SynbiosVyse t1_izrzbsk wrote on December 11, 2022 at 12:16 PM

Reply to comment by THINKFR33LY in Holy $#!^ Eversource by Xaphas

I'm so tired about hearing about how wonderful heat pumps are. I have both a brand new ducted central heat pump from Bosch and a gas steam boiler, each for different areas of the house. The area that the heat pump serves is half the size and the bill last month was $150 (on top of normal electric usage). Gas bill was $100 and that includes domestic hot water too which is served by the boiler via indirect.

Here's the icing on the cake: the gas boiler cycles between 68 and 64 (night) and the heat pump is set to 64 all the time. It just can't keep up. I'm really regretting my heat pump now. It's only going to get worse in the colder months coming up.

mp246 t1_izxilpk wrote on December 12, 2022 at 4:14 PM

there are so many variables that go into your situation, never mind anybody else's, it's completely useless to look at a $150 electric bill and $100 gas bill and draw any kind of conclusions, other than you have no idea what you're talking about. hur dur heat pump bad is basically all you're saying.

SynbiosVyse t1_izxkno8 wrote on December 12, 2022 at 4:28 PM

They are bad in cold weather. You can't argue the physics of it. If you look at the efficiency curves the top of the line Bosch drops to 50% efficiency below freezing. I'm not sure what variables you speak about, this is a fairly controlled experiment. Mini splits are about 30% more efficient than central heat pumps so I could see those being more desirable. I think the longstanding conception that heat pumps suck below freezing is true. It's blowing cold air for first 15-20 minutes of the cycle and never really gets up to the temp that the furnace did. It needs to run for a long time just to raise one degree. I understand they're designed to run more frequently than a furnace for more air circulation but it's using more electricity as a result with the condenser and fan running. It's just a stupid appliance unless you have solar or cheap electricity. I don't see how anyone is expected to save money with this thing.

For clarification it was $150 on top of average electricity bill so approximate cost just to run heat pump.

mp246 t1_izxm2ql wrote on December 12, 2022 at 4:37 PM

>They are bad in cold weather. You can't argue the physics of it. If you look at the efficiency curves the top of the line Bosch drops to 50% efficiency below freezing.

you really don't know what you're talking about. i can't find a bosh specific chart, but modern heat pumps can be ~200% efficient at 0F. and i'm talking about efficiency in the sense of units of energy in = units of energy out, not in a sense of dollars per BTU or whatever

>I'm not sure what variables you speak about, this is a fairly controlled experiment.

you really, really don't know what you're talking about.

SynbiosVyse t1_izxscp8 wrote on December 12, 2022 at 5:18 PM

The marketing of COP (coefficient of performance) being greater than 1 for heat pumps is exactly the kind of marketing they want you to believe as being important. COP is a good way to compare heat pumps to other heat pumps, since standard energy-in/energy-out doesn't make sense. If you're talking about relative efficiency, central heat pumps are going to drop to about 50% in terms of the amount of electrical power they use for the amount of heat they produce. For example, if it uses 2 KWh to raise 1 degree from 54 to 55 F, it will use 4 KWh to raise 1 degree from 10 to 11. Because of this sharp decrease in efficiency you're going to be paying up the nose in electricty compared to a furnace or boiler which efficiency curve is completely agnostic to the temperature outside.

mp246 t1_izxu5y8 wrote on December 12, 2022 at 5:30 PM

everybody already knows it takes more energy to heat something as it gets colder and colder outside dude. and you still don't understand the difference between relative efficiency and absolute efficiency, you keep mixing them up, and then on top you that you mention absolute costs when i specifically called out the difference in the previous post.

when you talk about your gas boiler vs your heat pump, what does it cost you, in terms of dollars, to get 1 degree of rise out of each? post that, along with the manual j for the respective heating zones, and then we can start to get a rough idea of what is more efficient in terms of absolute costs. until then, you're just talking out of your ass