Home Energy Savings Calculator: LEDs, Standby Power and Thermostat Setback
- By The Eco Aesthetic Editorial Team
- Posted
A saving is watts avoided, times hours, times 365, divided by 1,000 to give kWh, then multiplied by your electricity rate. Swapping ten 60 W bulbs that run 3 hours a day for ENERGY STAR LEDs saves about 547.5 kWh, roughly $99.59 a year at the 18.19 cent U.S. average. This calculator does that sum for LEDs, standby power and a thermostat setback.
Energy savings calculator
Fill in any of the three groups; leave the rest at their starting values or clear them. Results update as you type and the numbers are saved in the page address. Nothing leaves your browser.
Defaults in use: the U.S. average rate of 18.19 cents per kWh (EIA, January to August 2026, preliminary); LED efficacy of 80 lumens per watt, the ENERGY STAR minimum for bulbs under 90 CRI; 3 hours a day of lighting, the ENERGY STAR label basis; and 5 W of standby draw per device, a starting value inside the 1 to 20 W range. Change any of them to match your home.
How the energy savings calculator works
Every saving here is power avoided, multiplied by time, converted from watt-hours to kilowatt-hours and priced at your rate. The only choices are where each power figure comes from. For bulbs, the old wattage is printed on the bulb, and the LED wattage is estimated from the lumens ENERGY STAR requires and the efficacy it requires, so it is an upper bound and a real LED may draw less. For standby, the draw per device is yours to measure. For the thermostat, the calculator uses the Department of Energy's published upper bound and nothing else.
LED watts = lumens needed ÷ efficacy (lm/W) LED kWh saved = (old W − LED W) × bulbs × hours per day × 365 ÷ 1,000 standby kWh = devices × standby W × idle hours per day × 365 ÷ 1,000 thermostat saving ≤ 10% × yearly heating cost, only for a setback of 7 °F or more for 8 hours or more a day dollars = kWh × rate in cents ÷ 100 CO2 (kg) = kWh × 0.672
- lumens needed
- the lower end of ENERGY STAR's light output range for the incandescent wattage you are replacing
- rate
- cents per kWh; the U.S. average is 18.19
- 0.672
- kg of CO2 per kWh, EPA national marginal rate (eGRID 2022), a national default rather than your grid
Example: ten 60 W bulbs and six idle devices
Worked example
Given: 10 bulbs, 60 W, 3 hours a day; LED efficacy 80 lm/W; rate 18.19 cents per kWh; 6 devices at 5 W, idle 20 hours a day.
- LED watts at the ENERGY STAR minimum:
800 ÷ 80 = 10 W - Watts saved per bulb:
60 − 10 = 50 W - kWh saved per year:
50 × 10 × 3 × 365 ÷ 1,000 = 547.5 kWh - Dollars:
547.5 × 18.19 ÷ 100 = $99.59 - Standby draw, if all six were switched fully off:
6 × 5 × 20 × 365 ÷ 1,000 = 219 kWh = $39.84 - CO2 from the LED kWh:
547.5 × 0.672 = 367.9 kg
Answer: About 547.5 kWh a year ($99.59) from the bulbs, and up to 219 kWh ($39.84) if the standby draw is truly cut.
The figures behind the calculator
| Figure | Value | Source (accessed 2026-11-14) |
|---|---|---|
| Minimum lumens for an LED to replace 40 / 60 / 75 / 100 W | 450 / 800 / 1100 / 1600 | ENERGY STAR Lamps V2.1, section 9.2 |
| Minimum efficacy, omnidirectional lamps, CRI under 90 / 90 and up | 80 / 70 lm/W | ENERGY STAR Lamps V2.1, section 9.1 |
| Label usage basis | 3 hours a day | ENERGY STAR Light the Moment factsheet |
| Standby share of residential electricity | 5 to 10% | LBNL Standby Power FAQ |
| Standby draw of most appliances | 1 to 20 W | Meier and Rosen, LBNL, 1999 |
| Thermostat setback, upper bound | 10% of heating for 7 to 10 °F, 8 h a day | DOE, 2024-01-11 |
| U.S. average residential rate, Jan to Aug 2026 | 18.19 cents per kWh | EIA Electric Power Monthly Table 5.6.B (preliminary) |
| CO2 per kWh avoided | 0.672 kg | EPA GHG Equivalencies Calculator, eGRID 2022 |
State rates in the drop-down come from the same EIA table. Each is a January to August 2026 residential average.
