HVAC Update with Heat Pump

Now that more of our home electricity requirements are provided by solar energy, it was time to upgrade our HVAC system to a heat pump, instead of just replacing the old central air conditioning unit. A far more efficient gas furnace was also installed for heat backup, when temperatures drop below freezing.
Solar panels with snow removed
Here are the latest statistics and comparisons related to the July 2021 dual fuel (electric/gas) upgrade on our home’s HVAC system. We installed a SEER 15 heat pump (it heats and cools) and a 96% efficient gas furnace, for backup heat during below freezing temperatures. Previously, we had an 85% efficient gas furnace (35 years old) and a central AC unit that was on the low end of today’s efficiency standards, plus it used a recently discontinued refrigerant.

GOAL: Use less energy, primarily less gas.

March 2021 usage of 94 Therms
March 2022 usage of 41 Therms

We used 56% less natural gas year-over-year:
41 Therms this year vs 94 Therms last year

13 month gas usage history
13 month electricity usage history
The above chart from our electric company clearly illustrates two things:
  1. More energy from our solar panels went directly into home usage instead of back onto the electric grid for ‘net metering.’
  2. More electricity was delivered to our house from the grid.  Note: Some was in the form of ‘banked credits’ being returned to us from ‘net metering.’

487 kWh (March 2022) minus 226 kWh (March 2021) =
261 kWh more (115% increase) in electricity usage

Our combined cost for gas and electric in February-March was 18% lower year-over-year. Note: Electric bill of $30.37 included over 600-miles of EV car charging.
Energy efficiency report for Chevy Bolt

Using electricity instead of gasoline saved at least $95 for the one month period, and that doesn’t even take into consideration the “free” portion of the electricity from our solar panels.

  • The SEER 15 rated heat pump we purchased is on the low end of the heat pump efficiency scale, with considerable price increases for better heat pumps up to, and beyond, SEER 20. There are energy tax credits available. More information
  • In a new home situation, or even a location with a larger yard, we would have installed a ground-sourced heat pump (where coils run deep into the ground, taking advantage of steadier soil temperatures for both heating and cooling) instead of our air-sourced heat pump, that deals with much wider ranging air temperature fluctuations. Think: Geothermal called “Geoexchange.”
  • I still find it amazing that a heat pump can create heat from frigid air in the 30’s. 
    Some heat pumps can do that from much colder temperatures!
  • The heat (from our heat pump at least) feels “luke warm” when compared to heat sourced from our backup gas furnace.
  • Cooling is much improved over our old central AC unit, and far more energy efficient.  Below: Diagram of a “Geoexchange” system. More information
Geoexchange system

One Comment on “HVAC Update with Heat Pump

  1. Hi Bob–We built our home in 2007 and we have geothermal heating and cooling. The upfront charge was higher choosing that system, but we were told we would “break even” after about 7 years, and we knew we would be here a long time. Come 2022, it’s a good system except for the ongoing problems with the Water Furnace itself. There have been multiple breakdowns over the years and we’ve had to spend thousands of dollars for replacement parts, including the motherboard, the fan motor, and the evaporator coil (more than $3,000 just for that). If the condenser goes then we will really be in trouble. The refrigerant replacement for the evaporator coil was also very expensive. We also priced getting a new Water Furnace and it seems the prices have really shot up in the past year or two. –Julie DiCenzo

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