Matt Cota, executive director of the Vermont Fuel Dealers Association testified: “Cold-climate heat pumps are inadequate during the colder days in winter. Many households with heat pumps found they could not adequately heat their houses. They had to turn off the heat pumps, which are very inefficient in cold weather, and turn on their oil and propane stoves or their wood stoves.”


Since about 2010, Efficiency Vermont and VPIRG have been extolling the virtues of cold-climate heat pumps, mostly made in Japan. By end 2017, about 18000 were installed at a turnkey average cost of about $4500. Most houses need two units.


Based on an average life of 15 years, the annual cost is 2 x 4700/15 = $627/y (simple payback basis), neglecting any interest or returns on invested funds and subsidies.


- The Vermont Comprehensive Energy Plan, CEP, goal is to have 200,000 installed by 2050.

- Vermont has about 330,000 households.


Heat Pump Example in Valley News Article of March 30, 2018


An engineer had installed one cold-climate heat pump at a turnkey cost of $4655 in 2013, which underperforms during colder weather. Because it is likely the engineer had an average insulated/sealed house, he had to switch to his existing fuel oil system at about 15 F, because hiscost of operating the heat pump would have been greater than using fuel oil. The heat pump became less efficient at lower temperatures and did not deliver enough heat to his house.


Now he has two heating systems:


1) One heat pump at $4655, or 310/y (15-y simple payback), doing the light-duty work, mostly during spring and fall, plus

2) An existing fuel oil system at $10,000, doing the heavy-duty work, when it is colder than 15 F.


His average energy saving, due to electricity partially displacing oil, was $400/y (average of 2013, 2014, 2015, 2016).

The heat pump likely has maintenance, replacements and service contract costs.

He likely is barely breaking even.

All this means, only energy-efficient houses (highly insulated/highly sealed) are candidates for heat pumps.


NOTE: The coefficient of performance, COP = (Btu/h extracted from the outdoors)/(Btu/h to heat pump system, as electricity). The COP decreases as outdoor temperatures decrease. Would you like to electrically heat your house, when the COP is about 1.2 at 5 F?


Installing Heat Pumps


It would be foolish to claim to have an energy-efficient house, call an EV-approved contractor to get the subsidies, and say please install heat pumps. Some verifying and testing is required, as otherwise one may be in for a frigid surprise on cold days.


Energy-efficient houses (highly insulated/highly sealed) could be candidates for heat pumps, after successful results from:


1) Blower door test to determine existing leakage rate, ft3/h, based on existing conditions.

2) Analysis of three years of heating bills to determine the effectiveness of existing insulation and sealing.

3) Calculated heating demand reduction from sealing, additional insulation, and from replacement of windows and doors.

4) Blower door test to determine new leakage rate, ft3/h, after energy efficiency upgrades.


The Vermont Heat Pump Promotion Troika


1) GMP: Kristin Carlson, GMP's vice president for strategic and external affairs, said in an email that the utility has now installed 1,125 heat pumps.


GMP arranges for the installation with an Efficiency Vermont-approved contractor.

- The contractor chooses the heat pump brand and model; brands include Daikin, Fujitsu, and Mitsubishi, with outputs ranging from 9,000 Btu/h to 18,000 Btu/h.

- GMP loan at an interest rate is 10.74%/y. That appears to be a usury rate!

- GMP says that payments will range from $49 to $81 per month, depending on the model of heat pump that's installed.

- At $49/month, a homeowner would pay $8,820 for a single-head minisplit over the 180-month payback period.

- At $81/month, a homeowner would pay $14,580.

- That doesn't include the electricity required to run the unit.

- Should a homeowner sell the house before the loan is repaid, GMP says it can offer a buy-out price for the heat pump, or the new owner could pick up the payments.



2) Efficiency Vermont: According to a fact sheet at Efficiency Vermont, a homeowner would save:


- $1,842/y by shifting 80% of the heating load away from electric resistance heat to a cold-climate heat pump.

- Propane users would save $1,268/y.

- Fuel oil users would save $865/y.

- The “fact sheet” (fiction sheet?) is no longer accessible!


3) VPIRG, an RE Lobby: VPIRG, a booster of renewable energy, mostly financed by Vermont RE businesses, estimated the annual savings of a heat pump at $1000 to $1500 on a $3000 household heating bill. It appears, VPIRG grabbed a number out of the air, because it looked good.


People Complaining About Less than Promised Savings: The Troika made rosy savings claims that had no factual basis, but, as expected, lured people to install heat pumps. GMP and EV-approved installation contractors made a lot of money.


It is likely most heat pumps were installed in houses with average, and less than average, insulation and sealing.

It is likely people complained about less than promised savings to their legislators and to the VT-DPS.


