Free Tools to Size and Choose Your Power Station
Updated August 2026This portable power station calculator and its companion finder quiz cut out the guesswork. The calculator turns your appliance list into a watt-hour target in under a minute; the quiz asks five short questions and matches you to a shortlist of models. Both come from the same research and honesty as the rest of this site: real UK wattages, a 20% buffer for start-up surge, and no email address required to see your result.
We build both tools the way we write every review: from manufacturer spec sheets, hundreds of verified UK Amazon and Trustpilot reviews, and professional teardown research, rather than fake hands-on testing claims. The wattages and capacity bands below come from that same process.
Below, we show how the calculator’s maths works, list the five questions the quiz asks, and walk through a real camping scenario for one night away. There’s also a table of common UK appliance wattages, covering items the calculator does not list individually.
How does the portable power station calculator work?
The calculator multiplies each device’s watts by its hours of use to get watt-hours per day, totals your devices, then adds a 20% buffer for appliance start-up surge, then a separate 10% allowance for inverter losses.
Here’s the maths in full. A 60W cool box running for 4 hours a day uses 240 watt-hours; a 20W light for 5 hours adds 100Wh; two phone charges at 10W for 2 hours each add 40Wh; a 60W laptop for 3 hours adds 180Wh. Add it up and you get 560Wh a day before any buffer.
Why add a 20% buffer? Some appliances briefly draw more than their rated wattage on start-up. Fridge compressors are the classic case. That surge is what the 20% buffer covers.
Inverter losses are handled separately from the surge buffer. A power station’s rated capacity is measured at the cells, not at the socket, and some power is lost in conversion to 230V AC. Energy Saving Trust’s solar inverter efficiency data puts well-built fixed inverters at 93 to 96%, so a smaller power station inverter losing nearer 10% is a fair planning assumption. A battery labelled 750Wh therefore delivers closer to 675Wh at the socket, applied after the surge buffer.
How does the finder quiz work?
The quiz asks five short questions about how you’ll use a power station, then matches your answers to models we’ve reviewed. It takes under two minutes and gives you a shortlist rather than a single push toward one product, so you can compare before you decide.
1. What will you mainly use it for?
Camping or Festivals / Home Backup / Campervan or Van Life / Remote Work or Job Sites.
2. How much run-time do you need between charges?
A few hours / A full day / Multiple days off-grid.
3. What’s your budget bracket?
Under £250 / £250 to £500 / £500 to £1,000 / Over £1,000.
4. How important is solar charging to you?
A priority / Nice to have / Not fussed.
5. How much does portability matter?
Needs to be light and easy to carry / Weight isn’t an issue, it’ll mostly stay put.
The shortlist you get is built from the research behind our reviews: manufacturer specs, verified UK owner feedback on Amazon and Trustpilot, and professional teardown analysis.
Quiz results link to retailers, including Amazon. Some are affiliate links, and we may earn a commission at no extra cost to you. That never changes which model we recommend. Read our full affiliate disclosure.
A worked example: one night of camping
Maths is easier with a real scenario: a 12V cool box, LED camping lights, a couple of phone charges, and a laptop for some downtime once it gets dark.
| Device | Typical watts | Hours per day | Watt-hours per day |
|---|---|---|---|
| 12V cool box | 60W | 4 hrs | 240Wh |
| LED camping lights | 20W | 5 hrs | 100Wh |
| Phone charging (x2) | 10W | 4 hrs total | 40Wh |
| Laptop | 60W | 3 hrs | 180Wh |
| Total | 560Wh |
That’s 560Wh a day before the buffer. Add 20% for start-up surge and you land on 672Wh. Because roughly 10% of the rated capacity is lost in the inverter on the way to the socket, the unit you’d want to buy needs a rated capacity closer to 750Wh.
Look at 750Wh or more for a single night. For a two-night weekend, double the daily figure and aim for around 1,500Wh, which means shopping in the gap between the 1,000Wh and 2,000Wh bands.
What do common UK appliances draw in watts?
