Dwellvance Methodology
How Dwellvance Calculates Heat Pump Savings
A transparent look at how the Dwellvance Heat Pump Calculator estimates heating costs, heat-pump operating costs, potential savings, installation costs, incentives, payback, and long-term economics.
What This Calculator Is Designed to Estimate
The Dwellvance Heat Pump Calculator is designed to help homeowners estimate how the economics of switching from an existing heating system to a heat pump could look under a defined set of assumptions.
The calculator brings together information about the existing heating system, energy use, local energy prices, heat-pump performance, installation cost, and applicable incentive information to estimate:
- Current annual heating cost
- Estimated heat-pump electricity consumption
- Estimated annual heat-pump operating cost
- Potential annual operating-cost savings
- Estimated installation cost
- Applicable incentives when eligibility can be verified
- Net installation cost
- Simple payback period
- Five-, 10-, 15-, and 20-year cost projections
These results are intended for planning and comparison, not as a guarantee of future energy costs or savings.
The Calculation at a Glance
Dwellvance follows a sequence of calculations rather than using a single national-average savings figure.
- Identify the existing heating system.
- Determine current heating energy use and cost.
- Convert energy use into useful heat.
- Estimate the heat-pump electricity requirement.
- Estimate heat-pump operating cost.
- Compare the two operating costs.
- Account for installation cost and incentives.
- Calculate simple payback when annual savings are positive.
Core formulas
Useful seasonal heat = energy input × existing-system efficiency
Heat-pump electricity consumption = useful seasonal heat ÷ HSPF2 ÷ 1,000
Heat-pump operating cost = electricity consumption × electricity price
Annual savings = current heating cost − heat-pump operating cost
Simple payback = net installation cost ÷ annual savings
How We Estimate the Cost of Your Current Heating System
Dwellvance first determines how much you currently spend on heating, using the information available for your home and heating system.
For fuel-burning systems, the calculation can use annual fuel consumption, the type of fuel, the applicable documented fuel price, and the existing heating-system efficiency.
Supported fuel types include natural gas, heating oil, and propane. When a verified fuel-price record is available and the energy unit matches that record, annual heating cost can be estimated from:
If a homeowner provides annual heating cost directly, that value can be used instead.
Dwellvance does not invent a fuel price when the required information is unavailable. An incomplete result is preferable to an unsupported number.
Converting Energy Use Into Useful Heat
Different heating systems use different energy units. Natural gas may be measured in therms, propane and heating oil in gallons, and electricity in kilowatt-hours.
Dwellvance converts these inputs into a common energy measure: British thermal units, or Btu.
| Energy source | Conversion |
|---|---|
| Electricity | 3,412 Btu/kWh |
| Natural gas | 100,000 Btu/therm |
| Heating oil | 138,500 Btu/gallon |
| Propane | 91,452 Btu/gallon |
For fuel-burning systems, Dwellvance then accounts for the existing system's efficiency:
Electric resistance heating is treated separately because the electricity consumed is directly converted into heat. The methodology uses 3,412 Btu per kWh while keeping electricity consumption and useful heat conceptually distinct.
How We Estimate Heat-Pump Electricity Consumption
Once useful seasonal heat has been estimated, Dwellvance estimates how much electricity a heat pump would require to provide that heating using HSPF2.
What is HSPF2?
HSPF2, or Heating Seasonal Performance Factor 2, is a seasonal measure of heat-pump heating performance. Dwellvance uses it as a seasonal performance input rather than treating the heat pump as though it operates at one constant efficiency under every outdoor condition.
Default performance assumptions
When equipment-specific HSPF2 is not provided, Dwellvance uses documented defaults based on heat-pump equipment type and climate classification.
These defaults are based on ENERGY STAR qualification criteria. They are treated as qualification thresholds, not as claims about average real-world equipment performance.
The current model distinguishes between ducted split, ductless, and single-package systems and between standard and cold-climate performance assumptions.
Dwellvance does not currently convert HSPF2 into a constant instantaneous COP or invent low-temperature performance, auxiliary-heating runtime, or backup-heating percentages when those inputs are unavailable.
How We Calculate Heat-Pump Operating Cost
Estimated electricity consumption is converted into an annual operating cost using the applicable electricity price.
Dwellvance can use documented residential electricity-rate data for the user's state when a more specific user-provided rate is not available.
A state-level residential average may differ from an individual homeowner's actual utility tariff. Where available, a user-provided electricity-rate override can provide a more specific input.
The resulting number represents the modeled heating-related electricity cost. It is not a prediction of the homeowner's complete electricity bill.
How We Calculate Potential Annual Savings
Dwellvance compares the estimated annual operating costs of the existing heating system and the heat pump.
A positive result indicates potential operating-cost savings. A negative result indicates that the heat pump is estimated to cost more to operate under the current assumptions.
Dwellvance does not force every comparison to produce positive savings. If the available assumptions indicate higher annual operating costs, that result remains visible.
This is why the result is described as potential savings rather than guaranteed savings.
How Installation Cost Enters the Calculation
Installation cost is considered separately from annual operating cost because a heat-pump project requires an upfront investment.
A homeowner-provided installation cost can be used directly. When one is not provided, the current implementation can use a documented planning-level installation-cost estimate where verified state-level data is available.
These estimates are based on published market data rather than an invented cost-per-square-foot or cost-per-ton formula.
Actual project cost can vary because of system type, required capacity, electrical work, ductwork, installation complexity, permits, contractor pricing, location, and site-specific conditions.
A Dwellvance installation-cost estimate is therefore a planning number, not a contractor quote.
