Why Heat Pumps Are Immensely Important | Hacker News Reader

Why Heat Pumps Are Immensely Important

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58 pointsherbstein23 comments

If you pair a heat pump with good insulation, the effect can be quite staggering. My parents moved into a new house 6 years ago and their annual heating bill (for space and water) dropped from ~2500EUR down to around 300EUR.

This is in an area where night-time winter temperatures hover in the -5°C range, occasionally dropping to -10.

The old house was around 30 years old, with fairly thin insulation (5 or 7cm was pretty standard back when it was built), and had an oil burning furnace for heating.

That can’t be right.

From 2500/yr to 300/yr is 88% reduction in cost.

Heat pumps are 300% - 500% efficient, enough to represent a 66% to 80% savings on their own. Adding insulation reduces the total amount of heating necessary, plus heating oil and electricity aren't priced the same per-unit of energy.

This is not unbelievable in the slightest. Perhaps if you find it surprising, you should ponder where your reasoning got hung up.

Yep, the "magic ingredient" is definitely insulation (along with triple pane windows).

I’ve looked at ground heat pumps before (not air pumps). However they are a huge capital outlay of £10k-£19k ($13k-$26k).

Both air and ground heat pumps work best for buildings with underfloor heating. Floors cover a much bigger area than radiators so they don’t need to get as hot to provide the same amount of heat.

We’re in a 70 year old building so that doesn’t help.

The savings are minimal maybe £30-£60 a year before the recent gas price increases. You can get grants of £2k per annum for 7 years so you will get money back. However they don’t really save any money unless you think gas prices will remain high. Outside of that you do it to be green.

https://www.which.co.uk/reviews/ground-and-air-source-heat-p...

Air source heat pumps that couple to forced air venting work great as well. The Mitsubishi Zuba line up is an example. Of course better insulation is needed reap any benefits.

Good video. I've been thinking about heat pumps a lot lately, namely, is it possible to make geothermal ground loops cheap and not disruptive? I wrote a bit about it here: https://www.greennewdealio.com/heating/robot-mole/

Air source heat pumps really are great and it seems everyone in mild climates should be moving towards them. In fact, what I'm working on right now is trying to figure out the maximum ground loop "budget", beyond which it would be cheaper to run inefficient heat sources (COP of 1) for the small periods of time where air sourced pumps no longer work.

I looked into air-to-water heat pumps (hard) as I’m planning to replace my boiler this summer.

Even with large cast iron rads, I need 130°F water temp when it’s below about 25°F outside and the air-to-water heat pumps struggle to hit 125°F output water temp there and fall even lower when it gets colder.

They aren’t in all markets but there are heat pumps that use CO2 as the refrigerant that can make quite-high output water temps. They’re often used for domestic hot water. I haven’t looked too deeply in to them but IIRC they have COPs around 3–4. Sanden is one manufacturer, Mitsubishi and their Ecodan line is another.

Would it be possible to do multiple vertical shaft tubes, straight down rather than a huge flat thing?

I feel like in 100 years time we'll have all these loopy pipe arrays all over the place being a pain to clean up...

Yes, this is usually how it's done when a large field doesn't happen to be available. Vertical boreholes are much more expensive to make than shallow trenches, though.

Depends on what your ground looks like. If it's bedrock at the surface and you'd have to dynamite to clear a large patch, then drilling a small hole will be much less expensive and much more efficient.

If it is just plain brown dirt for miles down, then digging some trenches might be a better solution.

If it's a few feet of sand until you hit the water table, then I have no idea what the best solution is.

The Bay Area has a mild climate but I’ve never seen a heat pump here.

Probably because in a mild climate even conventional heating systems don’t cost much. There isn’t a lot of pressure to invest more in the system initially just to save only a small amount per month.

The heat pump has more to do with getting off gas and oil and other hydrocarbons that are burned at the house, and switching all your energy usage over to electricity, which can either be efficiently generated elsewhere, or allow you to go completely off the grid.

Don't do it today to save money today. Do it to save the planet and help ensure that you're not beholden to $9000/hour bills because the people selling you the precious hydrocarbons have you backed into a corner that you cannot possibly dig yourself out of.

You know, so like you can't be screwed by the like of ERCOT when they tell Texans "oh, that sure is a nice grid you've got there. It would be a real shame if it were to be shut down simply because some of the electrical generating plants haven't been properly weatherized. Hmm, I wonder how many of these plants we should take offline on the coldest day of the year????"

As someone who has lived both in New Zealand and Australia where both countries mostly have heat pumps in every house - I'm genuinely surprised to hear that many people in other countries don't all have them. They're relatively cheap to install ($1500-$4000), safe and efficient.

What is your energy cost? $/kWh?

If electricity is expensive, the payback period can take longer for residential/commercial applications.

Around 22c/kWh on over over the last month.

While not German-levels of electricity prices, that's still 100% more than my elec price in the US and comparatively worse than gas . Retrofitting a heat pump for me is a negative NPV investment.

> in New Zealand and Australia where both countries mostly have heat pumps in every house

I'm not sure that's right. I've lived in a lot of houses and units in Australia, in city and country, and none have had air conditioners, assuming that's what a "heat pump" is. The houses I've stayed in in NZ didn't have them either.

[After googling what a heat pump is] I didn't know a heat pump is a thing, like an air conditioner but can heat as well. I don't remember ever hearing about them! (I'm 50)

Really! That's interesting. I'm 34, and from memory (which might be a bit rusty) of the 6 houses I've lived in in NZ 4 of them had heat pumps (aka split system aircon), and in Australia I've lived in 4 houses and all of them have had them.

Two years ago I moved to a house with only a fireplace for heating. I spent the first winter taking care of the fire, which is nice at the beginning but a real chore after a while.

Before this winter I installed a air to air heat pump. The first thing I learned is that everyone calls that differently, to the point that talking with companies to get one installed was difficult: "-Hello, I'd like a heat pump please. -Sorry, we only do AC.". The name people give to this device really depends on the area.

I went with a single console unit, basically a 1x1m square that hangs inside on a wall close to the floor like a radiator. The installation took a day and costs about 2000€.

On the coldest days of the year when the temperature stays around -15°C, the unit uses about 25kWh of energy for a day to heat the whole house at 19°C. About 15kWh on days when the temperature stays around -5°C.

Before next winter I'm planing on having someone check if there are quick wins regarding insulation, I suspect that some of my windows are pretty terrible.

i want to get a ground heat pump, there is common to have a bore well in our area that we can get fresh water out of. i want to know if there is a calculator or something that would tell me if its possible and depths/temperature i can expect out of the system..

i already have 5 kw solar setup and expecting to install 200-300Litre solar water heater but a ground heat pump should be useful in winters when the sun is out and electricity gets out.

currently we have 0 house heating, we only use insulation and personal heaters to warm bodies so if i could have a ground heat pump get the house temperature up, that would be great

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