Heat Pumps – The Well-Tempered Future of A/Cs • Hacker News Board

Re: Heat Pumps – The Well-Tempered Future of A/Cs

#321

Post by notyourwork » Thu, Jul 06, 2023, 4:48 AM UTC

superq wrote: post #311

notyourwork wrote: post #303

Earlier quoted context omitted.

Not sure if it's a bit over-priced, however, we replaced a gas furnace without A/C. The variable speed air-handler is amazing for constant low speed circulation and the energy savings with moderate temperature for 60-75 degree weather is incredible. Also, I have 15k BTU available for one or two additional head units. I opted for this approach instead of under-sizing the heat pump or assuming we'd need the extra head…

Your temperature controls are dependent on a "Kumo" cloud? that's rather terrifying. What if your internet goes out, or what if the cloud gets attacked (or your smart device)? Does that mean you lose control of your climate control?

Did I ever say they are dependent on Mitsubishi's Kumo cloud? No.

Re: Heat Pumps – The Well-Tempered Future of A/Cs

#322

Post by crazygringo » Thu, Jul 06, 2023, 4:51 AM UTC

punkybr3wster wrote: post #299

post_break wrote: post #27

When my AC finally needs replacing I'm going heat pump, and then also ditching my gas water heater. The constant fees of a gas line are ridiculous at this point and any more electricity usage will be offset by the 9 months of the year I'd never turn on the heat.

Now you can even get water heaters with heat pumps and combo units that dump your waste heat from your hvac heat pump into the water heater. It’s wild.

Your AC powering your hot water heater at the same time... that's genius.

Re: Heat Pumps – The Well-Tempered Future of A/Cs

#323

Post by jay_kyburz » Thu, Jul 06, 2023, 4:55 AM UTC

punkybr3wster wrote: post #299

post_break wrote: post #27

When my AC finally needs replacing I'm going heat pump, and then also ditching my gas water heater. The constant fees of a gas line are ridiculous at this point and any more electricity usage will be offset by the 9 months of the year I'd never turn on the heat.

Now you can even get water heaters with heat pumps and combo units that dump your waste heat from your hvac heat pump into the water heater. It’s wild.

When we put the solar on the roof we bundled in heat pump hot water system as well.

It's timed to only use power right in the middle of the day when the sun is shining, and in the middle of the night when power is cheap. (needs both because the tank is fairly small and my kids like long showers)

Re: Heat Pumps – The Well-Tempered Future of A/Cs

#324

Post by staplung » Thu, Jul 06, 2023, 5:13 AM UTC

nsxwolf wrote: post #193

When I needed a new air conditioner a couple years ago I was quoted $17,000 for a heat pump. I can only guess at that point whatever energy cost savings it would bring would never be realized within the service life of the system. I went with a $6000 standard replacement AC unit.

Might have been what I call a "fuck off" quote. That is, the people who gave you the quote didn't really want to do the job (too small, inconvenient location, or who knows what) and so quoted you an outrageous price figuring you'd either decide not to do it or if you did, you'd end up paying enough to make it worth their while. Happened to me a few years ago when I needed to re-tar my roof. The first guy quoted a figure that was like 4x what the next guy quoted.

Re: Heat Pumps – The Well-Tempered Future of A/Cs

#325

Post by [deleted] » Thu, Jul 06, 2023, 5:21 AM UTC

triceratops wrote: post #122

wcfields wrote: post #55

Earlier quoted context omitted.

Have to imagine that the niche market for making 40F/4C "cold" water from luke-warm tap water (if you live in an area that is so hot the tap water is warm) is fairly small.

It's not a niche market. Every office in the world has a water cooler. The market for evaporative water coolers is niche, or probably only big in the developing world. Other than that water coolers use refrigeration aka a heat pump.

[deleted]

Re: Heat Pumps – The Well-Tempered Future of A/Cs

#326

Post by vladvasiliu » Thu, Jul 06, 2023, 5:24 AM UTC

manmal wrote: post #306

mft_ wrote: post #305

Earlier quoted context omitted.

Our house (in Europe) is relatively old and not well insulated by modern standards, and all of the advice we read and receive from experts is that heat pumps are not a good fit without additional insulation. The gist is that we’d need to spec larger units and/or run them harder than usual, removing savings vs. gas.

Isn’t insulating a house way more expensive than buying a bigger heat pump and paying for extra electricity?