How Incentives Affect the Calculation
Incentives can reduce the effective upfront cost of a heat-pump project.
Not every listed program is automatically treated as a confirmed rebate. Eligibility may depend on location, equipment, efficiency, income, ZIP or county restrictions, funding, program status, and other requirements.
A potential or unverified incentive may be shown as something worth investigating, but it does not automatically reduce the calculated installation cost or payback unless eligibility is sufficiently confirmed.
This prevents an uncertain incentive from making a project appear more affordable than the available evidence supports.
How We Calculate Simple Payback
Simple payback estimates how long it could take for operating savings to recover the net upfront cost of the upgrade.
For example, if the net installation cost is $12,000 and estimated annual savings are $2,000, the simple payback is:
$12,000 ÷ $2,000 = 6 years
If annual savings are zero or negative, Dwellvance does not manufacture a payback period. Instead, the result can indicate that there is no payback under the current assumptions.
Simple payback is a planning metric. It does not automatically account for financing, inflation, future energy-price changes, maintenance differences, equipment degradation, replacement, or discount rates.
How the 5-, 10-, 15-, and 20-Year Projections Work
Dwellvance currently provides longer-term comparisons at 5, 10, 15, and 20 years.
For each period, the model compares the estimated cost of continuing with the existing heating system against the net installation cost plus the modeled heat-pump operating costs.
Existing system cost = annual existing-system operating cost × years
Heat-pump cost = net installation cost + (annual heat-pump operating cost × years)
These projections are not forecasts of future energy prices. Unless additional assumptions are explicitly introduced, the modeled annual operating costs remain constant throughout the projection period.
The projections therefore do not silently assume electricity or fuel inflation, maintenance savings, equipment degradation, replacement costs, financing, discount rates, or future changes in heating demand.
The Assumptions Behind the Model
Dwellvance distinguishes between source-backed inputs, homeowner-provided information, documented planning assumptions, and calculated outputs.
Source-backed inputs
These can include energy conversion factors, residential energy prices, heat-pump performance criteria, installation-cost benchmarks, incentive-program information, and climate or geographic information.
User-provided information
Where possible, the homeowner's own information can take priority. Examples include annual energy use, existing-system efficiency, annual heating cost, electricity-rate overrides, installation cost, and equipment-specific performance information.
Dwellvance planning assumptions
Some parts of the model require assumptions because the information needed for a professional engineering calculation is not available from a simple homeowner calculator.
The planning heating-load model uses documented adjustments for home size, insulation, windows, air tightness, and design temperature. These are Dwellvance planning assumptions, not Manual J calculations or professional HVAC design values.
Estimated outputs
Estimated operating costs, potential savings, installation costs, net installation costs, payback, and long-term projections are outputs of the model. An estimated output should not be mistaken for a measured fact.
More decimal places do not make an estimate more accurate. Dwellvance therefore aims to identify assumptions and communicate uncertainty rather than create false precision.
What Dwellvance Does Not Claim
Dwellvance is designed to help homeowners understand the potential economics of a heat-pump upgrade. It is not intended to replace professional evaluation or site-specific engineering.
- A professional HVAC load calculation
- A Manual J heating-load calculation
- Final equipment selection or contractor sizing
- An exact prediction of future utility bills
- Guaranteed energy savings
- An exact contractor installation quote
- Guaranteed eligibility for incentives
- Equipment-specific low-temperature performance unless appropriately verified
The calculator is intended to help answer an earlier-stage question:
Should I investigate this upgrade further?
If the economics look promising, the next step may be obtaining professional load calculations, equipment recommendations, contractor quotes, and confirmation of incentive eligibility.
Why Your Actual Results May Differ
Even when the calculation is performed correctly, actual heating costs and savings can differ from the estimate.
- Energy prices can change over time.
- Existing heating-system efficiency can differ from the assumed value.
- Heat-pump performance varies with equipment and conditions.
- Actual heating demand depends on the building, weather, and operating behavior.
- Contractor installation costs can differ from planning-level market estimates.
- Incentive programs can change or impose additional eligibility requirements.
The purpose of the model is therefore not to predict the future to the dollar. It is to provide a transparent, evidence-informed starting point for comparing a potential heat-pump upgrade.
Methodology, Data Sources & Verification
Dwellvance follows a simple principle: every important real-world input should have a documented source, an explicit assumption, or be provided by the homeowner.
Depending on the calculation, documented sources can include energy conversion factors, residential electricity prices, natural gas prices, propane prices, heating-oil prices, heat-pump performance criteria, installation-cost benchmarks, incentive-program information, and climate or geographic data.
Source-backed datasets should retain relevant provenance such as source, URL, geographic scope, unit, effective date, verification date, and notes about how the data is used.
Energy prices, incentive programs, and other real-world information can change. Where a required value is unavailable or cannot be verified, Dwellvance should prefer an incomplete or qualified result over silently inventing a number.
The detailed methodology, assumptions, data sources, and climate information are maintained as separate authority resources so that the calculation approach can be reviewed independently of the calculator interface.
Use the Dwellvance Heat Pump Calculator
Understanding the methodology is useful, but the next step is applying it to your own situation.
The Dwellvance Heat Pump Calculator brings the calculation together using your home information, existing heating system, energy use, applicable energy prices, heat-pump assumptions, installation cost, and available incentive information.
A calculator can help you understand whether a heat-pump upgrade appears worth investigating. It cannot replace the next stage of professional evaluation.
The goal of Dwellvance is not to tell every homeowner that a heat pump is the right answer. The goal is to make the decision more transparent, more understandable, and better informed.