What Size Power Station Do I Need? (UK 2026)

By Rob Hammond · Updated September 2026 · How we score

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Sizing a power station is not one number, it is three: the watt-hours it stores, the watts it can deliver continuously, and the surge watts it can deliver for a second or two when a motor starts. A unit that fails any one of the three is the wrong unit, and the commonest mistake, buying on watt-hours alone, is what leaves people with a 1kWh box that cannot boil a kettle. Everything below is computed with the same library that runs our power station sizing calculator, so the two agree.

The three checks, exactly as the calculator applies them

Our sizing library (src/lib/sizing.ts) does this and nothing cleverer:

1. Energy. It adds up watts × quantity × hours for everything on your list, then multiplies by 1.15. That 15% is a fixed allowance for inverter and conversion losses. The library calls it LOSS_FACTOR and it is 0.15. So a 1,050Wh load becomes a 1,208Wh requirement.
2. Continuous output. It adds up watts × quantity for everything at once, the peak, and requires the unit’s rated AC output to meet or beat it. No margin is added here.
3. Surge. It adds up each appliance’s start-up surge where one is defined and its running wattage where one isn’t, and requires the unit’s surge rating to cover the total. Where a product has no published surge figure, the library falls back to its continuous output, which is the conservative reading.

A unit “fits” only if all three pass. Runtime is worked out separately: usable energy is capacity × (1 − 0.15), divided by your peak watts. That assumes everything runs simultaneously and continuously, so treat the runtime figures below as a floor.

Step 1: what you want to run, and what it draws

These are the figures our calculator uses. Most are typical values, not measurements of your appliance, so check your own label or manual, because the spread within a category is wide. Where a manufacturer publishes a comparable number we’ve put it alongside.

Two of those deserve a caveat.

The fridge is deliberately pessimistic. Bosch’s product fiche for the KGN39VL3AG fridge-freezer gives 273 kWh/annum, which averages 31W across the year. Our 150W is the compressor’s draw while it is running, and a fridge compressor cycles. Multiplying 150W by six hours assumes it never stops, so the energy figure is a worst case, and deliberately so, because you would rather have headroom than a warm freezer. The 600W surge is the number that actually decides which units pass.

The kettle is at the bottom of the UK range. Russell Hobbs’ own listings run from 2,400W on the Honeycomb to 3,000W on the Calm. Our calculator’s 2,000W kettle is therefore the most generous assumption you could make about a British kitchen, and if yours is a 3kW model every “just passes” result below turns into a fail.

Step 2: does the output cover your biggest load?

This is the check that eliminates most units, and it has nothing to do with capacity. Take the 2,000W kettle against four real catalogue units, with the manufacturers’ own figures:

A boost mode is not the same as rated output. EcoFlow’s X-Boost and Bluetti’s Power Lifting both work by lowering the voltage delivered to the appliance, which is fine for a resistive load like a kettle or a heater and unsuitable for anything with electronics that expect 230V. EcoFlow states the DELTA 3’s X-Boost ceiling as 2,400W against a rated 1,800W; Bluetti gives the AC70 1,000W rated and 2,000W lifting. Our calculator ignores both and sizes on the rated figure, because that is the number the manufacturer stands behind. If you intend to rely on a boost mode, read its restrictions on the product page first.

The surge check, worked. Give a fridge its 600W start-up, add a 15W router and two 15W phone chargers, and the surge total is 645W. The DELTA 3 publishes no surge_w figure in our catalogue, so the library tests 645W against its 1,800W continuous rating, and it passes. The AC70’s 1,000W also covers 645W. So surge is rarely what stops a mid-size unit; capacity usually is, which is the next step.

Step 3: sizing the capacity

Three scenarios, each run through computeLoad and then through the catalogue with productFits. The arithmetic is shown so you can swap your own hours in.

Camping weekend, one day. Two phone charges (15W, 2h each), a laptop (70W, 4h), LED lights (40W, 5h) and a router (15W, 8h):

• 60 + 280 + 200 + 120 = 660Wh, ×1.15 = 759Wh required
• Peak (everything at once): 155W. Surge: 155W.

Six-hour power cut, essentials. Fridge (150W, 6h), router (15W, 6h), two phone charges (15W, 2h each):

• 900 + 90 + 60 = 1,050Wh, ×1.15 = 1,208Wh required
• Peak: 195W. Surge: 645W.

Twenty-four-hour cut. Fridge (150W, 24h), router (15W, 24h), LED lights (40W, 6h), two phone charges, a laptop (70W, 4h):

• 3,600 + 360 + 240 + 60 + 280 = 4,540Wh, ×1.15 = 5,221Wh required
• Peak: 305W. Surge: 755W.

