Startup planning · Reviewed September 12, 2026
Running watts describe normal operation; total starting watts describe the demand during a start. Additional starting watts are only the increase above running watts. Mixing the last two quantities can inflate a load estimate or hide a missing requirement.
Label the three quantities
Use P for running watts, S for total starting watts and ΔP for additional starting watts. When the figures describe the same operating scenario, ΔP = S − P. Before entering a manufacturer’s number, check which quantity it represents. If the document does not say, ask rather than guessing.
The Generac wattage worksheet, PDF page 25 adds running load and the largest additional starting demand. This explains the arithmetic; its example appliance values are not universal refrigerator ratings.
One refrigerator starting with other loads running
Illustrative inputs only: a refrigerator runs at 160 W, needs 640 W total during startup, and shares the source with a steady 30 W load.
Normal combined demand: 160 + 30 = 190 W.
Additional starting demand: 640 − 160 = 480 W.
One-start scenario: 190 + 480 = 670 W.
The direct check is 640 + 30 = 670 W. Adding 640 to 190 would count the refrigerator’s running portion twice.
What quantity changes
With two identical units using those illustrative figures, the running load would be 320 W before other devices. If one unit starts while the other runs, the scenario is 640 + 160 = 800 W. If both start together, it is 1,280 W. Quantity therefore affects both energy and possible overlap.
Backup Power Map V1 reports one physical unit starting and all listed units starting. These are scenarios, not predictions of compressor timing. A system that relies on staggered starts needs an actual operating arrangement that makes that assumption reliable.
Why watts alone cannot certify a start
Compare surge duration as well as magnitude. Current, VA limits, voltage behavior and battery discharge limits can also matter. Victron’s inverter selection guidance discusses continuous and startup capability. A large surge label without its duration does not establish how the unit handles your refrigerator.
If a label gives only amps, V × A is apparent power in VA. Do not silently rename that result real watts without the relevant power factor. Do not invent a fixed startup multiplier to fill the gap.
What to collect before comparing products
- The exact appliance model and starting method.
- Whether each figure is running, total starting or additional starting demand.
- The required duration and any current/VA information.
- Other loads that may overlap and the source’s conditions or derating.
Leave unknown startup inputs blank in the calculator. An unresolved result is more useful than a precise-looking number with no equipment basis.
Turn the record into a backup plan
Start with the refrigerator sizing guide, then use Backup Power Map. For an example of the evidence to check, see our EcoFlow DELTA 3 Plus US research profile. The manufacturer link there is an ordinary link that currently earns no commission; it is not a claim that this product fits your appliance.