Reference
Surge Watts and Continuous Watts
Every inverter has two wattage numbers, and the smaller one is the one that matters for most of the day. The larger one is the one that decides whether a motor ever gets going at all. Confusing them is the most common reason a battery that looks big enough shuts off with an error.
The two numbers on the box
Continuous wattage is what the inverter will supply indefinitely. Surge wattage, sometimes called peak, is a higher figure the inverter will supply for a very short interval before it protects itself and shuts down. Listings quote both, sometimes only the flattering one.
On the units in this catalog, the smallest pack states figures like 100 W continuous with 200 W peak. The larger ones state 1500 W and 1800 W outputs. Where a listing does not state a continuous figure, this site records it as not stated rather than inferring one.
| Unit | Continuous, as stated | Peak or surge, as stated |
|---|---|---|
| EcoFlow Delta 2, 1024 Wh | 1800 W AC output | Not stated on the listing |
| Jackery Explorer 1000 v2, 1070 Wh | 1500 W output | Not stated on the listing |
| Anker SOLIX C300, 288 Wh | 300 W output | Not stated on the listing |
| Jackery Explorer 300, 292 Wh | Not stated on the listing | Not stated on the listing |
| DARAN Power Station, 89.6 Wh | 100 W continuous | 200 W peak |
Why motors are the problem
A motor at rest has to be dragged up to speed against its own inertia and against whatever it is connected to. For that first fraction of a second it behaves close to a short circuit, and the current it pulls can be several times its running current. Compressors and pumps are the worst offenders because they often start against a load already sitting on them.
An inverter sees that spike as an overload. Well-behaved units ride out a brief surge within their peak rating and then settle. Units that cannot will cut the output and show a fault, which from the outside looks like the battery refusing to work at all.
The practical consequence: a pump with a modest running wattage can be entirely beyond a power station whose continuous rating comfortably exceeds that running wattage. The starting demand is what decides, and the starting demand is not on the front of the box.
- Resistive loads such as lights, phone chargers, and laptops draw essentially the same at switch-on as they do a minute later. They are easy.
- Motor loads such as fridges, freezers, sump pumps, and box fans have a starting demand well above their running demand.
- The starting demand is short, which is why peak ratings exist, but it is real and an inverter either supplies it or faults.
- Where a device page on this site marks a load as having surge, that is the reason.
Duty cycle pulls in the other direction
Surge makes motor loads harder than the label suggests. Duty cycle makes them easier. A fridge compressor does not run continuously; it runs until the box is cold, stops, and starts again when the box warms. Over an hour, the average draw is a fraction of the running wattage.
Both effects apply at once and they do not cancel out. Surge decides whether the load can start at all. Duty cycle decides how long the battery lasts once it has. This is why the device pages on this site quote a running wattage, a duty share, and an hour estimate built from the two.
Reading a spec sheet without being misled
A few habits make the comparison honest.
- Compare continuous ratings against continuous ratings. A peak figure next to a rival's continuous figure is not a comparison.
- The nameplate on the appliance, usually a sticker on the back or inside the door, is a better source than any general figure, including the ones on this site.
- Nameplate wattage on an appliance is a maximum, not a typical reading. Real running draw is often lower.
- If the listing does not state a continuous wattage, treat it as unknown rather than assuming the peak figure minus a bit.
- Watch how many things are running at once. Two loads that each fit can exceed the continuous rating together.