What are watts, watt-hours, kilowatt-hours and amp-hours?
Watts measure the rate at which equipment uses or supplies power. Watt-hours and kilowatt-hours measure energy over time. Amp-hours measure electric charge and only describe comparable energy when the system voltage is also known.
Power and energy are different
A watt (W) is a unit of power: the rate at which a tool, appliance or charger is using or supplying energy at a particular moment. A 600 W appliance asks the power system to support a 600 W load while it is running. Check both the continuous output and any short starting demand when matching equipment to an inverter or portable power system.
A watt-hour (Wh) is a unit of energy. One watt-hour is the energy used by one watt for one hour. A kilowatt-hour (kWh) is 1,000 Wh. These units are useful for comparing stored energy with the energy your equipment needs during a shift.
Where amp-hours fit
An amp-hour (Ah) is a measure of electric charge, not a complete measure of energy. Voltage matters. Two batteries with the same Ah rating but different nominal voltages do not store the same nominal energy. For a first-pass comparison, nominal watt-hours are voltage multiplied by amp-hours. Use the product's stated Wh or kWh figure where one is available.
A simple runtime calculation is stored watt-hours divided by load watts. Treat the answer as a planning baseline, not a promise. Inverter losses, battery management limits, temperature, battery condition, cable losses and changes in the appliance's demand can reduce usable runtime.
What to check
Use watts to check whether the system can start and run the load. Use watt-hours or kilowatt-hours to plan how long the load needs to run. Use amp-hours only with the matching voltage and battery specification. Then confirm recharge time, connector compatibility and the manufacturer's operating limits before relying on the system on site.