How this LED savings calculator works
The only fair way to compare light bulbs is at equal brightness, measured in lumens. Pick a brightness class, from 250 lm (a small accent lamp) to 2,600 lm (a floodlight), and the type of bulb you have now: incandescent, halogen or CFL. The calculator fills in the typical wattage of that bulb and of an LED giving the same light, using the lumen-equivalence tables from EU ecodesign rules and ENERGY STAR. You can override both wattages with the figures printed on your own bulbs.
The wattage difference times the number of bulbs and the hours they burn each year gives the energy saved. That is converted into money and CO₂, and a second saving that most calculators forget is added on top: replacement bulbs you no longer buy. A halogen lasts about 2,000 hours, so at 3 hours a day you replace it every 22 months. An LED rated for 15,000 hours lasts around 14 years.
The optional advanced setting covers heat interaction: during the heating season, the waste heat from old bulbs slightly reduces your heating demand, so part of the electricity saving has to be bought back as heat. Leave it at 0 for a pure electricity comparison.
The formula
Bulbs avoided (money/yr) = bulbs × hours/yr ÷ life_old × price_old Heat penalty = kWh saved × heating-season share × heat cost per kWh Annual saving = kWh saved × electricity price + bulbs avoided − heat penalty Payback = bulbs × LED price ÷ annual saving
Worked example: 20 halogen bulbs
The defaults replace 20 halogen bulbs of 42 W (800 lumens each, the classic “60 W equivalent”) with 8 W LEDs used 3 hours a day.
Each halogen uses 46 kWh a year and costs €11.50 to run at €0.25/kWh. The LED uses 8.8 kWh and costs €2.19. Across 20 bulbs the switch saves 745 kWh a year, an 81% cut in lighting power, worth €186. Because the halogens would need replacing roughly every 22 months at €2.50 each, another €27 a year is avoided, for a total saving of €214 a year.
The 20 LEDs cost €60, so they pay for themselves in about 3 months. Over 10 years the cumulative cost of the halogen lighting reaches about €2,570 against roughly €500 for LEDs, a net saving of €2,075. The switch also avoids about 260 kg of CO₂ a year on a 350 g/kWh grid. At 3 hours a day the LEDs should last around 14 years.
How to read the results
- Savings per year combines electricity saved and replacement bulbs avoided.
- Energy saved and the percentage show how much lighting power falls.
- Payback is shown in months because it’s usually short. A long payback means the bulbs are rarely switched on.
- 10-year net saving includes the LED purchase and any LED replacements within the period.
- LED efficacy (lm/W) lets you judge bulb quality: below 80 lm/W is a weak LED, 100–150 lm/W is good.
- The bar chart compares the annual electricity of all four technologies at your brightness and usage.
Typical values
| Brightness | Incandescent | Halogen | CFL | LED |
|---|---|---|---|---|
| 250 lm | 25 W | 18 W | 6 W | 3 W |
| 450 lm | 40 W | 28 W | 9 W | 4.9 W |
| 800 lm | 60 W | 42 W | 14 W | 8 W |
| 1,100 lm | 75 W | 53 W | 18 W | 10.5 W |
| 1,600 lm | 100 W | 70 W | 23 W | 15 W |
| 2,600 lm | 150 W | 105 W | 42 W | 24 W |
Typical lifetimes: incandescent ~1,000 h, halogen ~2,000 h, CFL 6,000–10,000 h, LED 15,000–25,000 h.
Tips to save more on lighting
- Start with the lamps that burn longest: kitchen, living room, hallway, outdoor security lights. Rarely used lamps can wait.
- Replace GU10 and MR16 halogen spotlights. Kitchens often have 8–12 of them at 35–50 W each, and swapping them is usually the biggest single lighting saving in a home.
- Buy by lumens and colour temperature. 2,700 K is warm white like incandescent; 4,000 K is neutral for kitchens and offices. Check the dimming compatibility if you use dimmers.
- Add controls: motion sensors for hallways and outdoor lights, timers for decorative lighting.
- Don’t let lamps leak in standby. Smart bulbs draw 0.2–0.5 W even when off; see the standby power calculator.
- See the effect on your whole bill with the electricity bill calculator.
Limitations
Equivalent wattages are typical values; actual light output and efficacy vary between brands, and cheap LEDs may fall short of their claimed lumens or lifetime, especially in enclosed or hot fittings. The calculator assumes all bulbs burn for the same average hours; if usage differs strongly between rooms, run it separately for each group. Electricity prices are held constant over 10 years. The heat-interaction setting is a simple approximation and ignores the extra cooling load that old bulbs add in summer.
Method & assumptions
Energy saved = bulbs × (Wold − WLED) × hours/day × 365 ÷ 1000. Annual saving = kWh saved × price + replacement bulbs avoided (hours ÷ old-bulb life × price) − optional extra heating (kWh saved × heating-season share × heat cost). Payback = LED purchase ÷ annual saving.
Frequently asked questions
How much money do LED bulbs save?
What LED wattage replaces a 60 W bulb?
How long do LED bulbs last?
How long is the payback on LED bulbs?
Do incandescent bulbs help heat my home?
Are CFLs worth replacing with LEDs?
Sources & references
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