After many complaints, VT-DPS performed a survey of actual heat pump installations and their performance.


- The DPS study found the seasonal average COP was 1.2
- The average saving was $200/y

Make sure to read the report. See URL.



Here is the main conclusion from the report:

  1. Overall dollar savings are impacted by the efficiency of the backup fossil fuel system. The higher the efficiency of the back-up system, the smaller the amount of fuel is being displaced by the heat pump.
  2. Houses with poor insulation levels and air leaks will not get as much benefit out of a heat pump, as will highly sealed, well- insulated houses.
  3. It is unlikely a heat pump by itself would be sufficient to heat a typical house, without use of a traditional heating system as a backup on cold days.


For the annual savings to be only $200/y, most of the houses had to have poor insulation and sealing. EV and its approved contractors likely did not properly survey those houses and did not give proper warning to those households. They likely were eager to install as many heat pumps as possible.


Vermont has very few energy-efficient houses (highly insulate/highly sealed), likely at most 10% of all houses. Only those houses are candidates for heat pumps. The articles in the media describing the benefits of heat pumps in glowing terms usually are regarding those houses.


There likely are another 15% of houses that could be upgraded to be energy efficient, at a cost of at least $20,000 each, which likely would make them candidates for heat pumps.


The rest of the houses (75%) are “energy hog houses” that are completely unsuitable for heat pumps, because the heat output of the heat pumps would be insufficient for those houses on cold days, say 10 F, and below. It would be too expensive to upgrade those houses for heat pumps.


It appears, the above installation targets and the estimated annual savings of the above troika are highly optimistic, i.e. fantasies based on wishful dreaming.


Highly Energy-Efficient Houses


Heat pumps work well in houses that are highly insulated/highly sealed, with south facing windows.
Such houses cool down slowly and heat up slowly.
Such houses have long time constants.
The heat pumps would operate at a near steady output, hopefully near rated output, if not oversized.
The seasonal average COP could be about 2.4 (mini-split)

EV and its approved contractors, and VPIRG have been hyping people into heat pumps; they will resort to any nonsense to fulfill the CEP goals and to make money.

However, at least 75% to 80% of houses and other buildings in Vermont are totally unsuitable for heat pumps.
That means the heat pumps are frequently cycling, which leads to low COPs.
That means back up heating systems are ON many more hours during the colder days of the winter.


About 10% of all houses in Vermont are energy-efficient houses. Air-source* heat pumps, if of sufficient capacity (they should be sized for the heating demand for worst conditions, i.e., coldest days), can extract enough heat from the cold outdoor air to heat those houses, without having to turn on propane furnaces, oil furnaces, and wood stoves.


* Ground-source heat pumps, use the soil to extract heat. The soil temperature is a near-constant 50 F throughout the year, at about 6 ft below grade, ideal for highly efficient operation of heat pumps.


- Such heat pump systems should be installed when an energy-efficient house is built.

- Such a house could have heated floors using 100 F water.

- Such a house would need a whole-house ventilation system to ensure at least 0.5 air changes per hour to each room.


Average Energy-Efficient and Energy-Hog Houses


About 90 percent of all houses in Vermont are average energy-efficient and energy-hog houses. If such houses have air-source heat pumps (turnkey cost about $4500/heat pump), their owners, likely to their surprise and dismay, have to turn on their propane furnaces, oil furnaces, and wood stoves to keep warm during colder days in winter, because air-source heat pumps cannot extract enough heat from the cold outdoor air to heat their houses.


These houses are not candidates for heat pumps, unless very significant energy efficiency upgrades are made, which usually are very costly. The uninformed and misinformed owners, who installed air-source heat pumps anyway, likely got caught into the trap of “save the world” mantras, promoted by:


1) Efficiency Vermont, a quasi-government entity, spending about $70 million per year. By means of clever PR, glossy reports, etc., EV has managed to convinced lay people, the DPS, PUC, and many legislators, heat pumps will save them money, etc.


2) VPIRG, a lobby organization and booster of renewable energy, mostly financed by Vermont RE businesses.


2) Installation contractors, approved by Efficiency Vermont. EV does not pay a subsidy to the homeowner, unless EV-approved contractors, who usually charge higher prices than normal, install the heat pumps.



Statewide Energy Code for Housing and Other Buildings 


Vermont (and NE) should have a statewide code to require zero energy or energy surplus housing and other buildings. Without such a code, there is no hope of ever reducing CO2 per CEP by 2050.



California and Duck Curves


People do not realize, California has Duck curves because housing and other buildings are so poorly insulated and sealed.


Instead of each building storing the excess electricity in batteries or in thermal hot water tanks, it is dumped into the grid. Other generators have to rapidly and inefficiently ramp down as the sun progresses.


