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Energy Savings Calculator

Compare an old device against a new one and see the annual savings, payback period, CO₂ avoided and lifetime savings. Works for bulbs, appliances, HVAC — anything that draws power.

Annual savings

$14/ year
Per month$1.16
Payback 1.4 yr
Old$16/yr
New$2/yr
kWh saved / yr93
CO₂ avoided / yr37 kg
Lifetime savings$189

Calculations happen in your browser. Nothing is sent or stored.

How to use the Energy Savings Calculator

  1. Find both wattages. Check the label or spec sheet for the old device and the replacement — power draw is in watts (W) or kilowatts (kW). For appliances with variable load, use the average rating.
  2. Estimate daily use. Be honest about actual run time. Eight hours for a fridge compressor adjusted for duty cycle, four to six for lights, a couple for a TV.
  3. Enter your electricity rate. The price per kWh on your utility bill. US average is around $0.15/kWh; if you don't have your bill handy, use that as a first estimate.
  4. Add the upgrade cost and lifetime. How much you'd pay to switch (parts + install if relevant) and how long the new equipment is expected to last. Both feed the payback and lifetime savings numbers.
  5. Read the result. Annual savings is the headline. Below: monthly savings, payback period, kWh and CO₂ avoided per year, total savings across the equipment lifetime.

How is energy savings calculated?

The calculator runs both devices through the same daily-use formula, then compares. Power in watts × hours per day ÷ 1000 gives kilowatt-hours per day; times 365 gives the annual figure; times your rate gives the yearly cost. 

kWh/year   = watts × hours/day × 365 / 1000
cost/year  = kWh/year × $/kWh
savings/yr = old_cost − new_cost
payback    = upgrade_cost / savings/yr
lifetime$  = savings/yr × lifetime − upgrade_cost
CO₂/yr     = kWh_saved × 0.4 kg/kWh   (global grid average)

Examples

  • LED vs incandescent bulb: 60W → 9W, 5 hr/day, $0.15/kWh, $20 to swap, 15-year LED life. Savings ≈ $14/yr, payback ≈ 1.4 years, lifetime savings ≈ $190. Multiply by every bulb in the house.
  • Old fridge vs Energy Star: 600W effective vs 400W, 8 hr/day equivalent, $0.15/kWh, $1,200 upgrade, 15-year life. Savings ≈ $88/yr, payback ≈ 14 years — worth it only if the old one is on its last legs anyway.
  • Heat pump vs electric resistance heater (winter only): 1500W → 500W effective, 6 hr/day for 5 months ≈ 2.5 hr/day average annual, $0.18/kWh, $4,000 install, 15-year life. Savings ≈ $165/yr, payback ≈ 24 years — usually paired with cooling savings to make the math work.

FAQ

How accurate is this calculator?

Within 10–15% of reality for most appliances. The variance comes from inconsistent daily use, devices that draw less than their nameplate rating, electricity rate changes and standby power. Treat the result as a sanity check, not a guarantee.

Where do I find a device's wattage?

Check the label on the back or bottom of the device, the spec sheet on the manufacturer's website, or the EnergyGuide tag for US appliances. Light bulbs print the wattage on the box. For devices with variable draw (HVAC, fridges), a kill-a-watt meter gives the most accurate reading.

What is a good payback period?

For lighting and small appliances, anything under 2 years is a no-brainer. For HVAC, water heaters and bigger purchases, 5–8 years is typical and still worthwhile if the equipment lasts 15+ years. Anything over 10 years is hard to justify on savings alone — you're paying for comfort or environmental impact too.

How is the CO₂ saving calculated?

The calculator multiplies kWh saved by 0.4 kg CO₂ per kWh, a rough global grid average. The US is about 0.39, the EU about 0.25, and grids relying heavily on coal can be 0.7+. If you want a precise figure for your country, multiply your kWh saved by your local emissions factor.

Does this work for solar panels?

Yes, with a twist: treat the solar system as the "new" device with effective wattage 0 (no grid draw) and the existing usage as the "old". Enter the kWh you currently consume during the day, then your installation cost as the upgrade cost. The result is an apples-to-apples savings versus your grid bill.

What is the average electricity rate?

In the US, $0.15/kWh is the residential average as of 2024, but it ranges from $0.10 in low-cost states to $0.40+ in Hawaii and California. In Europe, $0.25–0.40/kWh is typical. Your bill will show the exact rate — use that number for an accurate calculation.

Privacy

Every calculation runs in your browser. Your numbers never leave your device — nothing is sent to a server, nothing is stored in cookies, nothing is logged. Close the tab and everything is gone.