The economic balance point describes the outdoor air temperature at which operation of the heat pump’s backup heating system would cost the same to run. This will vary greatly based on the fossil fuel type, cost, and the efficiency of the equipment. Typical economic balance points for a natural gas furnace as back up is between 40-50°F while a propane furnace would have an economic balance point closer to 15-20°F. When conducting annual maintenance on your heat pump, talk to your contractor to determine if the switchover point should be changed. To illustrate these balance points according to fuel prices, the Minnesota Air Source Heat Pump Collaborative developed the chart shown in Figure 10. Using A Programmable Thermostat $0.11
Figure 10. Switchover temperature guide for dual-fuel developed for the MN Air Source Heat Pump Collaborative.
ECONOMIC BALANCE POINT FOR DUAL FUEL
The chart below shows how to select the economic switchover temperature of a dual fuel ASHP installation Note: this assumes cold climate product is sized to meet the heating load of the home.
Natural gas rate, $/therm, (furnaces and boilers)
$0.60 $0.65 $0.70 $0.75 $0.80 $0.85 $0.90 $1.00
$1.15
$1.33
$1.50 $2.00 $2.50 $2.75
$0.05
25°
20°
15°
10°
5°
0°
-5°
-10°
-10°
-10°
-10°
-10°
-10°
-10°
$0.06
35°
30°
25°
20°
15°
15°
10°
0°
-10°
-10°
-10°
-10°
-10°
-10°
$0.07
45°
40°
35°
30°
25°
25°
20°
10°
0°
-10°
-10°
-10°
-10°
-10°
$0.08
50°
45°
40°
40°
35°
30°
25°
20°
10°
0°
-10°
-10°
-10°
-10°
$0.09
60°
55°
50°
45°
40°
40°
35°
30°
20°
10°
0°
-10°
-10°
-10°
$0.10
60°
60°
55°
50°
50°
45°
40°
35°
25°
15°
10°
-10°
-10°
-10°
60°
60°
60°
60°
55°
50°
45°
40°
30°
25°
15°
-5°
-10°
-10°
$0.12
60°
60°
60°
60°
60°
55°
50°
45°
35°
30°
20°
0°
-10°
-10°
$0.13
60°
60°
60°
60°
60°
60°
55°
50°
40°
35°
25°
5°
-10°
-10°
$0.14
60°
60°
60°
60°
60°
60°
60°
55°
45°
35°
30°
10°
-5°
-10°
$0.15
60°
60°
60°
60°
60°
60°
60°
60°
50°
40°
35°
15°
0°
-5°
$0.16
60°
60°
60°
60°
60°
60°
60°
60°
55°
45°
40°
20°
5°
0°
$1.22 $1.83 $2.29 $2.52 Propane rate, $/gallon, (furnaces and boilers) $1.37
A programmable thermostat can be used with a heat pump. However, large setbacks like the ones that are preprogrammed when you purchased it are not suggested. It’s best to create a custom schedule based on when you wake up, leave your house, and go to bed. Only decrease the indoor temperature by three or four degrees during these events in the winter. This is most important for homes using all electric heat pumps, but homes with propane and oil can also see significant savings. Make sure you check with your contractor to ensure your thermostat will work with the heat pump. Using A Smart Thermostat
Similar to a programmable thermostat, a smart thermostat can be used with most heat pumps. They can also be a better option for seasonal cabins with an internet connection or where you want easy access to the thermostat without going to another part of the house. When using a smart thermostat with a heat pump, verify it is not automatically using a preprogrammed setback or auto away mode to avoid large temperature setbacks. When leaving for extended periods of time, such as for the winter, be sure the temperature is reduced as much as possible but never below 55°F in the heating season. When getting ready to return, just open the smart thermostat app and turn the heat up to your preferred temperature. By the time you arrive, your home should be nice and comfortable. Only set your thermostat back three or four degrees at night or when leaving the house. Since a heat pump’s output capacity is lower than a traditional furnace, it will run longer than your furnace does. This helps keep temperatures in your home more comfortable. Coordinating Your Heating If You Also Have A Separate Boiler, Resistance Heat, Or Backup Heating System When your new heat pump provides heating and cooling for your main living area, set the existing thermostats to your old heating system back five or six degrees. Then set the new heat pump to your preferred comfort temperature. If the heat pump can’t maintain its set temperature, the boiler or backup heating system will turn on.
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ELECTRIC HEAT PUMP CUSTOMER BUYING AND OPERATION GUIDE FOR SINGLE-FAMILY HOMES
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