Ductless Heat PumpsDuctless Heat PumpsDetermining Cost SavingsDetermining Cost Savings

ExampleExample

Gary NordeenGary NordeenBill Kingrey, P.E.Bill Kingrey, P.E.

11/5/08 AFE Webinar11/5/08 AFE Webinar

IntroductionIntroduction

This presentation will help you to determine potential cost savings using ductless heat pumps

Step 1: Determine Fuel CostsStep 1: Determine Fuel Costs

Real Fuel Costs Include:• Taxes• Demand charges for electricity• Meter charge, minimum payments• Fuel consumption charges

Calculate Fuel CostsCalculate Fuel Costs

•Divide total bill for each fuel type by # of units of fuel

•Use a winter month bill for heating supplement and a summer month bill for cooling supplement

Electricity = total bill / #kWh used

Gas = total bill / # therms used

Oil = total bill / # gallons used

Step 2: Estimate Existing Step 2: Estimate Existing System EfficiencySystem Efficiency

• Cooling Mode: divide seasonal energy efficiency ratio (SEER) of chosen heat pump by 3.413

SEER / 3.413 = Efficiency in cooling mode

• Heating Mode: divide heating seasonal performance factor (HSPF) by 3.413

HSPF / 3.413 = Efficiency in heating mode

Step 3: Calculate Cost of Step 3: Calculate Cost of EnergyEnergy

Use the following table

OR

the Fuel Cost Calculators at www.nwBuildings.org/dhp.aspx

Fuel Cost TableFuel Cost TableCost Approx.

FUEL Units Factor Efficiency#2 Fuel Oil $/gal .1396 .82#6 Bunker $/gal .1524 .82Coal $/ton 23 .77Cord Wood $/Cord 18 .60Electricity $/kWh .003417 1.00Heat Pump $/kWh .003417 2.50Natural Gas $/therm .1 .80Propane $/gal .0915 .80Wood Pellets $/ton 16 .77

Cost / mmBTU = Fuel cost / (Cost Factor x Efficiency)

Alternative: Use handy spreadsheet at: www.nwbuildings.org/dhp.aspx

Sample Calculations FollowSample Calculations Follow

The sample uses Fuel oil and Electricity prices to calculate the delivered cost of heating and cooling in a large building, then compares it with the cost of supplying heating and cooling with a ductless heat pump.

Step 1: Calculating Fuel CostsStep 1: Calculating Fuel Costs

Fuel Oil#2 Fuel oil @ $3.00/gal burned at 82%

efficiency =$3.00 / (.1396 x .82) = $26.21 / mmBTU

ElectricityElectricity @ $.112 / kWh at 100%

efficiency =.112 / (.003417 x 1.0)=$32.78 / mmBTU

Step 2: Estimate Large Cooling Step 2: Estimate Large Cooling System EfficiencySystem Efficiency

• To calculate savings in a system to supplement cooling you need to know the efficiency of the existing system

• Estimate the EER (8 to 18) of the chiller system – including cooling tower and pumps and divide by .03413 to obtain the efficiency

• Or use efficiency of 250% for air–cooled units, 250 to 330% for water cooled units

Gather the InformationGather the Information

• Assume the building is newer and the water-cooled chiller runs at 300% efficiency

• Assume the “real” cost of electricity is

$ 0.12 / kWh

• Cooling costs = $11.71 / mmBTU

Determine Energy Costs for Determine Energy Costs for Ductless Heat PumpDuctless Heat Pump

• SEER = 19 • COP = 19 / 3.413 = 5.57 = • 557% Efficiency• Fuel Cost is $ 6.30 / mmBTU

• Fuel Cost Savings is

$ 11.71 - $ 6.30 = 5.41 / mmBTU

What Did We Learn?What Did We Learn?

• The existing HVAC system is providing cooling at about twice the cost of the DHP

• We can justify the DHP on cost savings for cooling-only

• Can we justify the DHP on heating performance or improved comfort?• Repeat the analysis using the heat pump

efficiency of HSPF/3.413 and the appropriate fuel cost and efficiency for the building heating system.

More InformationMore Information

Northwest Building Efficiency Center

www.nwBuildings.org/

Info@nwBuildings.org

866-929-6232