What This Calculator Does
The Smart LED Bulb Energy Savings Calculator estimates how much money and electricity you save each year by replacing traditional incandescent or halogen bulbs with energy-efficient LED bulbs. LEDs use a fraction of the wattage to produce the same brightness, so the savings add up quickly — especially across multiple fixtures used for hours every day.
How to Use It
Enter the wattage of your old bulb, the wattage of the replacement LED, how many hours per day the light is on, the number of bulbs you plan to switch, and your electricity price per kilowatt-hour (kWh). The calculator shows your annual savings, the energy saved in kWh, the running cost of each bulb type, and a projected 10-year saving.
The Formula Explained
Energy use in kWh equals watts divided by 1000, multiplied by hours of use. Multiply the wattage difference between the old and new bulb by daily hours and 365 days, divide by 1000 to convert to kWh, then multiply by your cost per kWh and the number of bulbs:
$$\text{Annual Savings} = \frac{\text{W}_{\text{old}} - \text{W}_{\text{led}}}{1000} \times \text{hours/day} \times 365 \times \text{cost/kWh} \times \text{bulbs}$$
Worked Example
Suppose you replace a 60 W incandescent bulb with a 9 W LED, used 5 hours a day, with electricity at $0.15/kWh. The wattage difference is 51 W. Energy saved = $$\frac{51}{1000} \times 5 \times 365 = 93.075 \text{ kWh per year}.$$ At $0.15/kWh that is $13.96 per year per bulb — and roughly $139.61 over ten years.
FAQ
Does this include the cost of buying the LED bulb? No — it shows only energy savings. LEDs also last far longer, so you replace bulbs less often, adding extra savings not shown here.
Where do I find my cost per kWh? Check your electricity bill; it is usually listed as the unit rate or price per kWh.
Why use 365 days? The formula assumes daily use year-round. If a light is only used seasonally, adjust the daily-hours value to reflect an average across the year.
