What is surge power, and when does it matter?

By the Ferncharge team · Figures last checked 21 October 2026

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The short answer: surge (or peak) power is the brief extra output a power station can give for a moment, above its continuous rating. It matters for appliances with a motor or compressor, such as fridges and freezers, which draw much more for an instant when they start. BLUETTI's manual says such devices may start at 2–4 times their rated power (BLUETTI manual).

Compared on manufacturers' published specs. Ferncharge has not tested these products. Estimates only.

Check your appliances' start-up in the runtime calculator: it adds the start-up watts and checks them against the power station's surge rating.

Continuous vs surge

• Continuous output is the most a power station's mains sockets supply at once, for as long as the battery lasts. Your appliances' running watts must fit inside it.
• Surge output is a short peak for start-up spikes. It isn't a figure to run anything at.

Stated figures (alphabetical, from makers' UK pages and manuals):

This compares stated figures only. Check the manual for your model.

Surge is not the same as a boost mode

Some figures in the table are boost modes for heating appliances such as kettles and hairdryers, not start-up surge ratings. Anker says SurgePad delivers the power station's rated power to a higher-wattage device (Anker UK user guide). A boost mode doesn't make a fridge's start-up spike any easier, and a surge rating doesn't let you run a 2,000 W heater. Read how each maker describes its figure.

How big is a start-up spike?

• BLUETTI: devices with motors or compressors may start at 2–4 times their rated power (BLUETTI manual).
• EcoFlow: a fridge's start-up surge is typically 2–3 times its running watts (EcoFlow).

For heating appliances such as kettles, the challenge is usually the high running wattage, which is what the makers' boost modes are described for.

How to add it up

A generator wattage worksheet gives a simple method: add up the running watts of everything that will be on, then add the single highest extra start-up (start-up watts minus running watts), because appliances rarely start at exactly the same moment (wattage worksheet, archived). Our calculators use the same method.

Example (our arithmetic): a fridge-freezer rated at 400 W, using BLUETTI's cautious 4×, could start at about 1,600 W. That's an extra 1,200 W. With a 10 W router and three 8 W lamps also on (34 W running):

• Running: 400 + 34 = 434 W: inside every continuous rating above except EcoFlow's 300 W.
• Peak: 434 + 1,200 = 1,634 W: inside the surge figures for BLUETTI (2,700 W) and Jackery (3,000 W).

Illustrative figures. Use your appliance's rating plate, and check the manual for how your power station handles start-up.

If several motor appliances might start together, add all their extra start-ups, not just the largest.

FAQs

What is surge power on a power station?

A brief peak output above the continuous rating, for appliances that draw extra power for a moment as they start.

Do I need to worry about surge for a kettle?

Not for start-up. A kettle's challenge is its high running watts, which must fit within the continuous rating, or a boost mode the maker says suits heating devices.

How much surge does a fridge need?

BLUETTI says motors or compressors may start at 2–4 times their rated power; EcoFlow says a fridge's start-up is typically 2–3 times its running watts.

Is a boost mode the same as surge?

No. Boost modes are for heating devices above the continuous rating; surge is a short start-up peak. Check how your maker describes each figure.

Related: Runtime calculator · Freezer · Hairdryer · Spec table