1 · Pick your devices
Tap + to add. Adjust watts and hours per day if you know them. AC = plugs into the inverter outlet, DC = USB or 12 V port.
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Energy per day–
Capacity to buy (min.)–
Continuous output (min.)–
Largest single device–
Runtime on recommended–
Solar covers–
Wall outlet (AC)–
Solar (your panels)–
Car 12 V socket–
Watt-hours vs. watts: the two numbers that matter
Every portable power station is described by two ratings. Capacity in watt-hours (Wh) is the size of the fuel tank – how much energy is stored. Output in watts (W) is the size of the engine – how much power it can deliver at one moment. A 1,000 Wh station can run a 100 W device for roughly 8 – 9 hours, but it cannot run a 1,500 W kettle at all if its inverter is rated at 800 W.
How the calculation works
For each device we multiply watts × hours per day × quantity. Devices on the AC outlet are divided by an inverter efficiency of 85 %, because converting battery DC to 120/230 V AC wastes energy as heat; USB and 12 V devices are divided by 95 %. The daily total is multiplied by the number of days between recharges and your safety reserve, then divided by 0.95 because a station's usable capacity is slightly less than its label. Output power is based on the devices you are likely to run together plus your biggest appliance.
Use real wattages, not charger labels
A laptop charger rated at 100 W usually draws 30 – 60 W. A 12 V compressor cooler rated at 45 W runs only a third to half of the time, which is why we default it to 8 hours of operation per 24. CPAP machines vary widely: 30 – 60 W without a heated humidifier, up to 90 – 110 W with one. Turning off the humidifier and using a DC adapter can double your CPAP runtime.
Power station size classes
| Capacity | Typical output | Weight | Best for |
|---|
| 200 – 300 Wh | 300 W | 3 – 4 kg | Phones, cameras, lights, a laptop – day trips |
| 500 – 700 Wh | 600 – 800 W | 6 – 8 kg | Weekend camping, CPAP for 1 – 2 nights, 12 V cooler |
| 1,000 – 1,500 Wh | 1,500 – 1,800 W | 11 – 17 kg | Van life, coffee maker, short blackout backup |
| 2,000 – 3,000 Wh | 2,200 – 3,600 W | 20 – 32 kg | Fridge + essentials during outages, power tools |
| 4,000 Wh + (expandable) | 3,600 – 7,200 W | 40 kg + | Whole-day home backup, 240 V appliances |
Battery chemistry: LiFePO4 vs. NMC
Most current power stations use lithium iron phosphate (LiFePO4 / LFP) cells rated for 3,000 – 4,000 cycles to 80 % capacity – that is ten years of regular use. Older and lighter designs use NMC cells, which are about 30 % lighter per Wh but typically rated for 500 – 1,000 cycles. If you will cycle the battery often (van life, daily solar), LiFePO4 is the better value; for occasional camping an NMC unit is fine.
Recharging: wall, car and solar
Wall charging speed varies enormously between models: some 1 kWh stations refill in under an hour, others take six. A car's 12 V socket usually supplies only 100 – 120 W, so it is a top-up rather than a full recharge. Solar output is approximately panel watts × peak sun hours × 0.75 to account for panel angle, heat and controller losses. If solar can cover your daily use, you can stay off-grid indefinitely – the calculator shows how close you are.
Features worth paying for
- Pure sine wave inverter – essential for CPAP, laptops and anything with a motor.
- Surge rating of at least 2× continuous for fridges and pumps.
- UPS / EPS mode with fast switchover (< 20 ms) if you'll use it as backup for a computer or medical device.
- Solar input voltage and wattage that match the panels you plan to buy (MPPT controller).
- USB-C PD ports at 100 W or more for laptops – charging via DC avoids inverter losses.
- Expansion battery support if your needs may grow.
- Pass-through charging and a low self-discharge rate for emergency storage.
Frequently asked questions
How long will a 1000 Wh power station run a refrigerator?
A modern full-size refrigerator uses about 1 – 2 kWh per day, so a 1,000 Wh station runs it for roughly 10 – 20 hours. You'll need at least 1,500 W of output with good surge capacity for the compressor start.
What size power station do I need for a CPAP?
Without a humidifier, a CPAP typically uses 30 – 60 W, or 250 – 450 Wh for an 8-hour night including inverter loss. A 500 Wh station covers one night with margin; 1,000 Wh covers two to three nights.
Can a power station run a microwave or kettle?
Only if its continuous output exceeds the appliance's input power – about 1,200 – 1,800 W for most microwaves and kettles. They use little energy because they run briefly, so a 1,000 Wh unit with 1,800 W output can handle them.
Power station or gas generator?
Power stations are silent, fume-free and safe indoors, but store limited energy. Generators provide continuous power as long as you have fuel. Many people pair a power station with solar panels for quiet everyday use and keep a generator for long outages.
Can I take a power station on a plane?
Airlines generally allow lithium batteries up to 100 Wh in cabin baggage, and up to 160 Wh with approval. Almost all power stations exceed these limits and cannot be flown.
About Packwatt
Packwatt is an independent, free calculator that works out how many watt-hours and output watts you need from a portable power station, and how quickly you can recharge it from the wall, a car or solar panels. We are not affiliated with any power station brand.
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The methodology combines widely published engineering rules of thumb, manufacturer data sheets and the electrical code practices that installers use every day. We review the assumptions regularly and update the calculator when typical product specifications change.
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