Home Energy Savings Calculator: Which Upgrade Pays Back Fastest?

Pick upgrades, enter your bills, and compare payback, lifetime savings and CO2 cut.

Project Details
Enter your measurements and requirements

Not sure where the energy goes? Do the home energy audit first.

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Upgrades to compare

Typical: 10 to 15% of heating and cooling. Lasts about 30 years. Size it

Typical: 10 to 20% of heating and cooling. Lasts about 20 years. Size it

Typical: 8 to 10% of heating and cooling. Lasts about 10 years.

Going solar? Use the solar calculator for production and payback.

Results
Calculated estimates for your project

Fastest payback

Smart thermostat

1.3 yr payback, $149 saved in year one, $1,506 net over 10 years.

UpgradePaybackPer yearLifetime net
Smart thermostat1.3 yr$149$1,506
Air sealing3.1 yr$187$4,430
Attic insulation to R4912.1 yr$168$5,593
$030 yr0
Smart thermostatAir sealingAttic insulation to R49
ROI over its life
753%
NPV at 3%
$1,245
Energy saved a year
424 kWh, 53 therms
CO2 avoided a year
963 lb
Equivalent to
7 months of free energy bills over its life

Turn these numbers into a build plan.

  • $200 net cost
  • $149 year-one savings
  • 1.3 years payback

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Insulation CalculatorSolar Panel Calculator

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Project plan · built from your numbers

Smart thermostat: save about $149 a year

Smart thermostat for $200 after rebates should save about $149 in the first year (5.4% of a $230 monthly bill) and pay back in 1.3 years. Log each month's bill to check the savings actually show up.

Materials
$200
Time
1 weekend
Level
Easy
6 steps 3 tools 3 materials
  1. 1

    Read 12 months of bills

    Note kWh and therms per month so you have a baseline to compare against.

    • Electric kWh by month
    • Gas therms by month
    • Current rates
  2. 2

    Line up rebates before buying

    Utility and state rebates usually need pre-approval or a listed contractor. Federal 25C and 25D credits ended for work completed after 2025.

  3. 3

    Check for a C wire

    Most smart thermostats need constant power. Use the adapter if there is none.

01 · Your numbers
Net cost
$200
Year-one savings
$149
Payback
1.3 years
CO2 avoided
963 lb a year
02 · The plan

6 steps · 3 tools · 3 materials

3 more steps, the full tool list and a shopping list you can check off as you go.

03 · Finished

Your plan is 60% built. Save it.

3/5

Smart thermostat: save about $149 a year

Finished in 1 weekend · $200 DIY

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Typical payback by upgrade

Typical installed cost, no rebates, $150 electric and $80 gas per month, prices rising 3% a year
UpgradeTypical savingsCostSaves per yearPaybackLasts
LED lighting75% of lighting electricity$150$1261.2 years15 years
Smart thermostat8 to 10% of heating and cooling$200$1491.3 years10 years
Air sealing10 to 20% of heating and cooling$600$1873.1 years20 years
Duct sealingUp to 20% of HVAC energy$700$1674.0 years20 years
Heat pump water heater (vs electric tank)About 60% of water heating$2,500$19810.9 years13 years
Attic insulation to R4910 to 15% of heating and cooling$2,400$16812.1 years30 years
Heat pump (vs furnace or resistance)30 to 50% of heating$12,000$336longer than it lasts15 years
Window replacement7 to 15% of heating and cooling$12,000$149longer than it lasts30 years

How the payback math works

Simple payback = (cost minus rebates) / first-year savings.

Energy prices rise, so the calculator grows the savings by the escalation rate each year (year n saves first-year savings x 1.03 to the power n minus 1) and counts years until the running total covers the net cost. Savings stop when the upgrade wears out, so a 10 year thermostat never earns a 30 year total. NPV discounts each year back to today at your discount rate.

Worked example: attic R19 to R49

  1. The house. 2,000 sq ft, gas heat, $140 electric and $110 gas a month.
  2. The savings. Attic insulation saves about 4% of the electric bill and 10% of the gas bill: $199 the first year, 91 therms and 395 kWh.
  3. The payback. $2,400 / $199 = 12.0 years simple payback, 10.4 years with 3% price growth.
  4. With a $600 utility rebate. 8.1 years, and $7,677 net over the insulation's 30 year life.

Houses with R11 or less in the attic save more, often two to three times as much. Hot south and west windows? Shade them first with the window overhang calculator. Size the job with the attic insulation calculator and check walls with the wall R-value calculator.

How to read your utility bill

Look for usage in kWh (electric) and therms or CCF (gas; 1 CCF is about 1.04 therms), and the total charge for the month. Your all-in rate is the total divided by the usage, which includes delivery charges. Ignore the fixed customer charge when estimating savings, since an upgrade does not change it. Use a 12 month average so a cold January does not skew the result.

Rebates and incentives in 2026

The federal 25C and 25D tax credits ended for upgrades placed in service after December 31, 2025. What remains is local: utility rebates for heat pumps, heat pump water heaters, insulation and smart thermostats, state programs, and the IRA HEEHRA and HOMES rebates in states that run them. Most require approval before the work starts. Search DSIRE by ZIP code and enter the total as rebates above. The energy audit cheat sheet shows where to start.

Energy savings calculator FAQ

What energy upgrades have the best payback?

With typical costs on a $150 electric and $80 gas monthly bill: LED lighting pays back in 1.2 years, a smart thermostat in 1.3 years, and air sealing in 3.1 years. Windows rarely pay back on energy alone.

Are federal tax credits still available for energy upgrades?

No, for work finished after 2025. The 2025 budget law (the One Big Beautiful Bill Act) ended the 25C energy efficiency credit and the 25D residential clean energy credit for property placed in service after December 31, 2025. Utility rebates, state programs and, where your state runs them, the IRA HEEHRA and HOMES rebates still apply. Search DSIRE (dsireusa.org) for your ZIP code.

How much can I save with a heat pump?

Against electric resistance, oil or propane heat, 30 to 50% of heating cost. Against cheap natural gas the savings are smaller and can be zero; enter your own gas and electric rates and a savings percent from your contractor's estimate.

Is it worth upgrading windows for energy savings?

Rarely on energy alone. At $12,000 for a house of windows, saving 7 to 15% of heating and cooling, payback is longer than it lasts. Replace windows for comfort, noise or rot, and do air sealing and attic insulation first.

How do I estimate the savings percent?

Start from the preset, then adjust with an energy audit or a contractor's modeled estimate. A blower door test shows how leaky the house is, which is the best predictor for air sealing and insulation savings.

How does solar payback work?

Solar is sized from your kWh use and sun hours rather than a percent of the bill. The solar calculator handles production, net metering and payback; without the federal credit, typical payback is 9 to 14 years.

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Calculate effective thermal resistance with thermal bridging

Related cheat sheets

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Home Energy Savings Audit

Complete guide to identifying energy waste and reducing power bills through efficiency improvements

Insulation R-Value Guide

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Weatherstripping & Air Sealing Guide

Weatherstrip types by application, door sweeps, foam sealants, and priority sealing locations

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