In the evening, with solar disappearing, these generators have to rapidly and inefficiently ramp up to serve late afternoon/early evening peak demand. 


The result is chaos. California has put the brakes on installing new solar.


The fact the California Duck curve has been getting worse each year, indicates California has been doing practically nothing regarding buildings.


Energy surplus buildings, that store electrical and thermal energy, and have enough electricity left over to charge plug-ins, have to be built by the thousands in Vermont each year, to replace about 75% of buildings that basically are energy hogs.



Requirements for a 2000 sq. ft. House to be “Off-the-Grid”


The house envelope must be insulated (roof R-60, walls R-40, basement R-20, windows R-6, doors R-10) and sealed (0.6 air changes per hour, or less, during a blower door test @ 50 pascal, about Passivhaus level), to minimize energy requirements for heating, cooling and electricity. Heating and cooling would be with air-source or geothermal source heat pumps.

- One ACH for a 2000 ft^2 house is about 16000 ft^3, excluding the basement.


All this adds about 10% to the house envelope capital cost for air-source heat pumps, about 15% for geothermal source heat pumps. Land, sitework, septic, well, etc., are not part of the house envelope. 


The appliances must be high-efficiency and programmable to manage the household daily demand curve according to the weather. For example:

- The washer/dryer would be operated during sunny periods, not during cloudy/rainy/snowy periods

- LED lights would go on/off upon entering/leaving a room.

- Here is a daily demand curve for a typical household.



The house should be oriented to solar south and have:


- A roof-mounted solar system, 10 kW; production in Vermont, 12,500 kWh/y; turnkey capital cost $35,000

- 2 Tesla Powerwall 2.0 battery units; AC to AC round-trip efficiency 90%; input 14.74 AC, stored 14 kWh DC, output 13.3 kWh AC; turnkey capital cost $16000.


- A propane-fired generator, 3 - 5 kW, to top off batteries, as needed, mostly during winter; turnkey capital cost $1000.

- A well-insulated domestic, domestic hot water storage tank, 300-gallon, with 1) electric resistance heater and 2) propane-fired heater in the basement.

- Centrally located heat pump with air supply/return ducts for each room, 0.5 ACH.


In heating mode, the heat pump receives a mixture of 50% recirculated air and 50% pre-heated, filtered, fresh air and delivers warm air as needed. The preheating allows the heat pump to operate at a higher COP.


In cooling mode, the heat pump receives a mixture of 50% recirculated air and 50% pre-cooled, filtered, fresh air and delivers cool air as needed.  


- Air-to-air heat recovery unit, efficiency 85%, to preheat incoming fresh air and ventilate stale air to the outdoors, located in air supply duct, upstream of heat pump.

- HEPA filter to reduce pollen, bacteria and spores, located in air supply duct, likely upstream of heat recovery unit.

- A backup, thermostatically controlled electric heater, about 2 kW, for space heating, located in air supply duct, downstream of heat pump, in case of heat pump failure.


Excess electricity could be used to heat an outdoor Jacuzzi, Sauna, or to top off the charge of a plug-in hybrid or EV, during the Spring, Summer and Fall.


NOTE: Typical NE houses, 10 to 20 years old, have leakage rates of 3 - 5 ACH @ 50 pascal, and would be totally unsuitable for space heating with heat pumps. Yet, installation contractors, approved by Efficiency Vermont, and eager to make a buck, persuade homeowners to install heat pumps anyway. Homeowners have no idea they likely will have inadequately heated houses during colder winter days.




 The actual stored energy in the Powerwall 2.0 is 14/0.70 = 20 kWh DC, because the unit is maximally charged up to 95% and minimally discharged down to 25%, i.e., 20/0.95 = 21.05 kWh AC enters the battery.

The delivered 14 x 0.95 = 13.3 kWh AC depletes the battery by 14 kWh DC.

The remaining charge, 20 - 14 = 6 kWh DC, stays in the battery.



Converting from US to SI units

R = 1/U = delta t/heat flux = delta t/(energy rate/unit area)

R (US units) = F/{(Btu/h)/ft^2} = (F.ft^2)/(Btu/h) = (5/9 x 0.092903)/(1055.0556/3600) = 0.17611 K.m^2/W

RSI (SI units) = K/{(joule/s)/m^2} = K. m^2/(joule/s) = 1 K.m^2/W

RSI = 5.67826 x R


F = 5/9 K

ft^2 = 0.092903 m^2

Btu = 1055.0556 joule

W = J/s




Energy-Surplus Buildings and Plug-in Vehicles: Turning around the US building stock to energy-surplus buildings, and the vehicle stock towards plug-ins would take some decades.



Ideally, all residential and other buildings should be energy-surplus buildings:


1) Highly insulated and sealed.

2) Energy efficient systems and lighting.

