For one cordless-tool battery charger connected to 120 V AC, the supplied planning value is 360 W (range 25–1,000 W). The engine reports starting demand as 360 W (range 25–1,000 W); it does not add a separate motor-like startup surge.

The broad range covers lower-draw chargers through higher-draw multi-bay rapid chargers. It is not a specification for every charger or a class-by-class rating table. Because the exact model and AC input rating are unknown, check the charger's label or manual before choosing generator capacity.

One-charger generator check

For the registered one-charger example, the result is 450 W running, 360 W starting.

Under this scenario's bound method, the engine divides the 360 W running value by 0.80 to obtain 450 W of recommended running capability. It uses the supplied 360 W starting value without adding a separate surge. This method belongs to the current scenario; it is not a universal generator-sizing rule.

For this planning example, running capacity is the larger requirement: 450 W running versus 360 W starting. The result does not confirm that a particular generator will operate a particular charger. It does not validate connector fit, voltage quality, waveform requirements, grounding, manufacturer approval, charging behavior, or capacity for unrelated loads running at the same time. It also does not apply to a 12 V DC charger or vehicle adapter.

Why charger wattage varies

The supplied planning data spans chargers drawing tens of watts through higher-draw multi-bay rapid chargers. The three publisher values represented in the binding are 25–100 W, 360 W, and 1,000 W. These figures explain the overall range, but they are not model-matched specifications and should not be treated as fixed ratings for single-bay, rapid, or multi-bay classes.

Actual demand can depend on charger design, charge mode, and the number of occupied bays. This page's registered calculation is limited to one charger and supports no quantity or mode overrides, so it cannot calculate the combined demand of several chargers.

For a multiple-charger plan, separate the chargers into two groups:

  • Must run together: Collect each charger's AC input rating and include all overlapping loads.
  • Can take turns: Schedule them so their demands do not overlap.

Taking turns can reduce simultaneous generator demand, although charging all batteries will take longer. Do not multiply the 360 W typical value unless that value is suitable for every charger in the plan.

Check the input rating on your charger

For a model-specific value, use the charger—not the battery—as your source:

  1. Find the charger label. Look on the back, underside, or near the power cord. If the label is difficult to read, check the manual using the exact model number.
  2. Find the AC input line. Look for wording such as “Input,” “AC input,” or “120 V AC.” Do not substitute the battery's DC voltage or amp-hour rating.
  3. Record watts if listed. A rating stated directly in W is the clearest input for a power-planning calculation.
  4. If only volts and amps are listed, keep both values. This page does not convert incomplete nameplate data into model-specific watts. AC equipment may require an apparent-power or conservative planning check.
  5. For a multi-bay charger, use the complete unit's input rating. Do not assume each bay draws the full charger rating or that all bays behave identically.

Unknown is not zero. Until you find the rating, the 25–1,000 W range remains a low-confidence planning range. If charging is essential during an outage, use the model-specific input and check the charger's requirements rather than relying on the 360 W typical value. Optional charging can instead be scheduled after higher-priority household loads finish.

Running watts are not daily energy

Watts measure power, which is the rate of using energy at a given moment. Watt-hours (Wh) and kilowatt-hours (kWh) measure energy over time.

This lookup supplies running power, but it does not supply charging duration, daily charging sessions, battery state of charge, duty cycle, battery capacity, or charger efficiency. We therefore cannot present the running-watt value as daily energy.

An energy calculation needs a supported power value and the time for which that power applies. Because the required time and operating pattern are absent, this page does not calculate Wh per charge, kWh per day, generator runtime, or charging time.

Choose the right planning path

For the simplest one-charger plan, find the charger's AC input rating. Then account for that load alongside the essential equipment that must remain powered. Also check the charger and generator documentation for any connection, power-quality, or other operating requirements this capacity calculation does not evaluate.

If several chargers must operate together, collect the AC input rating for each one and use the generator size calculator to plan the combined load. If they can take turns, create a charging schedule and include only the chargers that will overlap. Keep essential household loads separate from optional battery charging.

For more detail on generator power ratings, see Running Watts vs Starting Watts. These planning checks do not guarantee charger compatibility, successful charging, or generator runtime.