# 220 volts If a 1000-watt HPS lamp using 110 volts were switched to 220 volts, thus using fewer amps, how would you figure out the amount of electricity saved?
High Electric,
Iowa

The formula for figuring watts, the unit the electric company measures, is A x V = W. Another permutation of this formula is A = W/V (A = amperes, think of it as the amount of electricity; W = watts, think of it as the pressure; V = volts).

A 1000-watt lamp uses 1000 watts, or 1 kilowatt plus the electricity to run the ballast, say 250 watts. That is a total of 1250 watts. Dividing by the voltage (110) shows that the lamp uses about 11.36 amperes of electricity. Running at 220 volts, with the pressure doubled, only half as much electricity is needed to do the same work so the system uses about 5.68 amperes.

Either way, each hour, it uses 1250 watts, or 1.25 kilowatt hours. Readers with grow questions (or answers) should send them to Ed at: Ask Ed, PMB 147, 530 Divisadero St., San Francisco, California 94117, USA
You can also email Ed at [email protected], and send queries via his website at www.ask-ed.net.
All featured questions will be rewarded with a copy of Ed’s Marijuana Question? Ask Ed. from Quick Trading.
Sorry, Ed cannot send personal replies to your questions.