3) Heat pumps for space heating and cooling and hot water.

4) Battery systems; store PV solar during midday, use in the evening

5) Thermal storage systems; store PV solar, use as needed

6) PV solar systems. 


Such buildings would:


1) Take a long time to warm up or cool down, i.e., the internal temperature would vary just a few degrees during a day, even though the outside temperature would vary 30 degrees or more.

2) Use minimal energy for heating, cooling and electricity (Btu/ft2/y)

3) Have enough electricity left over to charge plug-in vehicles at night.


Such a setup would greatly reduce the daily variation in electrical demand, and thus reduce the need for generating capacity, MW.


However, almost all of the building stock is very far from highly insulated/highly sealed, etc.: they are energy-hog buildings. Placing solar panels on the roofs of such buildings makes for good visuals, but creates grid disturbing duck curves, especially in California.



Heat Pump Performance: The heat pump COP on MFR data sheets is for test operation at a source temperature of 47F.

That temperature is per industry standard.

Heat pumps from Japan are well-designed, reliable, high tech systems.

They work well in houses that are highly insulated and sealed, such as with R-6 to R-9 triple glazing, R-5 to R-10 insulated doors, R-40 walls, R-20 basement, R-60 roof, 85% efficient heat recovery ventilator, open floor plan, preferably all on one floor.

The glowing media reports about heat pumps, often written by lay reporters, usually involve such houses.

Such houses have long time constants; slow to warm up, slow to cool down.

You may want to look up the PassivHaus standard, which has been around for  at least 30 years.


The COP of a heat pump decreases when the source temperature decreases, say to 0 F.

This happens on colder days in winter when heating requirements are higher.

Owners find they cannot heat their houses, so they turn on their traditional furnace, or wood stove.

That means their heat pumps operate mostly during moderately cool days.

Under those conditions the opportunities for annual savings are minimal.


Overhyping Heat Pumps: Efficiency Vermont, VPIRG, etc., have been shamelessly overhyping heat pumps. 

VPIRG, a lobby organization, booster of renewable energy, mostly financed by Vermont RE businesses, estimated the annual savings at $1000 to $1500 per year on a $3000 household-heating bill.   

EV provides subsidies, and EV-qualified contractors charge a little more because of the subsidies.


People Complaining About Less than Promised Savings: It is likely many heat pumps were installed in houses with average insulation and sealing. It is likely people complained to their legislators, etc., about less than promised savings. As a result the VT-DPS made a survey and wrote a report, and found average annual savings were $200/y (for a $4500 installation that will last about 15 years, not counting any costs for service plans and maintenance.


From the VT-DPS report:


  1. Overall dollar savings are impacted by the efficiency of the backup fossil fuel system. The higher the efficiency of the back-up system, the smaller the amount of fuel is being displaced by the heat pump. 
  2. Houses with poor insulation levels and air leaks will not get as much benefit out of a heat pump, as will highly sealed, well- insulated houses. 
  3. It is unlikely a heat pump by itself would be sufficient to heat a typical house, without use of a traditional heating system as a backup on cold days. 



NOTE: For the annual savings to average only $200/y, most of the houses had to have poor insulation and sealing. EV and its approved contractors likely did not properly survey those houses and did not give proper warning to those households. They likely were eager to install as many heat pumps as possible.



The ratedCOP of a heat pump is the energy out/energy input at a source temperature of 47 F.

The rated COP is determined under test conditions in a laboratory


The average COP is less at lower than rated outputs, and due to on/off cycling, and as source temperature decreases, i.e., the heat pump output decreases as it get colder. That perversity happens when the heating load of a building is increasing!


In the real world, the heating load of a building increases exponentially as it gets colder, i.e., it is not linearly increasing, but with an exponent greater than 1, say 1.2


Owners know their heat pumps are working hard, because fans are at high speed, it is cold outside, say 0 F, the COP decreases to 1.2 to 1.4, but they do not get enough heat their buildings.


Owners may run under such conditions more hours than they should.

Efficiency Maine recommends owners to “set it and forget it”. That surely is the most stupid notion of the year.

A better approach is to turn off the heat pump and use only the traditional furnace, or wood stove on colder days

All that leads to little savings.


Houses Built to the Passivhaus Standard

Such houses, with the heating system off, take at least a day to cool down 1 to 2 degree F on cold days in winter, because of internal heat generation by people, lighting and appliances, food heating, solar gain. 

A 2000 sq ft house would require only a resistance heater of about a 1.5 to 2.0 kW to maintain temperature and heat domestic hot water.


NOTE: A standard fuel oil furnace may be rated at 85% efficiency, but the seasonal average efficiency likely would be about 70%, because of the system loosing heat up the chimney after it shuts down, and due to having to warm up again after it starts up, just as with a car.









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