And pay about $600/year insurance. And drive about 6500 miles a year.
So insurance and gas are both about 10 cents a mile. I think depreciation and maintenance are higher at about 15 cents/mile. So 50 cents a mile. IRS says a business can write off 67 cents a mile.
Better late than never but it’s a shame…
In the UK we have poor insulation, noise concerns (dwellings very close together), high electricity rates, periods of sub zero temperatures in winter and from what I can gather a lack of skilled fitters in this space.
All together it doesn’t make a convincing argument
Plus all the comments here about broken systems, high electricity costs, inadequate temperatures etc doesn’t fill me with hope
Yes I’ve heard every rebuttal (“but Nordics”, “your fitter was bad”, “you under specced”, “you over specced” etc)
Building code should have solved insulation issues decades ago. Heat Recovery systems etc instead of relying on drilling holes in to window frames as the primary source of ventilation
I hear a lot of horror stories on HN every time the subject of heat pumps comes up. Things like high costs, units not defrosting properly in winter, etc. Most of these stories tend to be for central air conditioning units. I think that mini-splits could be a much better introduction to heat pumps for a lot of folks. They are cheap, easy to install, and the units in my house have been running 12 years as our only sour…
Either I have some magic heat pump or a lot of the horror stories are overblown or based on using out of date technology.
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Ground source heat pumps are available that go down significantly lower than 30F. They are more expensive. Though running the electric wires is also very expensive due to their inefficiency. Typical heat pumps are often better suited for warmer climates because of this It also appears that the tech for the more typical air source heat pumps has improved significantly in recent years which makes it more viable for col…
I believe they run a heat conductive fluid through heat exchange coils in the ground. This allows you to pump heat into the ground during winter and extract said heat (not sure how accurate this is) during the winter.
If above ground ranges from 0-100 degrees F, underground likely ranges from like 64-68 degrees F, which makes it really energetically "cheap" to get to your preferred temperature range, heating to idk 70 at most and cooling to probably not even 65.