Settle the Can-It-Run-It Question in One Sitting

Two failure modes, two different numbers

The start-up failure is dramatic. The station's screen flashes an overload warning, the compressor never turns over, and nothing else is wrong. It happens because surge demand crossed the surge rating, usually with refrigerators, pumps, compressors and some power tools.

The marathon failure is quieter. Everything starts fine, the lights stay on, and three hours later the station is empty because the runtime maths was never done. A device can pass the first test and lose the second every single evening.

Keeping the two apart saves money. A unit that trips on fridge start-up needs a higher surge rating, not a bigger battery. One that dies by lunch needs more capacity, not a beefier inverter. The checker above names which fix you actually need.

There is a third, softer failure worth knowing. Some stations survive both tests but throttle output when their housing heats up on a warm day. The runtime you calculated in a cool kitchen shrinks quietly in a hot garage in August.

• Surge events last a second or two. Continuous ratings last all day.
• Heaters and kettles have almost no surge, but enormous steady draw.
• Compressors invert that: gentle running watts, brutal start watts.

Worked example: the fridge on a 1,000 Wh station

Take the default pairing: a fridge averaging 120 W with a 700 W start surge. The station is rated 600 W continuous with a 1,200 W surge ceiling and 1,000 Wh stored. The start passes easily, 700 against 1,200. The steady run passes with room, 120 against 600.

The marathon number decides the night. Usable energy after 15% losses is 850 Wh, which at 120 W steady draw covers about seven hours of compressor duty time. Across a day of duty cycling that stretches to well over a full 24 hours, because the fridge is not running the whole time.

Now move one number. A 2,200 W kettle on the same station fails the continuous test outright. No stored energy in the world fixes that pairing, because the fight is lost at the inverter, not the battery. The verdict line says exactly that, so no one has to learn it at 2 a.m.

Notice the shape of that kettle result. It is the clearest example of the two gates disagreeing. The fridge has a large surge and a small continuous draw, so it leans on the surge rating. The kettle has no surge and a huge continuous draw, so it leans on the continuous rating. Same station, opposite problems, opposite fixes.

Finding your appliance's two numbers honestly

Running watts usually live on the label, but for cycling devices the label overstates reality. A fridge plate might read 200 W while the measured average sits near 100. Use the label for a safe upper answer, or a plug-in meter for the true one.

Surge is the figure brands quietly omit. A useful planning rule: multiply compressor running watts by three to seven. Small fridges tend toward the lower end, older units and freezers toward the top of the range.

Resistive devices need no surge study. Kettles, heaters, lamps and most electronics draw whatever the label says. They are at full power from the first second, so enter the same number twice and let the checker weigh only the steady fight.

When the answer is no, what actually fixes it

A failed surge test has exactly two honest fixes: a station with a higher surge rating, or removing the appliance from the backup list. Adapters, extension leads and hope do not change the inverter's reflex. Some brands offer a higher-surge firmware note on otherwise identical models, and that spec line is worth more than marketing watts.

A failed continuous test can sometimes be negotiated. Running the fridge at 120 W instead of the oven at 2,200 W is a load-shedding decision. The household outage planner pages here are built for making that call deliberately, rather than after the battery has already bottomed out.

A passed start but short runtime is a capacity or recharging conversation. Solar refill during the day, or swapping one hungry device for a lower-draw equivalent, moves the answer further than any setting on the station itself.

Accuracy, assumptions and limitations

The checker compares your entered numbers against each other. It cannot verify that your fridge's label reflects its real surge. It cannot confirm that the station's published surge rating holds as the battery ages. And it cannot tell whether cold is stealing a tenth of the stored energy in a garage.

Surge ratings are also the least standardised spec in the industry. Brands measure them differently, some quote them generously, and the real margin shows up in owner reports rather than datasheets. A pairing that passes with less than 30% headroom is a pairing worth reading reviews for.

Treat a clean yes as a licence to shop, not a guarantee of a marriage. The first real outage is the honest test. A station that starts the fridge warm on the bench may meet a frozen compressor with a much hungrier start-up one January night.

The checker also knows nothing about output mix. Some stations reserve one high-surge socket for exactly the kind of load that needs it, and the same device through a general outlet can behave differently. When the spec sheet splits those details, split your test plan too.