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Comment by retrac | Hacker News Reader

> it seems crazy that I warm the air of my house and then use electricity to keep the fridge cooler than the air I just heated

The fridge is simply moving a little of the warmth in your room out of its box, and adding a little more warmth to the room in the process. You lose no heat from the room, which is what matters, really. It would be worse to dump the heat outside! At least in winter. The heat has to be removed in summer if you have air conditioning.

In any case, an exterior heat exchanger and heat pump that can handle a wide exterior temperature is much more heavy duty. This could all end up being less efficient, in practice. House-scale heat pumps can efficiently move heat even from a freezing cold outside into a warm interior. Just as fridges can efficiently move heat from their cold interiors to a warm room.

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I always joke that in winter all appliances are 100% efficient (I know they're not). Some look at me funny but the ones who pay the gas bill get usually get it.

And incandescent light bulbs!

No, because the light can escape through windows.

So can heat. That's not the appliance's fault.

It's not about fault at all - I'm just saying that the analysis does not apply to lightbulbs. For a lightbulb to be as efficient as a resistance furnace at heating a room, you would need to have zero light escape that room so that all the light would be converted to heat. Then, the heat would leave the room at the same rate as heat generated by a resistance furnace.

Even if we consider incandescent light bulbs, which waste most of the energy they use as "heat", that heat is actually being transferred primarily through radiation, so it can escape through windows more easily than the heat that a furnace transfers to your indoor air.

Thermal infrared doesn't go through glass. You only lose a negligible amount of visible light. It's still 100% efficient as an integer percent.

I assume by “thermal infrared” you mean the IR produced by approximately room temperature objects. Incandescent bulbs produce much higher energy infrared because the filament reaches about 2000 Celsius. Those higher energy waves can go through glass.

Right, that's true, I was thinking about it wrong.

Still, not much is going to hit a window on average. So maybe 90% efficient.

You do realize that burning natural gas for heat produces light as well right?

Natural gas furnaces are designed to not let that light out. Instead, the light is absorbed by the surfaces of the furnace and turns into heat. The inefficiency in gas furnaces is heat leaving in the exhaust.

Resistive heaters lile a lightbulb are much less efficient than a heat pump. You'd still be better off with the led.

The heat isn't where you want it.

This is the first year where heating the home with gas isn't an order of magnitude cheaper than with electricity here in the Midwest. Gas still wins, but not by as large of a margin!

“100% efficient” doesn’t tell the whole story of the gas bill if you’re heating your house with something cheaper than electric heat (e.g. natural gas).

If you have a resistance electric furnace, that is essentially true. With gas, you add the electric generation and distribution losses, which is a pretty big difference. It does cost more to run an appliance than to heat with gas.

Gas boilers produce NO2, and other nasties - they do affect air quality in your house

How do they affect the air quality indoors? Don't modern (less than fifty years old) gas boilers have balanced flues so that they take in air from the outside and exhaust the combustion products outside too?

Surely properly installed gas boilers always did that even without balanced flues too.

My experience (sample of one) is that they don't. They're supposed to, but VOCs are definitely higher all winter running heat than all summer running air conditioning. Natural gas combustion is at best _mostly_ exhausted.

It could also be that outdoor AQ is worse around you in the winter because everyone is running their boilers, and then that outdoor air ends up inside. I can't test it because I have a heat pump, but I would be curious to know what happens to your VOCs if you turn off your boiler at a time when your neighbors are still running theirs.

My meter here in boulder, CO reads effectively 0 VOC outdoors all year round.

> My experience (sample of one) is that they don't.

There is something very very wrong with your equipment (or you're measuring something else not having anything to do with the heating equipment - more likely). A high efficiency furnace has a sealed combustion chamber, the entire thing runs in a circuit vented to the outside - combustion air comes from the outside and it is vented to the outside. If it is not airtight sealed from the indoors, it is broken. Even a mid-efficiency furnace with a non-sealed system will vent 100% of the flue gas outside.

> Natural gas combustion is at best _mostly_ exhausted.

Bullshit for any modern equipment (ie installed in the last 50 years).

At least where I live in the US if you want a ventless natural gas heater you can just go buy one. It's not something I'd recommend.

Mid-efficiency furnaces are still commonplace in the US, and they don't have sealed combustion systems - they get combustion air from the indoor space, but they vent 100% of combustion products out. High-efficiency furnaces in the US made in the past 30 years or so use sealed combustion with intake and outtake to the outside. (North American high efficiency furnaces older than about 30 years were not necessarily sealed).

But yes, the GP is full of shit. Maybe they have some other non-induced vented gas burning appliance (ie a hot water heater or gas hob), or their measurement equipment is faulty.

> But yes, the GP is full of shit.

Or you live insulated from shitty alliances and low income life.

