It costs more than you think to run a light bulb!
Did you ever wonder how much it really costs to run something electrical?

You need 3 pieces of information:

1) How many watts your item uses.
2) How long you use it, in hours.
3) Your local cost for electricity, per KWH, or Kilowatt-Hour, as shown on your electric bill. (Ranges from about 8 - 15 cents.)

Watts X Time / 1000 X Cost per KWH = Total cost.

Let's use a regular 100 watt light bulb for example, lit continuously for one year (8760 hrs.), at a cost of 12 cents per KWH.

100 watts times  8760 hrs. = 876,000 divided by 1000 (converts to KWH) = 876 KWH times 12 cents = $105.12.

A large appliance like an electric range might be rated in Kilowatts (KW) instead of watts. In that case, you can skip the /1000 in the formula, as we are already working with kilowatts, instead of watts.

Example: 12.5 KW X 2 hrs. = 25 KWH X 12 cents = $3.00.

A Kilowatt-Hour (KWH) means using 1000 watts of electricity for 1 hour. The power company charges you for each KWH you use. Ten 100-watt light bulbs lit for one hour would equal 1 kilowatt hour, or one 100 watt bulb lit for ten hours would equal 1 kilowatt-hour. In the above example, the watts times hours = Watt Hours. The divide by 1000 converts this into Kilowatt-Hours.


A regular old-fashioned light bulb uses whatever wattage it is rated at, 60 watts, 100 watts, etc. Newer "Compact Fluorescent" or "LED" light bulbs use much less power for a given amount of light. In this case, you have to use the wattage that the bulb actually uses, NOT the "equivelent" wattage. A compact fluorescent might be labeled "100 watt equivelent, using only 20 watts"

Many household appliances have their wattage ratings listed on the unit, often near where the power cord enters the unit. This is usually a maximum rating, not all appliances use the max wattage all the time. A coffee maker will use the max watts while brewing, but much less wattage to keep the coffee warm afterwards. A fan on low speed will use less than max. Your electric range might use 12 KW, but that's with all the burners and the oven on high.

If your appliance does not list watts, but instead lists volts (V) and amps (A), you can get an approximate wattage rating by multiplying the two numbers.

Example: 120V times 8A = 960 watts.

For electric motors up to 2 horsepower, you can approximate 1000 watts per horsepower. Larger motors, as well as some high-efficiency smaller motors, can get by with about 800 watts per horsepower. Watch out for
fake horsepower ratings!

Example: 1/4 horsepower motor = 250 watts.

Some large television sets can use several hundred watts of power. So if you're a couch potato, add it up! Better yet, turn off the TV and spend more time studying!

A common street intersection with 3 traffic signals aiming in each direction, has twelve 150 watt bulbs lit at any given time. Thats 1800 watts. At 12 cents per kilowatt hour, it costs 21.6 cents per hour, times 8760 hours in a year, comes to $1892.16 Or about $158.00 a month. Walk signals not included! Luckily, new (and expensive) L.E.D. lights use about one-tenth of the power.

Near my hometown, several communities think it's necessary to "light up" their water towers at night. Kaukauna appears to have four 1500 watt lights, and Little Chute appears to have six 1000 watt lights. In either case, thats 6000 watts on each tower. At 12 cents per kilowatt-hour, that's 72 cents per hour, and at 10 hours per day, $7.20 a day, times 30 days equals $216.00 a month, each. That's about
twice the electric bill for my whole house! And we're supposed to go out and buy expensive light bulbs to save 50 watts! Of course I do, because I have to WORK for my money. But I imagine that the water tower lights are paid for with tax dollars. Easy come, easy go!

Of course the most important thing is that the share holders of the power company make a lot of money. So the more you save energy, the more they will keep increasing the rates! That's how it works.

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