Now the catalogue, at indicative catalogue estimates for price:

Three things fall out of that table.

The 1kWh class is a camping size, not a power-cut size. The DELTA 3 and the Anker SOLIX C1000 Gen 2 both hold 1,024Wh and both fail the six-hour fridge scenario: not on output, not on surge, but by 184Wh of capacity. A day’s camping is comfortably within them; six hours of fridge is not.

Runtime and scenario hours are different questions. The DELTA 3 shows 4.5 hours of runtime against the six-hour load, because runtime assumes every appliance runs flat out. It is under the six hours either way, which is why it doesn’t fit, but don’t read a runtime figure as a prediction of how long your fridge will stay cold.

Twenty-four hours is a big, expensive number. Only the DELTA Pro Ultra covers it on a single unit, at £4,299. If that is genuinely your requirement, read the last section before you buy.

Put your own appliances and hours in on the power station sizing calculator, which filters the whole catalogue on all three checks and shows an estimated runtime for each unit that passes. It’s linked rather than embedded here because it needs the catalogue’s product list to filter against.

Quick guidance by use case

• Phones, laptop and lights for a weekend. 750Wh and up. The Bluetti AC70 (768Wh, 1,000W, 10.2kg) clears the 759Wh camping load by nine watt-hours, which is fine, but leave yourself room if your hours run longer.
• A day off-grid with a fridge or power tools. 1kWh and ~1,800–2,000W. The EcoFlow DELTA 3 (1,024Wh, 1,800W, 12.1kg) or the Anker SOLIX C1000 Gen 2 (1,024Wh, 2,000W, 11.3kg), and the Anker is the one that reaches a 2,000W kettle.
• A power cut with the fridge running. ~2kWh. The Bluetti Elite 200 V2 (2,073.6Wh, 2,600W) is the smallest unit in our catalogue that passes the six-hour scenario.
• Longer cuts, or a heat-pump-adjacent load. 4kWh+ and expandable. The EcoFlow DELTA Pro 3 (4,096Wh, 4,000W, surge 8,000W) takes two extra batteries; the DELTA Pro Ultra is the only single unit here that covers a full day of essentials.

The full field is on our power stations hub, broken down into portable power stations and home-backup power stations, with our rankings at best portable power stations and best home-backup power stations.

Don’t over-buy, and when the answer is no

Weight is a spec. The AC70 is 10.2kg and the C1000 Gen 2 is 11.3kg, both a one-handed carry. The DELTA Pro 3 is 51.5kg and the DELTA Pro Ultra is 82.4kg. Those are not portable in any useful sense; they are appliances you install somewhere and leave. A 768Wh unit you actually take camping beats a 4kWh one that lives in the garage.

If your cuts are frequent and long, a power station is the wrong product. Ofgem’s guaranteed standards require network operators to restore supply within 12 hours outside severe weather, 24 hours in a category 1 storm and 48 hours in a category 2 storm. We can’t find an official published figure for how long a typical British power cut actually lasts, so we are not going to invent one, but those regulatory limits are the shape of the problem, and a 24-hour scenario needs £4,299 of power station. If you lose supply often, a home battery with a backup gateway does the same job automatically, at whole-house scale, and earns money the rest of the year by shifting cheap overnight electricity. Our are solar batteries worth it? guide works that arithmetic through, including the cases where it fails, and how much battery storage do I need sizes one.

Check you can refill it between cuts. EcoFlow states the DELTA 3 charges 0–80% in 45 minutes and 0–100% in 60 minutes; Bluetti gives the AC70 0–80% in 45 minutes at up to 950W; Anker gives the C1000 Gen 2 a full charge in 49 minutes at 1,600W input. All three are fast enough to be topped up in a lull. If you are sizing for a series of cuts rather than one, the recharge figure matters as much as the capacity.

You may not need to power the fridge at all. Bosch quotes a 16-hour temperature rise time for that KGN39VL3AG: the time a full freezer stays safe with the door shut and no power. Leave it closed and a short cut costs you nothing, which takes the single largest load off your list and can drop you a whole size class.

All prices, rates and figures were checked on 21 September 2026. Manufacturer specifications change between model revisions, so re-check the product page before committing.

What’s changed (changelog)

• 21 September 2026. Rebuilt on the catalogue and the sizing library. Every wattage, capacity, runtime and fit verdict is now either a manufacturer figure or computed with computeLoad / productFits / estimateRuntimeHours, replacing the round numbers the previous version used; added the surge check, the boost-mode caveat, the appliance table with manufacturer comparisons, and the section on when a power station is the wrong answer.
• 21 September 2026. Linked the sizing steps to the calculator that implements them (capacity, continuous output and surge are all checked, not just watt-hours).

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