Austin Energy Solar Rebate Program
A watt is a unit measuring power, the rate of energy consumption. The number of watts being used at any instant can be computed by multiplying the voltage by the current. A light bulb which draws 2 amperes of current from a 115 volt outlet is using 2 times 115 = 230 watts of power. If the light is on for one hour, it consumes 230 watt-hours of energy. A kilowatt-hour is a 1000 times larger unit of energy typically used to calculate our electric utility bill. The light bulb above uses 0.23 kilowatt-hours of energy if it is on for one hour. It uses 1.15 kilowatt-hours if it stays on for 5 hours. Kilowatt-hours are abbreviated as kwh.

Each kilowatt-hour of energy in Austin costs only about 7 cents for the first 500 kwh's that you use. There is also a variable fuel charge that is included in the above figure. As you use more than the 500 initial kwh, the charge goes up to about 11 cents per kwh. If we assume your electric bill is considerably more than 500 kwh's per month, then the kwh cost we should use is about 11 cents. Check your electric bill or talk to Austin Energy to get a more accurate number.

Incidentally, at the peak of the energy blackout crisis in California, the cost per kwh was as high as 75 cents. Even today, the cost in California is several times higher than in Texas. It is also much higher in foreign countries. That is why Germany and Japan, for example, are quickly moving toward the use of solar energy.