# Watts to kWH per month

1. Dec 6, 2009

### Monocerotis

1. The problem statement, all variables and given/known data
The question asks for us to go around our house, figure out the power usage of different devices, based on the estimated time use of these devices and calculate the total power usage per month.

2. Relevant equations
Energy = Power X Time
Power = kW
Time = hours

3. The attempt at a solution
Example

Samsung TV
Power usage @ 130.65W
Usage @ 60 minutes per day (1 hour)

(0.13065 kW)(1 hour) = 0.13065 kWh

(0.13065 kWh)(31 days) = 4.05015 kWh per month

Is that the correct way in trying to determine a given devices power consumption per month ?

2. Dec 6, 2009

### Redbelly98

Staff Emeritus
Looks good.

3. Dec 6, 2009

### Pengwuino

Remember, when you multiply by 1 hour, what you're actually saying is it runs for 1 hour per day and thus takes 0.13065 kWh/day. If it ran for 8 hours, you'd instead have 8 hours * 0.13065kW per day giving around 1kWh/day.

4. Dec 6, 2009

### Monocerotis

yeah, that's what I've been doing for devices I have listed that run longer than an hour

for example our washing machine

1200W - 210 minutes @ 4 days per month

1.2kW x 3.5h = 4.2 kWh

4.2kWh x 31 days = 130.2 kWh/month