Assumptions and limits
- The rate is a single flat cents-per-kWh figure. Time-of-use, tiered and demand pricing can change the dollars; the kWh do not change.
- LED watts are estimated at ENERGY STAR's minimum efficacy and minimum lumens. A better bulb draws less, so the saving shown is conservative. A bulb that cannot beat the old one at your inputs shows no saving rather than a negative.
- The standby group treats all idle hours as removable. Some devices (a router, a refrigerator, anything that keeps a schedule) should stay powered, so only list devices you can switch off.
- The thermostat line is shown only for a setback of 7 °F or more for 8 hours or more a day, and as the maximum DOE describes, applied to heating cost only. It does not extrapolate smaller setbacks.
- CO2 is calculated for electricity only, at the EPA national marginal rate. It is left out of the thermostat line because the heating fuel is unknown.
- Rates and constants are as published on the dates shown. EIA's 2026 monthly values are preliminary.
Frequently asked questions
How much do LED bulbs save per year?
It depends on how many bulbs you replace, their old wattage and how long they burn. With ENERGY STAR's minimum brightness and efficacy figures, a 60 W incandescent becomes an LED of about 10 W or less, so each bulb saves roughly 50 W. At 3 hours a day that is about 54.8 kWh per bulb per year. Multiply by your rate for dollars.
How do I calculate the cost per kWh?
Divide the electricity charges on your bill by the kWh used, or read the rate your utility prints. If the bill mixes delivery and supply charges, add them. The U.S. Energy Information Administration publishes state residential averages, and the calculator starts from one of them. Your own bill is more accurate, so type your rate into the field if it differs.
Which electricity rate should I use?
Use your own rate from your bill if you have it. If not, pick your state and the calculator fills in the EIA residential average for January to August 2026, which is 18.19 cents per kWh for the United States. Those 2026 values are preliminary, and time-of-use or tiered plans can differ, so treat the dollar figure as an estimate.
How much power do devices use on standby?
Lawrence Berkeley National Laboratory reports standby draw for most appliances of 1 to 20 watts in a 1999 study, and says standby is typically 5 to 10 percent of residential electricity use. Newer devices often draw less, so a plug-in watt meter on your own devices gives a better number than any average.
Does a thermostat setback really save money?
The Department of Energy says you can save as much as 10 percent on heating by turning the thermostat back 7 to 10 degrees Fahrenheit from its normal setting for 8 hours a day. That is an upper bound for one scenario. The calculator only shows it for a setback that matches, and it applies to heating cost, not your whole bill.
Are ENERGY STAR appliances worth the extra cost?
It is a payback question: extra purchase price divided by yearly savings. The ENERGY STAR label tells you a model meets EPA efficiency criteria, but it does not tell you your payback. Take the yearly kWh of the efficient model and the standard one from their spec sheets, multiply the difference by your rate, and divide the price premium by that saving. The formula on this page does the multiplication step.
Sources
- U.S. EPA ENERGY STAR Program Requirements for Lamps, Version 2.1 (light output and minimum efficacy) (energystar.gov) Sections 9.1 and 9.2. Accessed 2026-11-14.
- U.S. EIA, Electric Power Monthly, Table 5.6.B (average residential price by state, year to date through August 2026) (eia.gov) 2026 values are preliminary. Accessed 2026-11-14.
- Lawrence Berkeley National Laboratory: Standby Power FAQ, and Meier and Rosen (1999), Leaking electricity in domestic appliances (standby.lbl.gov) Companion paper: https://www.osti.gov/biblio/793734. Accessed 2026-11-14.
- U.S. Department of Energy: Celebrate National Cut Your Energy Costs Day (thermostat setback) (energy.gov) Accessed 2026-11-14.
- U.S. EPA: Greenhouse Gas Equivalencies Calculator, calculations and references (electricity avoided) (epa.gov) eGRID 2022 national marginal rate. Accessed 2026-11-14.