How do you calculate the "watts"???

Question

Recently, I changed all my light bulbs to those enegy efficient "spiral" ones. It says that it only uses 13 watts but put out a "light energy" of a 40-watt bulb. My question is: if you leave the light on for 24 hours will it still consume just 13 watts for that whole 24-hour period? or they calculate it by hour. so if i say leave it for 24 hours, ive used 312 watts??? help...Im trying to cut down on my energy consumption...(its my small part of helping the global enviromental crisis :)

Answer 1

Generally, Voltage times the amount of Amps being used.

Volts X Amps = Watts

Watts / Volts = Amps

Watts / Amps = Volts

(This is ignoring Power Factor)

Answer 2

watt the heck?!

Answer 3

A Watt is a measurement of power.  You want a measurement of energy, which is generally a kilawatt-hour (kWh).

If you run a 13 Watt lightbulb for one hour, that's 13 Watt-hours (0.013 kWh).  If you run it for 24 hours, it's 13*24 = 312 Watt-hours = 0.312 kWh.

In comparison, for a 40 Watt bulb if you leave it on for 24 hours, you use 40*24 = 960 Watt-hours = 0.96 kWh.

So for every 24 hours your CFL is on, you've saved about 0.65 kilawatt-hours.

In terms of money, in the USA 1 kWh costs somewhere around 10 cents.