Put time next to watts.
Power describes a rate at a moment. Energy adds that rate over time. At constant power, energy in Wh = W × hours; divide Wh by 1,000 for kWh. An illustrative 120 W load for five hours uses 600 Wh, or 0.6 kWh.
Duty changes energy, not the running rating.
For an intermittent load, multiply by the share of time it runs. A hypothetical 100 W appliance available for 24 hours at 40% duty uses 960 Wh/day. That assumption does not turn its running requirement into 40 W. Its actual behavior needs measurement or documentation.
Keep three questions apart.
Your daily Wh budget, concurrent running W, and starting W answer different questions. Adding appliance energy does not establish whether an inverter can start a motor. Unknown starts stay unresolved. The load planner models one device starting while other marked loads run; it does not simulate every simultaneous start.
Keep these distinctions.
- W and kW are power; Wh and kWh are energy.
- Quantity, time and duty determine a daily energy assumption.
- Power and starting capability still need separate checks.
TRY THE REASONING
Practice with visible assumptions.
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Sources & learning scope
Source concepts reviewed 2026-11-07. Exercise values are explicitly illustrative. This path explains concepts and arithmetic; it is not an installation design or professional certification.
- EIA: measuring electricity
Power, energy, W/kW and Wh/kWh.