If a solar panel is a .5kW system, what length of time is it putting out that much power? Every hour?
Power = work done/time taken In other words, Watts=Joules/second. In this respect, power is a little like speed (m/s). Your question is looking at a car with a 50mph top speed, and asking how long is it going that fast? The solar panel will produce .5KW for as long as you require it. Enough to boil a kettle, run a modest electric heater etc,
Solar panels are rated under standard test conditions (STC), a certain amount of light at a certain distance, at a certain temperature, etc. A kW, or kilo watt, is 000 watts. So for the amount of time that the sun meets those conditions, the rate of output is 500 watts. An average location has an average of 5 sun hours a day, the total time that you produce the rated output. Watts is a rate, like miles per hour (mph), how fast it is going. Watt hours, or kilo watt hours (kwh) is a quantity, like miles. So if you drive 50 mph for 5 hours, you went 250 miles (50 mph x 5 hours). If you produce .5kw for 5 hours, you have the potential to produce 7.5kwh a day. Multiply that by 30 days in a month, you get 225kwh a month. In reality you will lose about 30% of the rated power from less than ideal weather, system losses, etc., so it's more like 50kwh a month. You can look at your electric bill to see how many kwh you use a month, maybe around 000kwh, and see what percentage of your usage a system like that can power.
I think it refers to the maximum power it is capable of. Of course, it won't really have this output because it's energy output (kWh) is dependent on it's energy input...
