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This commentary is by Robert Wood of Holland, Vermont.
Jonathan Baker's recent complaints about heat pumps are not unique.
As a result of a few years of multiple complaints by various heat pump users, mainly about energy cost savings being much less than stated on the renewable energy websites of Efficiency Vermont, GMP, VPIRG, etc., VT-DPS was ordered by the Vermont Legislature to hire a consultant to perform a survey of actual heat pump installations and their performance.
CADMUS, the consultant, gathered the operating data of 77 heat pumps at 65 sites, to determine annual energy cost savings of the heat pumps.
The study lasted from November 2015 through the spring of 2017. The CADMUS study found:
The annual energy cost savings were, on average, $200 per year, but the annual maintenance and annual amortizing costs (at 3.5% per year for 15 years) would turn that gain into a loss of at least $200 per year.
This does not include the substantial increase in monthly electricity bills (I'm currrently paying 18.5 cents per kilowatt-hous), the cost of annual maintenance contract fees (at about $150 per year, no parts), cost for incidental repairs and unscheduled outages (at about $150 per call, no parts), annual loan payments to utilities, or amortizing the $5,000 heat pump at about 3.5% for 15 years and amortizing the $10,000 traditional back-up system at about 3.5% for 20 years.
The energy cost savings noted above of about $200 per year per year was in stark contrast to the $1,200 to $1,800 per year touted by the renewable energy advocates and Efficiency Vermont, GMP, VPIRG, VT-DPS, VEIC, etc. After release of the CADMUS report, those estimates disappeared from the websites.
On average, the heat pumps provided 27.6% of the annual space heat, and traditional fuels provided 72.4%, numbers directly from the CADMUS survey data. The small percentage of displaced fossil fuel heat indicates heat pumps would not be effective CO2 reducers in the cold climate of Vermont, if used in average Vermont houses.
Average Vermont houses are poorly insulated, do not have open floor plans, and comprise about 90% of the Vermont housing stock.
- Owners started to turn off their heat pumps at about 28F to 30F, because their experience showed significant increases in electricity bills, if they had not turned them off.
- Very few owners were using their heat pumps at 10F and below, as shown by the decreasing kWh consumption totals on figure 14 of URL. Effiency dropped off markedly while cost rose markedly.
- At those temperatures, the hourly cost of operating heat pumps exceeded the hourly cost of using a traditional heating system.
- This statement is true for average Vermont houses, about 90% of the Vermont housing stock.
Apparently the Legislature never read (or buried) the study it mandated.
Consumer Reports found that, "based on our analysis, we determined that, on average, around half of heat pumps are likely to experience a break by the end of the eighth year of ownership, which is about the midpoint of the expected life of the system. Our members said they expect their heat pumps to last a median of 15 years."
The Burlington Electric Department In 2018 scaled back incentives for cold climate heat pumps. According to the department, Efficiency Vermont's estimated savings were grossly exaggerated: "BED is scaling back its 2018-2020 projections of ccHPs installed in the City due to the results of a 2017 DPS evaluation report. That evaluation indicates that the forecasted ccHP-related savings based on Efficiency Vermont’s analyses were roughly twice the actual savings that customers participating in the evaluation study experienced.
Brookhaven National Laboratory developed an 8,760-hour model of a 2,500-square-foot Maine home. The study concluded that, while a cold-climate heat pump is more efficient than oil heat at and above 48 degrees, oil heat is more efficient than a cold-climate heat pump when temperatures dip below 48 degrees Fahrenheit.
I am unaware of newer studies or miraculous improvements over the past five years in technology, efficiency or costs of cold-climate heat pumps that would negate these findings.
Thanks to Wilhelm Post for contributing many of the references.