Ductless Heat PumpsMyths, Modeling and Mesmerizing Material

Myth:

Ductless Heat Pumps don’t work when it is cold out.

Heating System Performance versus Outdoor Temperature

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DHP & Oil Boilerefficiency vs. temperature

High Efficiency Cold Climate DHP COPBoiler COP

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DHP & Oil Boilercapacity vs. Temperature

High Efficiency Cold Climate DHP Capacity Boiler Capacity Stnd DHP Capacity

Metered COP: VT Evaluation

Myth:

Ductless heat pumps cost more than your oil system to run when its cold out.

Heating System Costs v Outdoor Temperature

Assumptions:

$0.16/kWh

$2.75/gallon of oil

The cost of each unit of heat (btu) produced by a DHP varies as a function of outdoor temperature.

High efficiency ductless heat pumps cost less to operate than standard efficiency ductless heat pumps.

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Outdoor Temperature (Tout)

DHP & Oil Boilercost vs. temperature

Oil $/MMBtu High Efficiency Cold Climate DHP Stnd DHP $/MMBtu

Temperature Time Series (hourly data)

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Portland TMY3 Dry-bulb (F) Caribou TMY3 Dry-bulb (F) Bangor TMY3 Dry-bulb (F)

“Binning” of Temperature for Analysis

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Portland Bangor Caribou

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TMY and Modeled Heating hours

Caribou Caribou Gated heating

Modeled Results: Heat Supplied – High Efficiency Cold Climate DHP vs. Oil Boiler

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capacity ASHP can deliver kBtu/h ASHP actual delivered kBtu/h

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Heat Supplied

DHP heat supplied Boiler heat supplied

Modeled Results: Cost of Heating – High Efficiency Cold Climate DHP vs. Oil Boiler

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DHP & Oil Boilercost vs. temperature

Oil $/MMBtu High Efficiency Cold Climate DHP Stnd DHP $/MMBtu

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Cost of Heat Supplied

High Efficiency Cold Climate DHP Oil 'Make-Up' Only Central System

Modeled Results: Cost of Heating – High Efficiency Cold Climate DHP vs. Standard Efficiency DHP

Base-only annual operating cost $1,189

EE DHP + base annual operating cost $879

$ saved estimated $310

ASHP annual operating cost $650

Base-only annual operating cost $1,189

EE DHP + base annual operating cost $996

$ saved estimated $193

ASHP annual operating cost $271

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Cost of Heat Supplied

High Efficiency Cold Climate DHP Oil 'Make-Up' Only Central System

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Cost of Heat Supplied

Standard Efficiency DHP Blended Fuel "Make-Up' Only Central System

Modeled Results: “Cutover”

"lost" savings from not cutting off DHP $ 1.22

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Cost of Heat Supplied

DHP Cost Oil 'Make-Up' Boiler Cost without DHP

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Cost of Heat Supplied

DHP Cost Oil 'Make-Up' Boiler Cost without DHP

Heat Pump User Tips

Myth:

You should turn down the temperature setting on your ductless heat pump at night and when you’re not home.

• Comparison of two identical houses using DHP’s as primary heat sourceso One home sets the thermostat based on comfort and occupancy

o One home sets the thermostat

• Long term Monitoring

• Short Term Comparison

National Renewable Energy Laboratory Case Study

Constant Set Point

From: https://www.nrel.gov/docs/fy15osti/63080.pdf

On Off Operation

https://www.nrel.gov/docs/fy15osti/63080.pdf

Setback and Constant Operation

https://www.nrel.gov/docs/fy15osti/63080.pdf

Heat Pump User Tips

Myth:

Ductless Heat Pumps will be used for air conditioning and break the grid in the summer.

DHP Reduce Air Conditioning’s Impact on Peak Load

• Vermont published the evaluation of DHP’s in November, 2017

• The evaluation found that on average DHP’s reduce cooling load:

• The Vermont evaluation examine the AMI data before and after a DHP was installed. o Table reflects net savings:

Cooling (cont)

Evaluations

• Massachusetts published the evaluation of DHP’s in December, 2016

• Vermont published the evaluation of DHP’s in November, 2017o Both studies found that the units were not being used as much as anticipated

• Vermont may be most comparable to Maine

Evaluation Results from Vermont and Massachusetts

Vermont DHP Usage

Integrated Thermostats

• 7 Homes with Mitsubishi DHP previously metered• Honeywell Thermostat (VisionPRO 8000) integrated with DHP (through

interface kit box PAC-US444CN-1) and Existing Central Heating System zone shared with DHP

• Remotely mounted wireless temperature sensor configured to control DHP and central system

• Droop between DHP and central system set to 2-3 deg F• Before Thermostat Integration

o 317 gallons of Oil offset with DHP

• After Thermostat Integrationo 607 gallons of Oil offset with DHP

Integrated Thermostat

Lessons Learned

• DHP’s can deliver significant benefits to customers

• The more they are used the higher the benefits

• DHP’s operate differently that conventional systems

• Customer education and orientation is needed

Lessons Learned