40 watts of electricity used everyday for a month will cost around 50 cents a month depending on your KWH electricity cost.
A KWH is 1,000 watts and in most places the cost per KWH or 1,000 watts of electricity used is around 10 to 15 cents.
Although in some locations a KWH can cost as much as 25 cents to 37 cents per KWH.
1000 watt per hour is called a kilo watt hour.
40 watt light bulb would use 40 watt per hour.
A kilowatt hour (kWh) is a measure of how much energy you're using per hour, whilst a kW is a measure of power.
kW stands for kilowatt, a universal standard for measuring electricity. So, one kilowatt equals 1,000 watts.
Your electricity provider charges by how much electricity you use per kilowatt hour (kWh).
The kilowatt-hour is a unit of energy equal to one kilowatt of power sustained for one hour and is commonly used as a measure of electrical energy.
One kilowatt-hour is equal to 3600 kilojoules.
Here's the Formula for Calculating Watts Into Kilowatt-Hours: kWh = (watts × hrs) ÷ 1,000.
One kilowatt is equal to 1,000 watts, so to figure out the kWh per day that your refrigerator uses, you simply need to divide the watt-hours per day (7,200) by 1,000 for a total of 7.2 kWh per day.
Example: 7,200 watt-hours per day / 1,000 = 7.2 kWh per day.
1000 kWh is not far off the US monthly average for a typical home, which is 900 kWh/month.
This equates to about 30 kWh per day.