Watts to kWh calculation formula
E(kWh) = P(W) × t(h) / 1000
The energy E in kilowatt-hours (kWh) is equal to the power P in watts (W), multiplied by the time period t in hours (h), divided by 1000.
kWh = W x h / 1000
kilowatt-hour = watt x hour / 1000
Power (P) = 300W
Time period (t) = 2h
Energy (E) = 300W x 2h / 1000 = 0,6kWh