Cold-Climate vs Standard Heat Pump Lifetime Cost Calculator

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Table of contents

• How to use
• Common mistakes
• Definitions
• Methodology
• Limitations & assumptions
• Sources

Net installed cost: Installed price minus rebates and tax credits entered for that option.

All-in electricity rate: The variable electricity price per kWh, including supply and delivery charges that change with electricity use.

Auxiliary heat: Backup heat, often electric resistance heat, used when the heat pump cannot meet heating demand by itself.

Design heating load: The heat your home needs at the local cold design temperature, usually taken from a Manual J load calculation.

Capacity at 5 F: The heat a specific heat-pump system can deliver when outdoor temperature is 5 F, measured in Btu/hr.

Capacity gap at 5 F: Equipment capacity at 5 F minus the entered design heating load. A negative gap means the entered capacity is below the entered load.

COP: Coefficient of performance. It is heat delivered divided by electricity used; a higher COP means more heat per unit of electricity at that temperature.

Discount rate: A percentage used to give future costs less weight than costs paid today.

Mistake: Entering a contractor quote after rebates in Standard heat pump installed price, then also entering the rebate in Standard option rebates and tax credits.
Fix: Enter the full pre-incentive quote as the installed price and enter expected incentives only once.

Mistake: Using total household electricity in Standard option annual heating electricity.
Fix: Enter space-heating electricity only, including auxiliary heat but excluding cooling and other appliances.

Mistake: Using only the supply charge for All-in electricity rate.
Fix: Use the variable supply and delivery charges per kWh from the bill. Do not include fixed monthly charges unless they differ between options.

Mistake: Adding Standard option auxiliary-heat electricity on top of Standard option annual heating electricity.
Fix: Auxiliary electricity is already part of annual heating electricity. Enter it only to show its cost breakdown.

Mistake: Entering the unit's nameplate size as Standard option heating capacity at 5 F.
Fix: Use the published heating capacity at 5 F for the exact proposed equipment combination.

Mistake: Treating a negative Cold-climate lifetime savings value as an error.
Fix: A negative value means the standard option costs less over the selected Years to compare.

• The comparison uses user-entered quotes, energy estimates, maintenance costs, and incentives. Incorrect or incomplete inputs change the result.
• Annual heating electricity must already include auxiliary heat. The auxiliary-heat cost cards are a breakdown, not an extra lifetime charge.
• Only electricity costs grow with Yearly electricity price change. Maintenance and extra fixed service charges stay constant in nominal dollars.
• The result excludes financing, cooling costs, major repairs, replacement equipment, resale value, and costs that are identical for both options.
• A 5 F capacity gap compares one entered temperature with one entered home load. It does not replace a Manual J calculation, manufacturer performance tables across temperatures, or equipment sizing by a qualified contractor.
• Rebate and tax-credit eligibility can depend on equipment model, installation date, income, location, and tax situation.
• A positive Cold-climate lifetime savings amount is an estimate over Years to compare, not a guarantee of future utility bills or equipment life.

Cost calculation

For each option, the calculator subtracts its own entered incentives from its installed price. The default electricity rate of $0.1730 per kWh is a US planning estimate; replace it with your bill rate. [1] The 15-year default is a planning horizon, not a warranty or predicted equipment life. [2]

net installed cost = installed price - incentives

annual energy cost = annual heating electricity x electricity rate

current annual heating cost = annual energy cost + yearly maintenance + extra fixed service charges

Lifetime cost

Each year of heating electricity is allowed to change by the entered Yearly electricity price change. Each future year's energy, maintenance, and differing fixed charges are discounted using the entered Discount rate. With both rates set to 0%, the calculation is a simple cash total across the selected years.

energy PV factor = sum from t=1 to N of ((1 + g)^(t - 1) / (1 + d)^t)

recurring PV factor = sum from t=1 to N of (1 / (1 + d)^t)

lifetime cost = net installed cost + annual energy cost x energy PV factor + recurring costs x recurring PV factor

In these formulas, N is Years to compare, g is Yearly electricity price change divided by 100, and d is Discount rate divided by 100.

Comparison outputs

The savings value keeps its sign so it remains useful: positive Cold-climate lifetime savings means the cold-climate option costs less, while a negative value means the standard option costs less.

cold-climate lifetime savings = standard lifetime cost - cold-climate lifetime cost

The break-even scan starts at year 0 using net installed costs, then adds discounted yearly costs one year at a time. It reports the first whole year when cold-climate cumulative cost is no higher than standard cumulative cost.

capacity gap at 5 F = heating capacity at 5 F - design heating load

COP advantage at 5 F = cold-climate COP at 5 F - standard COP at 5 F

Worked example

With a $12,000 standard quote, a $16,000 cold-climate quote, $2,000 cold-climate incentives, 6,000 and 4,500 kWh of annual heating electricity, a $0.1730 per kWh rate, and 15 years with no growth or discounting, net installed costs are $12,000 and $14,000. With the example maintenance inputs, lifetime costs are $29,820 and $28,377.50, so Cold-climate lifetime savings is $1,442.50 and break-even occurs in year 9.