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Estimate your savings

See what a window-film kit could save your home in a heating season. Nothing you enter is stored unless you choose to save it.

Five digits. SaveWave covers US homes for now, and your ZIP code tells it how cold your winters are.

Enter what you pay per unit.

One setting for all your windows: pick the one that fits most of them.

Your windows

Add a row for each window size. Measure the glass in inches.

1 window, about 11 square feet of glass.

Your estimate

Estimate

Enter your ZIP code to see an estimate.

Save it to your page: once your kit is up, choose a share and see how soon it could fund a $25 gift. Next, sign up with your email, or sign in if you already have an account.

Model interim-artifact-2026-10. How we estimate

How we estimate

This is an estimate, not a promise. It uses an interim model (interim-artifact-2026-10) built from the formulas in SaveWave's early prototype. The founder's original model will replace it when it is ready.

  1. Your window area and glass give how much heat the windows lose, plus a share for drafts.
  2. We assume well-fitted film cuts the glass loss (single pane from 1.00 to 0.55, double pane from 0.50 to 0.36) and about three quarters of the drafts around the windows it covers. Both come from SaveWave's prototype and still need checking against product tests.
  3. Your ZIP code's heating degree-days say how cold the season is. A simplified allowance has your heating cover 85% of it, with sun, people and appliances doing the rest; your home may differ.
  4. Your fuel's heat content, your heating system's efficiency and your price turn that into money, fuel and CO₂. CO₂ counts only the fuel burned at home, or an approximate New England grid average for electricity, which may differ elsewhere. It leaves out making the kit and the fuel's supply chain, and wood pellets' CO₂ isn't counted.
  5. The model assumes ordinary clear glass without storm windows, and a full heating season with the film up. Newer coated windows may save less, and film usually lasts one winter. Savings are before the cost of the kit.

Climate: historical heating degree-days by ZIP code, imported from SaveWave's prototype, which describes them as NOAA 1981–2010 normals; we are checking that source and moving to NOAA's current 1991–2020 normals. Prices: Maine's heating-fuel survey of October 5, 2026; gas and electricity are rounded examples from its published ranges.

The numbers behind this estimate

These are the interim model's assumptions, taken from SaveWave's prototype. They still need checking against the founder's original model and product tests.

Heat saved = window area in square feet × the drop in heat loss per degree × heating degree-days × 24 hours × 85%. Heating degree-days add up how far each day's average temperature falls below 65°F.

Heat loss through the glass, in Btu per hour per square foot per °F: single pane 1.00 before and 0.55 with film; double pane 0.50 before and 0.36 with film.

The draft allowance adds 0.08 for fairly tight windows, 0.22 for average ones and 0.45 for drafty ones; fitted film leaves 25% of it.

Fuel assumptions
FuelHeat per unitEfficiencyCO₂ per unit
Heating oil138,500 Btu per gallon83%10.16 kg per gallon
Propane91,500 Btu per gallon85%5.74 kg per gallon
Natural gas100,000 Btu per therm90%5.31 kg per therm
Kerosene135,000 Btu per gallon83%10.15 kg per gallon
Electric baseboard3,412 Btu per kWh100%0.25 kg per kWh
Heat pump3,412 Btu per kWh2.6 units of heat per unit of electricity0.25 kg per kWh
Wood pellets16,400,000 Btu per ton80%not counted

Efficiencies and CO₂ factors are fixed assumptions, not measurements of your heating system. Electricity uses an approximate New England grid average.