How much does it cost to use a Microwave oven vs an Electric oven vs gas oven?

Answer 1

Do the math, an electric oven uses 1500W for 20 minutes to heat one cup of coffee, a 700W microwave takes 2.0 minutes
so at about 35c per KWh the oven would cost 17.5c and the microwave would cost 0.82c.
Oh! just in case you don't know a KWh is 1000 watts of power going into your house for one hour for example, ten 100 Watt light bulbs switched on for one hour would cost 35 cents.
The gas oven would cost about the same as the electric oven because you have to heat all the metal around the oven walls.
So the oven is about 17 times more expensive than the microwave!