Backup Power

What Size Portable Power Station Do I Need?

By Global Cry Editorial · 19 August 2026

You do not need to guess what size portable power station to buy. A basic calculation gets you surprisingly close.

Step 1: list what you actually want to run

Do not start with the battery. Start with the devices. For a short power cut, that list might include:

Wi-Fi router
two mobile phones
laptop
LED lamp
radio

A completely different household might need specialist medical or accessibility equipment. In that case, check the exact electrical requirements and do not rely solely on a generic online calculator.

Step 2: find each device’s wattage

Look at the label on the appliance or its power adaptor. The number you need is watts (W). If only volts and amps are shown, the rough DC calculation is volts × amps = watts.

Step 3: multiply watts by hours

If a router uses 12W and you want it running for 10 hours, that is roughly 120Wh of energy. A 60W laptop used for three hours would be another 180Wh.

Add the energy requirements together to get an estimate.

Step 4: allow for losses

You will not get every advertised watt-hour out of a power station at the AC socket. The inverter and other electronics consume energy. For rough planning, add a margin rather than sizing the battery to the exact theoretical number.

A simple example

Router: 12W × 10h = 120Wh
Laptop: 60W × 3h = 180Wh
LED light: 8W × 6h = 48Wh
Phones and small devices: allow 50Wh

The theoretical total is 398Wh. A 400Wh power station would therefore be too tight once conversion losses and reserve capacity are considered. A unit in the 500–700Wh range would provide more breathing room.

Capacity is only half the equation

You must also check continuous output. A 1,000Wh battery with a 600W inverter cannot normally run a 1,200W kettle. High-power heating appliances are particularly demanding.

Starting surges

Some motors and compressors briefly draw more power when starting than they use continuously. Fridges, pumps and certain tools can therefore require a power station with enough surge capability even if their normal running wattage looks modest.

Common capacity bands

Under 300Wh

Good for phones, a router, lights and a laptop for limited periods. Lightweight and easy to carry.

300–700Wh

A useful middle ground for communications, computing and small household loads.

Around 1kWh

Much more flexible for home backup. Current examples in this class include the Jackery Explorer 1000 v2 at 1,070Wh and EcoFlow DELTA 3 Plus at 1,024Wh.

2kWh and above

Suitable when you genuinely need longer runtime or larger appliances, but cost, size and weight rise quickly. Expansion batteries can make sense if you want to grow a system later.

Do the calculation before buying solar panels

Solar input can extend runtime, but UK weather and panel placement vary. Treat solar as a way to replenish the battery, not an excuse to buy an undersized battery for a critical load.

Our rule

Calculate the energy you need, add sensible headroom, and then choose a unit whose continuous output comfortably handles the largest device you intend to run.

Safety note: follow the power-station manufacturer’s operating instructions, ventilation requirements and temperature limits. Never improvise connections to a home’s fixed wiring.

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