What Size Power Station Do I Need?
Updated October 2026Short version: work out the total watts your devices draw, then multiply by the hours you’ll run them to get watt-hours (Wh), and add a 20 to 30% buffer for real-world losses. For day trips, 200-500Wh is plenty. For weekend camping, aim for 500-1,000Wh. For home backup or van life, look at 1,000Wh and up.
That’s the whole method in one paragraph, but the detail matters, because two numbers get confused constantly: watts (how much power something draws right now) and watt-hours (how much energy is stored). Get either one wrong and you’ll either buy more battery than you need or find out mid-holiday that your fridge won’t switch on.
This page walks through both numbers, the appliance spike that catches most first-time buyers out, and a simple three-step method you can run on the back of an envelope. If you’d rather skip the maths, our sizing calculator does it for you.
What's the difference between watts and watt-hours?
Watts measure the rate of power draw at any given moment; watt-hours measure the total energy stored or used over time. A power station has to clear both hurdles: its continuous output (in watts) must be higher than whatever you plug in, and its capacity (in Wh) must be big enough to last as long as you need.
Think of watts as the width of a pipe and watt-hours as the size of the tank. A 60W laptop charger running for four hours uses 60 x 4 = 240Wh. Run that same laptop for a full working day (eight hours) and you’d need roughly 480Wh, before any buffer. A 100W camping fridge left on overnight (say, 10 hours) will pull about 1,000Wh, which is why fridges are usually what pushes buyers from a small unit into a medium one.
If a device label only shows volts and amps rather than watts, the sum is simple: watts = volts x amps. A 230V UK appliance drawing 2 amps is using roughly 460W.
What are surge (starting) watts?
Surge watts, also called starting watts, are the brief spike in power that motors and heating elements demand for a fraction of a second when they switch on. Anything with a compressor or motor (fridges, pumps, drills) can pull two to three times its running watts on start-up, and the power station’s inverter must handle that peak.
Most sizing guides stop at running watts and miss this number, which is the one that actually catches people out. This behaviour is known as inrush current. The appliance spikes hard on start-up, then settles down to its normal running figure.
A camping fridge that runs at around 60-100W can briefly demand two to three times that when the compressor kicks in. Which?’s generator buying guide notes that appliances with an induction motor, fridges and drills included, have a starting wattage around three times their running wattage. If your power station’s peak (surge) output can’t cover that spike, the inverter won’t let the appliance start at all, even though the running watts looked fine on paper.
The fix is straightforward: check the surge rating on a power station’s spec sheet, not just the continuous output, before you buy for anything with a compressor or a motor. It’s one of the most common reasons people write off a unit as “not powerful enough” when it was simply under-specified for that one split-second spike.
How do I work out the size I need?
Add up the running watts of everything you’ll use at once, multiply each device by the hours you’ll run it to get watt-hours, then add a 20 to 30% buffer for inverter losses. Real-world efficiency sits around 85%, so a 1,000Wh device total points you towards a 1,200-1,300Wh power station.
- Add up the running watts of everything you’ll use at once. Check appliance labels or manuals; if only volts and amps are listed, multiply them to get watts.
- Multiply by the hours you’ll use each device to get watt-hours. A 15W light run for six hours is 90Wh. Add up every device you expect to run in a day for your total daily Wh requirement.
- Add a 20 to 30% buffer for inverter losses. Some stored energy is lost converting battery DC power into 230V AC, so round up rather than down, especially for anything with a compressor where surge headroom matters most.
Worked example. A weekend camping setup: a 45W camping fridge running for 12 hours (540Wh), 10W of lights for 5 hours (50Wh), plus charging a phone and laptop (about 150Wh). That’s roughly 740Wh a day. Add a 25% buffer and you’re at about 925Wh, so a 1,000Wh model is the sensible pick.
What size power station do I need? (capacity tiers)
As a quick guide: 200-500Wh suits day trips and device charging, 500-1,000Wh covers weekend camping, 1,000-2,000Wh handles campervans and small home backup, and 2,000Wh-plus is for off-grid living and whole-property backup. Match the tier to your longest realistic session, not your shortest.
| Capacity | Best for | Example devices |
|---|---|---|
| 200-500Wh | Day trips, quick top-ups, emergency phone charging | Smartphones, tablets, a laptop, small LED lights |
| 500-1,000Wh | Weekend camping, short outages | Camping fridge, lights, a 32in TV, CPAP for a night or two |
| 1,000-2,000Wh | Longer camping trips, campervans, small home backup | Fridge-freezer, laptop and TV together, router, multiple lights |
| 2,000Wh+ | Off-grid living, whole-property backup, power tools | Larger fridge-freezer, power tools, several appliances at once, extended outages |
How many watts do common UK appliances use?
