Heat pump water heater during the winter

mincus · 01-16-19, 11:57 AM

Hi all!

I have a heat pump water heater in the basement and absolutely love. Had it for about 5 years. Obviously I want to keep it in heat pump mode as that uses the least amount of electricity. In the summer it has the added benefit of cooling and dehumidifying the basement. A win win.

However, my question is what to do during the winter. Should I keep it in heat pump mode, or electric resistance? Heat pump mode will use less energy to heat the water, but also takeup heat from the basement that then theoretically needs to be replaced by my furnace.

I know there's a lot of factors to consider. We do heat the basement somewhat, but not much. I have three vents open down there just to keep the air moving and keep it from getting too cold. We have heat pumps for our main furnace.

Any thoughts?

Thanks!

NiHaoMike · 01-16-19, 09:27 PM

Just leave it in heat pump mode.

jeff5may · 01-17-19, 03:03 AM

What Mike said. The actual heat transfer depends on a lot, but since you have forced air heating, you're not going to be wasting power. Heat rises, so your forced air will stratify above what comes from the water heater. The cold air from the water heater will drop to the floor and cancel out some of the heat loss through the basement floor. If anything, you will be robbing some energy from the forced air system to heat water. Since this heat came through another heat pump indoors, you're not wasting power.

u3b3rg33k · 01-17-19, 03:10 AM

I think there's a DoE study that shows the impact of a HPWH is pretty minimal, even on homes heated by a heat pump, and that it was decisively preferable to any version of "exhausting the cold air outdoors" or running in resistance mode.

mincus · 01-18-19, 01:41 PM

Ok, this is what I've been doing, but always been curious as to what's best. Thanks all for the answers!

01-16-19, 11:57 AM	#1
mincus Helper EcoRenovator Join Date: Feb 2009 Location: St. Louis, MO Posts: 42 Thanks: 0 Thanked 0 Times in 0 Posts	Heat pump water heater during the winter Hi all! I have a heat pump water heater in the basement and absolutely love. Had it for about 5 years. Obviously I want to keep it in heat pump mode as that uses the least amount of electricity. In the summer it has the added benefit of cooling and dehumidifying the basement. A win win. However, my question is what to do during the winter. Should I keep it in heat pump mode, or electric resistance? Heat pump mode will use less energy to heat the water, but also takeup heat from the basement that then theoretically needs to be replaced by my furnace. I know there's a lot of factors to consider. We do heat the basement somewhat, but not much. I have three vents open down there just to keep the air moving and keep it from getting too cold. We have heat pumps for our main furnace. Any thoughts? Thanks!

01-16-19, 09:27 PM	#2
NiHaoMike Supreme EcoRenovator Join Date: Oct 2008 Location: Austin, TX Posts: 1,154 Thanks: 14 Thanked 257 Times in 241 Posts	Just leave it in heat pump mode. __________________ To my surprise, shortly after Naomi Wu gave me a bit of fame for making good use of solar power, Allie Moore got really jealous of her...

01-17-19, 03:03 AM	#3
jeff5may Supreme EcoRenovator Join Date: Jan 2010 Location: elizabethtown, ky, USA Posts: 2,431 Thanks: 431 Thanked 619 Times in 517 Posts	What Mike said. The actual heat transfer depends on a lot, but since you have forced air heating, you're not going to be wasting power. Heat rises, so your forced air will stratify above what comes from the water heater. The cold air from the water heater will drop to the floor and cancel out some of the heat loss through the basement floor. If anything, you will be robbing some energy from the forced air system to heat water. Since this heat came through another heat pump indoors, you're not wasting power.

01-17-19, 03:10 AM	#4
u3b3rg33k Apprentice EcoRenovator Join Date: Mar 2018 Location: Rustbelt, USA Posts: 114 Thanks: 5 Thanked 10 Times in 9 Posts	I think there's a DoE study that shows the impact of a HPWH is pretty minimal, even on homes heated by a heat pump, and that it was decisively preferable to any version of "exhausting the cold air outdoors" or running in resistance mode.

01-18-19, 01:41 PM	#5
mincus Helper EcoRenovator Join Date: Feb 2009 Location: St. Louis, MO Posts: 42 Thanks: 0 Thanked 0 Times in 0 Posts	Ok, this is what I've been doing, but always been curious as to what's best. Thanks all for the answers!