A friend's husband was killed by a faulty boiler, carbon monoxide poisoning. In 2015 I lived in a house where boiler ignition didn't work and you had to reach inside with a lighter. That unit was definately not sealed.

UK only required consenser boilers since 2005, the ones before that used to air from inside your house.

Condenser boilers and balanced flue are separate concepts. The house I bought in 1978 had balanced flue gas heaters but they were not condensing. Condensing boilers are an efficiency measure. Balanced flue boilers have been available in the UK since the mid sixties.

All I can do is share personal experience of living in rental properties in UK, and if these boilers were really sealed, my acquaintance wouldn't be dead.

Whether most boilers are prehistoric, or it's just years of neglect, I don't know.

If you account for the electric generation and distribution losses, you should do the same for gas.

"It does cost more to run an appliance than to heat with gas."

That's highly dependent on the appliances involved and the price you pay for each fuel. For me, a heat pump is much cheaper to run. You really need to calculate it for each individual situation.

Heat pumps and electric furnaces are not the same thing

But if we're going with the "heatpumps are more than 100% efficient" that everyone brings out, then running my computer to work & heat my room is far above 200% efficiency.

If I'm running my computer to use it & it keeps me warm, there is no way turning on a natural gas heater is going to reduce my costs.

Heatpumps are more than 100% efficient refers to a technical specification measure called efficiency, which is watts of heating per watt of energy input. For space heaters, electric furnaces, and your computer (/many other appliances), it’s always 100%. For modern gas furnaces it can be 90%ish (but the difference in electricity and gas prices mean that gas furnaces are still cheaper). For heat pumps it’s typically between 200% and 540%.

If you have a thermostat in your home, any appliances you use will reduce your heating usage because the thermostat will automatically decrease how much the furnace runs. So, yeah, it’s not wasteful to vent your computer exhaust outside in the winter, but no one’s doing that. On the other hand, it’s not worth it to run appliances you wouldn’t otherwise run unless you have an electric furnace, in which case it doesn’t matter.

> So, yeah, it’s not wasteful to vent your computer exhaust outside in the winter, but no one’s doing that.

Uh, come again? If I am using my computer anyway - why would I exhaust the waste heat outside if I have to heat the indoors anyway? That is wasteful.

Oops I meant to say it is wasteful - typo

Sure but why limit ourselves to "which is watts of heating per watt of energy input." Wouldn't "amount of useful work per watts of energy input" be OK? So if I am putting in 100 watts constantly to my PC I am getting 100 watts of heating & 1 unit of computing. Which is more than 100%

It's always been funny to me that throughout engineering people chase like 1% efficiency improvements from like 20 to 21 or 35 to 36 and it's usually a big win when achieved... meanwhile resistive heating has an efficiency of 100% and it still manages to absolutely suck.

It only sucks because of generation and transmission losses. If those didn’t exist (not possible), electricity would be much cheaper and they would be on par with or better than natural gas furnaces

Of course, by the same token, in summer their efficiency is less than you expect since you need to consider the additional burden on your AC.

I think 100% is pretty accurate for most devices, except for washing machines and other gadgets connected to the sewer. Where else would the energy go?

Your fridge has the potential to go even higher than 100%, as it's a heat pump. But for more than a temporary effect you'd have to keep replacing the stuff inside it with stuff warmed up to outside temperate, which would have to be between fridge temperature and room temperature. Perhaps slightly impractical.

Get buckets of water from your pool (or lake or well) and put them in the fridge till they cool down. Then dump the water outside and get a new bucketful). To save effort you could run 2 hoses with a small pump. You are now heating your house with a ground source heat pump.

I really enjoyed reading The Homemade Heatpump Manifesto on Ecorenovator. https://ecorenovator.org/forum/showthread.php?t=484

In the summer, my heat pump water heater in the basement is essentially 'free' to run, since most of the heat it captures is by condensing water in the air i.e. dehumidifying my basement. I still need a dehumidifier, but it doesn't have to run as hard.

The back of my fridge is in a really confined space, like many fridges - that heat would be better taken somewhere else.

The smart thing to do in winter is put municipal liquid water in your freezer, and dump it outside once frozen to thaw in spring. Rince repeat all winter long.

Voila: everyone has heat pump heating! (And dead compressors).

The dumb thing is having the compressor itself indoors in summer. Should be outside.

Interesting, how to remove it easily from the container? Or do you use an ice machine? Is this more efficient than using the heater? Guess it uses heat pump tech.

Just have tubs of water. Dump them once they’re ice.

Yes, more efficient than a resistance heater. Possibly more cost efficient than gas.

Wastes a lot of water (if you don’t have a well).

A fridge is just a heat pump.

The issue with that is that if it’s outside, you need a hole in the wall somewhere to connect it.

Today fridges are more or less plug and play. Most kitchens don’t have a hole in the wall going outside where the fridge would go. Some kitchens aren’t even on walls facing the exterior (which I dislike, but they exist)

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