Small electronics (phones, laptops, routers, LED lights) draw under 100W and run for ages on a modest battery. The limiters are heating appliances: a kettle pulls around 2,800-3,000W and a fan heater about 2,000W, more than most portable units can deliver at all.
| Appliance | Running watts | Surge watts |
|---|---|---|
| Smartphone | 5-20W | n/a |
| Laptop | 45-65W | n/a |
| LED light (single) | 5-10W | n/a |
| Wi-Fi router | 10-20W | n/a |
| 32in TV | 40-80W | n/a |
| CPAP machine | 30-60W | n/a |
| Mini/camping fridge | 60-100W | 150-250W |
| Fridge-freezer | 100-200W | 400-600W |
| Electric blanket | 100-150W | n/a |
| Microwave | 800-1,200W | 1,200-1,500W |
| Coffee maker | 1,000-1,500W | n/a |
| Kettle | 2,800-3,000W | n/a |
| Fan heater | 2,000W | n/a |
| Power drill | 500-800W | 1,000-1,500W |
Figures are typical UK ranges based on manufacturer specs and Energy Saving Trust’s home appliance data rather than exact for every model, so check the rating plate on your own appliance where it matters. Either way, a kettle or a fan heater will exceed the continuous output of most portable power stations under about 2,000W, so treat those as the limiting factor when you size up, not the fridge.
Watch the kettle. Energy Saving Trust puts a typical kettle boil at around 3,000W, which trips up more buyers than almost anything else on this list.
What size do I need for camping, home backup or a fridge?
Match the capacity to the job: 200-500Wh for day trips, 500-1,000Wh for weekend camping, 1,000-2,000Wh for campervans and home backup, and 300-500Wh is often enough for a CPAP overnight. A fridge needs headroom for its start-up surge on top of its running watts.
Day trips and device charging: topping up phones, a camera and maybe a laptop between activities. 200-500Wh covers most of a day without mains power at all.
Weekend camping: lights, a camping fridge and some device charging over two or three nights points to 500-1,000Wh. Our best power stations for camping picks are built around this bracket.
Campervan and van life: running a fridge-freezer continuously alongside lights, a laptop and charging, day after day, needs 1,000-2,000Wh as a baseline, more if you’re off-grid for long stretches without solar top-up. See our campervan power station picks for models suited to permanent installs.
Home backup during a power cut: enough to keep a fridge-freezer, some lighting, a router and phone charging running through a typical UK outage sits at 1,000-2,000Wh, climbing towards 2,000Wh+ for more circuits or a longer cut. Our home backup power station guide breaks this down by household size.
Running a CPAP overnight: most CPAP machines draw only 30-60W, so an eight-hour night uses roughly 240-480Wh before buffer. A 300-500Wh unit is often enough on its own, though many buyers choose 500-1,000Wh so the same unit doubles up for other uses.
Frequently Asked Questions
It depends on what you’re running and for how long. As a rule of thumb, 200-500Wh suits day trips and device charging, 500-1,000Wh suits weekend camping, and 1,000Wh or more suits campervans, longer trips and home backup. Add up your devices’ watt-hours and add a 20 to 30% buffer to land on an exact figure.
A 1,000Wh power station can typically run a camping fridge for most of a day, charge a laptop and phone repeatedly, power LED lighting for several evenings, or keep a router and TV running for a few hours, depending on how many devices you use at once. Our related guide on what a 1,000Wh unit can run covers combinations in more detail.
That depends on what’s plugged in, because 2,000W describes the maximum power it can output, not how long it lasts. A 2,000Wh power station running a 100W load (a fridge, say) would last roughly 17 hours at around 85% real-world efficiency, but running a 2,000W heater would drain it in under an hour.
A mini or camping fridge running at 60-100W needs at least 500Wh to last a full day and night, with headroom for the compressor’s surge on start-up. A full-size fridge-freezer, which runs at 100-200W but can surge to 400-600W, is better matched to a 1,000Wh or larger power station with a solid surge rating.
For a weekend of camping with lights, a fridge and some charging, 500-1,000Wh is the usual sweet spot. Longer trips, or camping with a fridge-freezer and more devices running at once, push that towards 1,000-2,000Wh. Our camping picks are grouped by roughly this range.
A portable power station can back up specific circuits or key appliances such as a fridge-freezer, lighting, a router and device charging during a cut, but it won’t replace a whole-house supply the way a fixed home battery or standby generator can. For genuine whole-property backup you’re looking at 2,000Wh and up, often with solar input, and still choosing which appliances to prioritise rather than running everything at once.
Once you’ve settled on a rough capacity, browse our best portable power stations roundup or head straight to individual power station reviews to compare models within your bracket. If you’re planning to top up off-grid, our guide to solar charging covers panel sizing too.
Let us do the sums for you
If you'd rather not add anything up by hand, our free sizing calculator does the watts-to-Wh maths for you, buffer included, based on the devices and hours you enter. Not sure which category you fall into? The finder quiz asks a few quick questions and narrows down a sensible range before you start comparing models.
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