How to Calculate Lighting Kw
- 1). Make a list of all the lights in your household, noting both the wattage of each and the estimated amount of time in hours per month it is used. Extrapolate from an estimated daily figure by multiplying it by 30 if you need to.
- 2). Add the total wattage for all the bulbs and divide by 1,000 to get the kW for the lighting in the home.
- 3). Multiply the wattage of each bulb by the hours used, add the total and divide by 1,000 to get the kWh used monthly.
- 4). Multiply your total kWh by the cost for a kWh of electricity from an electric bill. If your total kWh usage is 300, and your cost per kWh is 15 cents, your electric charge for your lights is $45 per month.