Quick answer: Check three separate requirements: simultaneous running watts, any startup demand and the energy needed over time. Output in watts answers what can run; capacity in watt-hours answers how much energy is stored. A large capacity cannot compensate for an inadequate output limit.
Write a load worksheet
| Example device | Assumed average watts | Hours | Energy |
|---|---|---|---|
| Laptop | 40 W | 4 | 160 Wh |
| Network equipment | 12 W | 4 | 48 Wh |
| LED light | 5 W | 4 | 20 Wh |
| Total | 57 W if all run together | 228 Wh |
These are invented planning inputs, not measured product values. Replace each with your own measured load or a suitable manufacturer specification. Energy equals average watts multiplied by hours. A cycling appliance needs an average over its operating cycle, rather than continuous use of its peak rating.
Add reserve and conversion losses explicitly
With a chosen 20% planning reserve, the example needs 228 × 1.2 = 273.6 Wh delivered to the loads. If you then assume that 80% of nominal stored energy reaches those loads, nominal capacity would be 273.6 ÷ 0.8 = 342 Wh.
The 20% reserve and 80% usable fraction are illustrative assumptions, not universal specifications. Output mode, inverter consumption, temperature, battery condition and operating limits affect the result. Prefer relevant manufacturer runtime information and a practical test over treating the assumed fraction as guaranteed.
Check the output specifications separately
Compare the total load operating at one time with continuous output. For a motor or compressor, check startup compatibility with the appliance and station manufacturers. Jackery’s refrigerator guidance specifically distinguishes compressor startup demand from running power. Do not rely on a surge label without confirming the applicable conditions.
Confirm port types, cable compatibility, combined port limits and the intended AC or DC operating mode. A USB-C label alone does not establish that a laptop can receive its required charging profile.
Check the replenishment plan
Identify the actual charging source available during the outage. A solar input rating is an input limit, not a promise of that energy every hour. Estimate the available charging period and conditions, then test the equipment according to its instructions.
Record the tested result
Save the load list, output mode, starting charge, duration and result. If the tested duration falls short, reduce the load or change capacity and replenishment; do not simply add another unmeasured appliance.
Before sizing a battery, compare the operating constraints in generator versus power station. For cycling appliances, use the refrigerator guide. For work continuity, use the home-office plan.