Wattage varies by brand and model, but these figures give a realistic starting point for UK 230V appliances. Kitchen items like kettles and toasters draw far more than most people expect, often over 1,000W, while laptops and routers draw comparatively little. The phone charger row includes modern fast chargers, which draw more than older 5W adaptors. Always check the rating plate on your own appliance before relying on these numbers.
| Appliance | Typical wattage |
|---|---|
| Kettle (rapid boil) | 2,200 to 3,000W |
| Microwave (800W cooking power) | 1,200 to 1,300W |
| Toaster (2-slice) | 900 to 1,200W |
| Electric drill (corded) | 500 to 750W |
| Fridge-freezer | 100 to 200W running, higher on start-up |
| Hairdryer | 1,200 to 2,000W |
| Iron | 1,000 to 2,400W |
| Slow cooker | 150 to 300W |
| Filter coffee machine | 800 to 1,200W |
| TV (32 to 50in LED) | 50 to 100W |
| Laptop | 45 to 65W |
| Phone charger | 10 to 45W |
| WiFi router | 10 to 20W |
| CPAP machine | 30 to 60W |
| 12V cool box | 40 to 60W |
| Angle grinder | 750 to 2,000W |
These are typical figures, not a substitute for checking the rating plate on your own appliance. Wattage is only half the story: the Energy Saving Trust’s breakdown of which appliances take the biggest share of a UK energy bill puts washing machines, dishwashers and tumble dryers top at 14%, because they run for long cycles. Actual draw varies by brand and age, and anything with a motor or compressor can spike well above these numbers on start-up.
What can each capacity band actually run?
Capacity bands give a rough guide before you check exact specs: around 300Wh for device charging, 600Wh for a light overnight with a cool box for part of the evening, 1,000Wh for a small fridge or basic home backup, and 2,000Wh-plus for multi-day, whole-appliance backup.
Around 300Wh
Enough to charge phones, tablets and a laptop several times over, or run LED lighting for a few evenings. Suits day trips and festivals, where charging devices matters more than running appliances. See our camping power station picks.
Around 600Wh
Covers a light single night: lighting, device charging and a few hours of cool box. The full worked example above needs more than this band delivers, so step up if you’re running a cool box all evening. It also covers short home backup, a router and some lighting through a brief cut. Our campervan power station guide covers models suited to this.
Around 1,000Wh
Stretches to a small fridge for the best part of a day, depending on how often the compressor cycles, a laptop for well over a day, or a CPAP machine overnight with charge to spare. This is where power stations start to double as home backup. See our home backup picks.
2,000Wh and above
This is the range for running a fridge-freezer through a multi-day cut, or keeping several rooms lit and devices charged during an extended outage. UK power cuts are rare: UK Power Networks, which covers London, the East and the South East, reports customers there see an interruption on average once every 32 months, but this band covers the longer ones properly. The EcoFlow Delta 2 Max is our pick for buyers who need this much headroom.
Where to go next
If you’d rather read than click through a calculator, our size guide covers the same sizing logic in plain English, with more UK use cases worked through. For a ranked shortlist of the models we’d actually buy, see our best portable power stations picks, or narrow it down by use case: camping, home backup, or campervans. To compare specific models side by side, the reviews hub has the full breakdowns.
Frequently Asked Questions
The calculator is only as accurate as the wattage and hours you enter: it’s a planning tool, not a lab measurement. We use realistic UK figures and a 20% buffer for start-up surge. For anything safety-critical, like medical equipment, check the manufacturer’s rating plate.
No. Both tools work instantly in your browser, no sign-up and no email required. You’ll see your watt-hour target or shortlist straight away.
Yes. Every wattage and the maths behind the calculator assume UK 230V mains and BS 1363 sockets, not the US 120V standard. Figures from an American site will show different wattages for the same appliance.
Some appliances briefly draw more than their rated wattage on start-up, and fridge compressors are the classic case. The 20% buffer covers that surge. Inverter losses are handled separately, as a 10% derate on the battery’s rated capacity.
It’s built for portable power stations covering key appliances during a cut: a fridge-freezer, some lighting, a router, not a whole-house system. Backup covering circuits like heating and hot water needs a proper electrician’s assessment instead.
Not directly. The calculator works out how much capacity you need; solar charging time depends on panel wattage, season and UK weather, which varies too much for one formula. Our solar charging guide covers realistic UK charging times.
Once you have a target capacity in mind, our best portable power stations page lines up the models we rate for UK conditions. These tools are updated as we add new models and refine the maths behind them.
Portable power station calculator or finder quiz: which should you use?
Reach for the sizing calculator if you already have a rough list of what you'll be running (a cool box, some lights, a laptop) and want a clear watt-hour target. Choose the finder quiz instead if you're starting from scratch and would rather answer a few quick questions than do the sums yourself.
Sizing Calculator
Takes about a minute. Turns your appliance list into a watt-hour target and a recommended capacity band.
Sizing Calculator
Finder Quiz
Five questions, under two minutes. Matches you to a shortlist based on how, and where, you'll use it.
Finder Quiz