LED vs Incandescent Savings Calculator
How this LED vs incandescent savings calculator works
This calculator compares the total cost of running an LED bulb versus an incandescent bulb for the same light fixture. It combines both energy costs and bulb replacement costs so you can see real-world savings and how quickly a new LED pays for itself.
To use it, enter:
- LED wattage and incandescent wattage for bulbs that provide similar brightness.
- Hours used per day for the light (average over a year).
- Your local electricity rate in $/kWh (from your utility bill).
- Bulb purchase prices for the LED and incandescent options.
- Rated lifespans in hours for each bulb type.
The tool then estimates yearly and long-term costs for both options and calculates how many months it takes for the LED to recover its extra upfront cost through lower bills.
Energy cost formulas
Electricity providers usually bill in kilowatt-hours (kWh). A kilowatt-hour is one kilowatt (1,000 watts) used for one hour. The basic steps are:
- Convert bulb power from watts (W) to kilowatts (kW).
- Multiply by hours of use per day to get daily kWh.
- Multiply by your $/kWh rate to get daily cost.
- Multiply by 365 to get annual cost.
If a bulb has power P in watts, is used h hours per day, and your electricity rate is r dollars per kWh, then:
where E is the daily energy in kWh.
where C is the daily energy cost in dollars.
The calculator applies these formulas separately to the LED and the incandescent bulb, then multiplies by 365 days to estimate yearly energy cost for each option.
Total cost of ownership (energy + bulb purchases)
Electricity is only part of the story. Incandescent bulbs burn out much faster than LEDs, so you end up buying and replacing them more often. To capture this, the calculator converts each bulbโs rated lifetime into an expected number of replacements over a year (or another comparison period).
If a bulb is used h hours per day, there are about h ร 365 operating hours per year. If its rated life is L hours, the number of bulbs required per year is:
where N is the expected number of bulbs consumed in one year. For an LED with a long lifetime, N may be well below 1; for an incandescent, it is often greater than 1.
If each bulb costs B dollars, the annual bulb purchase cost is:
Total annual cost for each bulb type is then:
The calculator performs this for both the LED and incandescent bulb and then reports the difference as your annual savings.
Interpreting the results
Once you enter your values and click the calculate button, you typically see several outputs (exact labels may vary):
- Annual LED energy cost โ estimated electricity cost for running the LED bulb for a year.
- Annual incandescent energy cost โ estimated electricity cost for the incandescent bulb.
- Annual bulb purchase cost for each type, based on lifespan and price.
- Total annual cost for each bulb (energy + bulb purchases).
- Annual savings โ how much you save each year by using the LED instead of the incandescent.
- Payback period โ how long it takes for savings to recover any extra upfront cost of the LED.
Positive annual savings mean the LED is cheaper to own and operate on a yearly basis. A shorter payback period (for example, 3โ6 months) indicates that the investment in an LED is recovered quickly.
Payback period formula
The payback period compares the extra upfront money you spend on an LED bulb to the annual savings it generates. If the LED costs BLED and the incandescent costs Binc, the extra upfront cost is:
If the calculator finds annual savings of Sannual dollars per year, the payback time in years is:
The calculator typically converts this to months:
If the annual savings are very large compared with the extra upfront cost, the payback period will be short. If the LED is only slightly more efficient or much more expensive, the payback period will be longer.
Worked example
The following example uses typical values for a household lamp:
- LED wattage: 10 W
- Incandescent wattage: 60 W
- Hours used per day: 4 hours
- Electricity rate: $0.15 per kWh
- LED bulb cost: $3.00
- Incandescent bulb cost: $1.00
- LED life: 15,000 hours
- Incandescent life: 1,000 hours
Step 1: Annual energy cost
LED: 10 W = 0.01 kW. Daily energy use: 0.01 kW ร 4 h = 0.04 kWh. At $0.15/kWh, daily cost = 0.04 ร 0.15 = $0.006. Annual energy cost = $0.006 ร 365 ≈ $2.19.
Incandescent: 60 W = 0.06 kW. Daily energy use: 0.06 kW ร 4 h = 0.24 kWh. Daily cost = 0.24 ร 0.15 = $0.036. Annual energy cost = $0.036 ร 365 ≈ $13.14.
