Q&A for How to Calculate Kilowatt Hours

Take a reading of your electric meter and write down the numbers. At the same time the next day, take a reading of your meter and write down the numbers. Then, compare the difference increased between both days—that will give you an average of what you used in the last 24 hours.

Oversimplified, multiply the current in amps shown on the meter by the voltage -- likely 120 -- to find watts. Ohm's law says Watts is equal to Volts times Amps in any DC circuit or purely resistive load on an AC circuit. A typical incandescent light bulb is a purely resistive load (contains no motor, electronics etc). A 120-volt light bulb that draws .833 amps is consuming 100 watts. AC circuits are in your home -- not DC. Many connected devices are not purely resistive so your calculated wattage many differ slightly that that actually used.

Volts x Amps x efficiency x hours / 1000

2 x 32 = 64 watts x 5 hours per day estimate usage = 320 watts. Multiplied by 365 days in a year = 116,800 watts, divided by 1000 (1000 watts is 1 kilowatt hour) = 116.80 kWh. 116.8 multiplied by your kWh cost (found on your utility bill) = annual cost of operating the item.

Unit of current = amps Unit of energy = KWh In simple terms, Energy (KWh) = Current (in Amps) x Voltage (in Volts) x Time (in hours) x 3.6

7.99 cents or, about 8 cents per KWH.

240V x 95A x 24Hr / 1000 = 547 KWH (assuming 240 volts for 24 hours) Half that for 120 volts.

Check the bottom of the base. It will tell you the power consumption in Watts.

It doesn't cost any less to run. The math is always volts x amps. Typically a motor running at 120 volts uses twice as much current in amps as the motor running at 240 volts. The cost of installation is less; it uses smaller wire so there is less copper, and costs less and is easier and faster to handle and install than a larger wire.

Kilowatts = amps x volts x efficiency = 8.7 x 230 x efficiency = 2001, or 2 KW. Efficiency is assumed in this example to be 100% (hence 1.0 in the formula, but in reality is lower). If the pump runs 30 minutes it has used 1 KWh, 1 hour = 2 KWh, if for 2 hours = 4 KWh, and so on. Multiply KWh rate ($) x KHw used to find total cost of operation. You will need your cost per kilowatt hour and gallon per minute of your pump.

A generator of that size would likely require pro installation and include an automatic transfer switch. The size of your service (for 200 amps, a 50 KW gen would be able to carry this load) assumes all these loads don't all come on at once.

Add all of the watts marked on the light bulbs. Take the total watts multiple hours on each day. Then divide by 1000. Take that answer and multiply it by the cost per kilowatt in your area (average is $ 0.12) that equals the price you are looking for.