kW, kWh and amps: the practical difference
A practical guide to power, energy and current for home electricity and EV charging.
Power and energy are not the same
Kilowatts (kW) describe the rate at which energy is transferred. Kilowatt-hours (kWh) describe an amount of energy. A 2 kW heater running for three hours uses 6 kWh.
Where amps fit
Amps measure current. Available power depends on current, voltage, supply type and power factor. In a European three-phase 400 V system, 16 A per phase is approximately 11 kW for a balanced resistive load.
Use the right number
Use kW when checking whether a charger or inverter can support a load. Use kWh when estimating energy cost, battery capacity or runtime. Electrical design must also consider cable installation, protection and local regulations.