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Wednesday, January 11, 2017

Home Energy Use 1

Heat Pumps for Residential Use

For the US as a whole, electricity is responsible for 43% of residential GHG emissions.  Natural gas for space heating and hot water heating is responsible for 46% of residential GHG emissions nationwide.  The remaining 11% is home heating oil, wood, & kerosene.  In California, where heating oil is seldom used, space heating and hot water heating are mostly gas comprising 52% of home energy use (click on chart to enlarge).

Space Heating + Water Heating = 52% of CA Home Energy Use
This represents about one third (33%) of annual home energy costs as seen in the next chart (click to enlarge):
It is fairly easy to eliminate the use of natural gas for these applications with electrically powered heat pumps, hot water heat pumps, and/or "tankless" hot water heaters.  If the source of the electricity is clean energy (like solar panels) then you have eliminated over 50% of residential GHGs.

"Comparative Energy Use of Residential Gas Furnaces and Electric Heat Pumps"

Below is a hybrid heat pump hot water heater in the Lowe's catalog.  The "hybrid" refers to the fact that when the outside air is really cold (below 40) an electric heating element will kick in.  Otherwise it uses the much more efficient electric heat pump.

The advantage of heat pumps is not only GHG reduction and the elimination of natural gas, (and of 'fracking') but a considerable cost savings as well as seen in the following chart (click chart to enlarge):
The annual heating costs of a Geothermal Heat Pump are only 32% that of a common natural gas furnace and even less costly than most other forms of heating.

How They Work

Heat pumps are present in most homes.  They are called refrigerators and air conditioners!  What they are doing is pumping the heat from the inside of an enclosure - refrigerator or room - to the outside.  Typically there is a little vent in the bottom or rear of a refrigerator that blows warm air out.  A room air conditioner also has to have a heat exhaust to the outside as it moves the heat from the inside.

"Heat pump water heaters use electricity to move heat from one place to another instead of generating heat directly. Therefore, they can be two to three times more energy efficient than conventional electric resistance water heaters. To move the heat, heat pumps work like a refrigerator in reverse."

Here is a diagram of a hot water heat pump (click to enlarge):
Heat pumps work differently in different climates as the following map shows :
Same Stiebel link as above
More resources:

How it works even in Vermont:

State of VT on heat pump hot water heaters (click to enlarge):
Nice infographic from US Government:

More explanation:

InfoGraphics for 16 selected states on energy use

Tankless vs Heat Pump hot water heaters.