Heat Pump Water Heaters

Slickcraft · 02-01-2014, 02:27 PM

The NH Electric Co-op has an incentive program for installation of new units:

http://www.nhec.com/filerepository/j...2014_final.pdf

Quote:

Incentives Up
to $600 on Heat
Pump Water
Heaters
Most homeowners who have heat pumps
use them to cool and heat their homes.
But heat pumps can also be used to heat
water, and your New Hampshire Electric
Cooperative (NHEC) is offering incentives
up to $600 to install qualified systems.
How They Work
Heat pump water heaters use electricity
to move heat from one place to another
instead of generating heat directly. This
means they can be two to three ti mes
more energy efficient than conventional
electric resistance water heaters. To move
the heat, heat pumps work like a refrig-
erator in reverse. While a refrigerator
pulls heat from inside a box and dumps it
in to the surrounding room, a stand-alone
air source heat pump water heater pulls
heat from the surrounding air and dumps
it – at a higher temperature – into a tank
to heat water.
Pay a Little More Now, Save a Lot Later
While a qualified heat pump water heater
costs more upfront, it can save the aver-
age household nearly $300 per year on its
electric bills compared to a standard elec-
tric water heater. NHEC will help shorten
your payback time by offering a $500
incentive for the installation of a 50-gallon
heat pump water heater and $600 for an
80-gallon heat pump water heater. There
are certain program requirements so
please visit the program page on our web-
site: www.nhec.coop/energysolutions

DickR · 02-01-2014, 07:03 PM

Heat pump water heaters (HPWH) perform most favorably in warm climates, where the norm is use of AC to remove heat from the house. Bear in mind that a HPWH pulls heat from the air surrounding the heater and moves it to the water inside the tank. There must be adequate air volume around the unit to provide the heat moved into the tank. That air volume will be cooled, as heat is withdrawn from it. That heat must be replaced.

In summer, in a house into which normally a fair amount of outside heat leaks and might otherwise have to be removed via air conditioning, a HPWH might be a good way of relocating that heat to water that must be heated anyway. Some dehumidification is obtained in the process (and thus there is the need for condensate draining/removal). I doubt that the summertime average efficiency would give more than twice the heat into water than otherwise provided by the electric power used by the HPWH. A COP of 3.0 is overly optimistic for this application.

In winter, the heat removed from the air around the HPWH must be replaced by whatever heating system is used to heat the house. If that heat source is cheaper, per BTU of heat provided, than straight electric resistance heating, then a HPWH will provide hot water at less expense, although the economics of running the HPWH in winter won't be anywhere near what it can be in summer. There is of course the comfort issue of the air in the space around the HPWH being cooled substantially, at a time when the house is being heated.

Overall, averaged through the year, more heat is delivered to water via a HPWH than via straight electric resistance heating, but offsetting this is the added cost of the HPWH equipment, which ultimately must be serviced or replaced after so many years of operation. The NHEC incentives help in this regard, but I have to wonder about the overall economics of adding the complication in a heating climate such as ours (climate zone 6).

There has been considerable discussion of HPWH on well-regarded sites such as www.greenbuildingadvisor.com. A search there brings up quite a number of discussions about HPWH.

KDL · 02-02-2014, 07:07 PM

I have a heat pump water heater and am very pleased with its performance. They do pull heat from the surrounding area but the cooling of that area is not noticeable. Energy usage is approximately 1/3 of a standard electric tank. Well worth the investment.

02-01-2014, 07:03 PM	#2
DickR Senior Member Join Date: Apr 2008 Location: Moultonborough Posts: 735 Thanks: 4 Thanked 254 Times in 166 Posts	Heat pump water heaters (HPWH) perform most favorably in warm climates, where the norm is use of AC to remove heat from the house. Bear in mind that a HPWH pulls heat from the air surrounding the heater and moves it to the water inside the tank. There must be adequate air volume around the unit to provide the heat moved into the tank. That air volume will be cooled, as heat is withdrawn from it. That heat must be replaced. In summer, in a house into which normally a fair amount of outside heat leaks and might otherwise have to be removed via air conditioning, a HPWH might be a good way of relocating that heat to water that must be heated anyway. Some dehumidification is obtained in the process (and thus there is the need for condensate draining/removal). I doubt that the summertime average efficiency would give more than twice the heat into water than otherwise provided by the electric power used by the HPWH. A COP of 3.0 is overly optimistic for this application. In winter, the heat removed from the air around the HPWH must be replaced by whatever heating system is used to heat the house. If that heat source is cheaper, per BTU of heat provided, than straight electric resistance heating, then a HPWH will provide hot water at less expense, although the economics of running the HPWH in winter won't be anywhere near what it can be in summer. There is of course the comfort issue of the air in the space around the HPWH being cooled substantially, at a time when the house is being heated. Overall, averaged through the year, more heat is delivered to water via a HPWH than via straight electric resistance heating, but offsetting this is the added cost of the HPWH equipment, which ultimately must be serviced or replaced after so many years of operation. The NHEC incentives help in this regard, but I have to wonder about the overall economics of adding the complication in a heating climate such as ours (climate zone 6). There has been considerable discussion of HPWH on well-regarded sites such as www.greenbuildingadvisor.com. A search there brings up quite a number of discussions about HPWH.

02-02-2014, 07:07 PM	#3
KDL Senior Member Join Date: Jun 2009 Posts: 118 Thanks: 0 Thanked 14 Times in 11 Posts	I have a heat pump water heater and am very pleased with its performance. They do pull heat from the surrounding area but the cooling of that area is not noticeable. Energy usage is approximately 1/3 of a standard electric tank. Well worth the investment.