It probably depends on what kind of insulation work needs to be done.

My parents' house in France is one of those hundred-year-old stone ones. It's fairly cool in the summer, but it gets quite cold in the winter. My father did the insulation work himself (he's not in construction) for fairly cheap and saw his gas bill halve.

Re: Heat Pumps – The Well-Tempered Future of A/Cs

#327

Post by kelnos » Thu, Jul 06, 2023, 5:38 AM UTC

Alupis wrote: post #135

kibwen wrote: post #131

Earlier quoted context omitted.

It's actually difficult to say what the cost would be if everyone switched over. The reason is that natural gas is subsidized, both on the production side (at least in the US, which wants energy security) and on the consumption side (because it's politically unpopular to let people freeze to death). Of course, electricity prices are also affected by subsidies. Figuring out the true operating prices would require some…

It seems to me, there is no future where a heatpump can be the only source of in-home heating then. 1) Natural Gas is vastly cheaper in most/all of the US. 2) Homes still require an alternative heating source when temperatures drop to low levels (coincidentally when people need heating the most). So, even if a heatpump is technically more efficient in terms of emissions, the technology does not solve all of the probl…

You can also use resistive heating (like baseboard heating or space heaters) as a backup for the heat pump when it's too cold out. They're expensive to run off the grid, but if you have solar power and battery storage (for operation at night), they're essentially "free".

Obviously you wouldn't install solar panels and a battery just for this, otherwise it's very much not free, and probably a lot more expensive than burning gas. But if you already have the solar+battery install, and have enough capacity, it could even be cheaper to operate than a gas furnace.

Re: Heat Pumps – The Well-Tempered Future of A/Cs

#328

Post by kelnos » Thu, Jul 06, 2023, 5:42 AM UTC

bluSCALE4 wrote: post #143

Alupis wrote: post #128

Earlier quoted context omitted.

People's AC summertime electric bills regularly get into triple-digits - it's not uncommon to hear someone with a moderately sized home having a $200-400 electric bill in the summertime. However, even in the midst of winter, gas heating bills rarely climb above $100 monthly. What am I missing here? It seems a heatpump, while more efficient, will cost significantly more to operate. Natural Gas is cheap ... and clean e…

I'm with you here. I replaced a gas water heater with a hybrid water pump and I'm paying more for my troubles. The thing is, I do plan on installing PV panels in a few years--I can't generate my own gas so once I make that happen, I'll be a happy camper.

That was my plan; install solar panels and then slowly switch things from gas to electric as they need replacement. Unfortunately solar installer I was in contract with canceled on me for seemingly-bogus reasons, and I didn't have time to find a new one before California's new, unfavorable net metering rules went into effect.

Re: Heat Pumps – The Well-Tempered Future of A/Cs

#329

Post by kelnos » Thu, Jul 06, 2023, 5:47 AM UTC

pdx_flyer wrote: post #152

I was looking for a whole home heat pump and got some quotes that started at $27,000 for a home that is 1800 square feet. That price is a bit hard to swallow. I really don't want to just cool one or two rooms in the house.

This kinda sounds like the installer had a queue of much larger / more lucrative projects to tackle, and quoted you a high price to get you to go away... or pay the ridiculous price and make it worth their time.

A decent heat pump sized for that square footage should cost well under $10k, and it's pretty unlikely your house would need so much work to install it that the labor involved could make up for the rest of that quote.

Re: Heat Pumps – The Well-Tempered Future of A/Cs

#330

Post by callalex » Thu, Jul 06, 2023, 5:49 AM UTC

Turskarama wrote: post #266

ori_prior wrote: post #245

Earlier quoted context omitted.

Your numbers are off. Thermal power plants typically do have a thermal-to-electric efficiency of around 30% (40% max), so with your heatpump having an electric-to-thermal efficiency of an assumed 300%, you end up with basically no difference in CO₂ emissions. Note that there are some misleading efficiency claims for gas plants around 60%, but those are not for thermal-to-electric efficiency but for generating electri…

Keep in mind that pure gas heating is also not 100% efficient because you need to remove the exhaust, meaning you need to use a heat exchanger and no heat exchanger is 100% efficient either. Some of the heat gets carried outside.

Sure but these days even the cheap stuff is around 95% efficient because that enables the use of cheaper plastic exhaust pipes instead of insulated metal.