Step 2: Annual bulb purchase cost
Annual operating hours: 4 h/day ร 365 ≈ 1,460 hours per year.
LED: 15,000 hour life, so expected bulbs per year = 1,460 / 15,000 ≈ 0.10. At $3 each, annual bulb cost ≈ 0.10 ร $3 = $0.30.
Incandescent: 1,000 hour life, so expected bulbs per year = 1,460 / 1,000 ≈ 1.46. At $1 each, annual bulb cost ≈ 1.46 ร $1 = $1.46.
Step 3: Total annual cost and savings
LED total annual cost: $2.19 (energy) + $0.30 (bulbs) ≈ $2.49.
Incandescent total annual cost: $13.14 (energy) + $1.46 (bulbs) ≈ $14.60.
Annual savings: $14.60 - $2.49 ≈ $12.11 per year by using the LED.
Step 4: Payback period
Extra upfront cost of the LED bulb compared with incandescent: $3.00 - $1.00 = $2.00.
With annual savings of about $12.11, payback time in years is $2.00 / $12.11 ≈ 0.17 years. In months, 0.17 ร 12 ≈ 2 months.
In other words, the higher purchase price of the LED bulb is recovered in roughly two months. After that, each additional month of use adds to your net savings.
Typical LED vs incandescent comparison
The example above is representative of many household situations. The table below summarizes the key figures for that scenario, assuming 4 hours of use per day and $0.15/kWh electricity.
| Metric | LED (10 W) | Incandescent (60 W) |
|---|---|---|
| Annual energy cost | $2.19 | $13.14 |
| Bulb replacements per year | 0.10 | 1.46 |
| Annual bulb purchase cost | $0.30 | $1.46 |
| Total annual cost (energy + bulbs) | $2.49 | $14.60 |
| Annual savings vs incandescent | About $12 per bulb per year | |
| Approximate payback period | Around 2 months | |
Your own results will differ based on your usage hours, local energy prices, and the specific bulbs you choose, but in most cases LEDs offer substantially lower total cost over time.
Assumptions and limitations
To keep the calculator simple and fast, several assumptions are built into the estimates. It is important to understand them before applying the results to real decisions:
- Constant usage pattern: The tool assumes the same number of hours per day every day of the year. Actual use may vary by season, weekday/weekend, or occupant behavior.
- Constant electricity rate: A single $/kWh value is applied across all hours. Time-of-use tariffs, tiered pricing, taxes, and fees are not modeled.
- Similar brightness: The comparison assumes the LED and incandescent bulbs provide roughly the same light output (lumens). If one bulb is much brighter, the cost per lumen may differ.
- Rated lifetimes: Manufacturer lifetime ratings (for example, 15,000 hours for an LED) are averages under controlled conditions. Actual life can be shorter or longer depending on switching frequency, heat, and fixture design.
- No discounting of future costs: The calculator does not apply present-value or inflation adjustments. All costs are expressed in todayโs dollars without considering future rate changes.
- Single fixture calculation: Results are for one bulb or one fixture. To estimate whole-home savings, multiply the savings per bulb by the number of similar fixtures.
- Maintenance labor not included: Any time or labor cost of changing bulbs (for example, in hard-to-reach locations) is not included, even though longer-life LEDs can reduce these costs.
- Thermal effects not modeled: The impact of bulb heat on heating or cooling loads (for example, incandescent bulbs warming a room) is not included. In many homes the effect is small compared with direct lighting energy use.
Because of these limitations, treat the outputs as useful estimates rather than precise forecasts. They are best used to compare relative options (LED vs incandescent, or different LED wattages) under the same assumptions.
When to adjust your inputs
To get the most realistic results for your situation, consider the following tips when entering values:
- Use your actual electric rate: Check a recent utility bill for the all-in cost per kWh, including delivery and supply charges, rather than guessing.
- Average your usage: If a light is used more in winter than summer, estimate an annual average (for example, 5 hours/day in winter and 3 in summer โ about 4 hours/day overall).
- Match lumens, not watts: When picking wattages to compare, choose bulbs with similar lumen output so you are comparing equivalent brightness levels.
- Use realistic lifespans: If you know your bulbs tend to fail faster than rated life, you can reduce the lifespan values to better reflect local conditions.
By adapting the inputs to your home or business, the calculator offers a clearer picture of the potential savings from upgrading to LED lighting.