The unit kilowatt-hour is actually used to express the electrical energy used. In order to convert from energy to power, we use the formula:
Power = Energy / time
In 30 days, with a daily consumption for 16 hours, the total consumption time will be 30 * 16 = 480 hours
The power usage is:
Power = 300 / 480
The average power usage is 0.625 kilowatts or 625 watts.