ENERGY CONSUMPTION PER DAY
Watts x Hours of Use = Watt Hours / 1000 = kWh
For instance, 60 watts x 3 hours per day = 180 watt hours per day. 180/1000 = .18 kWh per day.
Now multiply by the number of days the bulb is used per year. In the example above, let's say the bulb is used 365 days per year. So now you get .18 x 365 = 65.7 kWh per year.
Now multiply by your cost of electricity per kWh, as seen on your energy bill. Don't forget to include delivery costs, which are often listed separately.
15 cents = .15 x 65.7 kWh = $9.86
Although your hours of use and cost of energy may be different, whatever numbers you choose for those will remain the same when replacing old lights with LED lights. The only factor that changes when installing LED lights is the wattage used to produce the light you need. An easy way to convert the cost of the old bulb to the cost of an LED is this:
(Annual Cost of Previous Bulb x LED Wattage) / Previous Bulb's Wattage
For example, if you're replacing a 60 watt incandescent bulb ($9.86 per year) with a 10 watt LED:
($9.86 x 10 watts) = $98.60 / 60 watts = $1.64. This is the annual cost of the 10 watt LED bulb. Much less than the $9.86 of the 60 watt incandescent bulb!
Now if that's still confusing, you can simply plug all your factors into our handy dandy energy savings calculator and forget about having to carry the one. (Image below links to our calculator online.)