"Watt" is a rate of using energy.
"4 kW" means 4,000 watts.
"4 kW for 6 hours" means 4,000 watts for 6 hours.
If you use energy at the rate of 4 kW for 6 hours, then altogether you use
24 kilowatt-hours, or 24,000 watt-hours, or 86,400,000 joules.
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