The average U.S. home uses about 900 kWh per month. So, that is 30 kWh per day or 1.25 kWh per hour. Your average daily energy usage is your target daily average in order to calculate your solar needs.
- Daily power consumption:
Daily power consumption = wattage rating x time in hours
2,000 watts x 3 hr = 6,000 watts-hour - Monthly power consumption:
Monthly power consumption = wattage rating x time in hours
2,000 watts x 3 hr x 30 days = 180,000 watts-hour
Your household energy use
Every electronic device in your home contributes to your monthly electric bill and annual energy use. By calculating the kWh usage of various devices, you can spot the culprits when your electric account (that is, your bill) runs high.
To calculate the daily kWh requirements of any device, start by finding its wattage. Usually, the device will have a label that includes kW information. If not, you can find it in the owner's manual. Once you know that wattage, determine how many hours the device is running in a day. Then, multiply the watt number by the number of hours the device is in use.
For example, if you use a 100-watt light bulb for 10 hours/day, the energy use = is 1 kWh:
100 watts x 10 hours = 1,000 watt‐hours = 1 kWh
However, does that lamp need to be on for 10 hours? You may only need the light from 7:00 pm to 11:00 pm. In that case:
100 watts x 4 hours = 400 watt‐hours = .4 kWh.
If you turn the lamp off when you leave the room, you will save electricity.
Repeat that simple calculation for all the devices in your home. Add them together, and you woill have your total daily kWh usage. Then multiply that daily usage number by the number of days in the month to calculate your monthly use.
kWh = money
Your utility bill tells you how much your power company charges per kWh. Multiply that amount by your daily, monthly, or annual kWh usage, and you will see how kilowatt-hours translate directly into expense.
With this calculation, you can also fine-tune your annual budgeting process by applying your new understanding of your typical electrical usage and how it varies over a year.
KWh usage for common household items
We have seen that burning a 100-watt light bulb for 10 hours expends 1 kWh. The calculation is roughly the same for 10 hours of TV viewing. For that same 1 kWh, you could listen to the radio for 20 hours.
We have done some other calculations for you, as examples of typical household energy use:
Dishwasher – NON-energy-efficient: up to 2.17 kWh/load
Dishwasher – energy-efficient: 0.5 kWh/load
Regular oven: 2.3 kWh/hour
Microwave oven: .12 kWh for a 5-minute heat session
Refrigerator – 1990s frost-free, 15 cubic feet: 150 kWh/month
Refrigerator – Energy Star 17 cubic feet: 35 kWh/month
Washing machine – Hot wash, warm rinse: 4.5 kWh/load
HE Washing machine – Cold wash/cold tinse: 0.3 kWh/load
Desktop computer: 0.06 ‐ 0.25 kWh/hour
Laptop computer: 0.02 ‐ 0.05 kWh/hour
Electric furnace with fan: 10.5 kWh/hour
Electric water-heater: 380-500 kWh/month
1,500 W portable electric heater: 1.5 kWh/hour
Central A/C (3-ton, 12 SEER): 3 kWh/hour
Ceiling fan: .075 kWh/hour