If you have a 100 watt light bulb, is that a 100 watts per second, per minute? The answer is not "per" but a constant wattage over the period the light bulb is burning. A watt is a watt - you cannot divide it - it's a 100 watts when you flip the switch and still a 100 watts just before you flip it off. If you leave the light on 24 hours a day, then the energy used in one month will be 30x24x100 = 72,000 watt-HOURS. Not watts per (divided) hour but watts multiplied by hours.

If you want to know how many watts per hour or minute, you would first have to determine over what period the light bulb burns. To a utility company 72,000 watt-hours (or 72 kilowatt-hours) at a rate of 10 cents a kilowatt hour, $7.2 to burn that bulb all month.

If you want to know how many watts per hour or minute, you would first have to determine over what period the light bulb burns. To a utility company 72,000 watt-hours (or 72 kilowatt-hours) at a rate of 10 cents a kilowatt hour, $7.2 to burn that bulb all month.