Portable Power Station Size Calculator

What this portable power station calculator is for

This guide helps shoppers and homeowners estimate a realistic battery capacity before comparing a portable power station, solar generator, or backup battery for camping, RV travel, apartment outages, refrigerator support, router backup, laptop work, CPAP backup planning, fans, phones, cameras, and LED lighting. It is designed for early sizing decisions: you list the devices you expect to run, estimate how many watts each device draws, choose the number of hours you need it each day, and add a real-world reserve before looking at 300Wh, 500Wh, 1000Wh, 1500Wh, and 2000Wh-plus capacity classes.

The page is not a product ranking, a medical instruction page, or a promise that a battery will run your equipment. Power stations vary by usable watt-hours, inverter efficiency, continuous watts, surge watts, output ports, charging input, temperature limits, battery age, firmware behavior, and manufacturer safety restrictions. Treat the result as a planning range that must be checked against official device and product specifications.

Inputs used by the calculator

• Device watts: the running wattage from a nameplate, power meter, manufacturer manual, USB-C charger rating, or conservative estimate.
• Quantity: how many of that device will run at the same time or during the same day.
• Hours per day: expected daily use time, such as eight hours for a CPAP machine, six hours for a fan, or two hours for phone charging.
• Efficiency and reserve buffer: an added percentage for inverter loss, cold or hot weather, battery aging, device setting changes, and the risk of underestimating load.
• Optional solar offset: a rough daily recharge estimate from panels, used only after considering shade, sun angle, weather, controller limits, and cable loss.

Calculation logic and formulas

The base energy formula is watt-hours = watts × hours × quantity. A 65W laptop used for 4 hours is about 260Wh before losses. Two 12W phone chargers used for 2 hours are about 48Wh. A 45W CPAP machine used for 8 hours is about 360Wh before humidifier, heated tubing, adapter, and reserve assumptions.

After adding all devices, the calculator applies a buffer: required Wh = daily Wh × (1 + buffer percent ÷ 100). If you enter a solar recharge estimate, the tool subtracts it only as a planning offset: net daily Wh = buffered Wh − expected solar Wh, never below zero. The output is then mapped to a practical capacity band rather than a single exact product size because real usable capacity and inverter behavior differ by model.

Example planning scenarios

Weekend camping electronics

Two phones, a laptop, LED lights, and a small fan may land near a 500Wh class station if use is moderate. If cloudy weather, a powered cooler, camera charging, or multiple people are involved, a 1000Wh class station may be more comfortable.

Short apartment outage kit

A router, phones, LED lights, and one fan can often be planned separately from heavy cooking loads. A 300Wh to 500Wh class station may cover communications and light comfort for a limited period, while refrigerator support usually needs a larger capacity and surge check.

CPAP overnight backup planning

CPAP power use depends heavily on model, pressure, humidifier, heated tubing, and adapter type. Start with official manufacturer wattage or Wh-per-night guidance, add a reserve, test the setup before an outage, and keep redundant backup options. This site is educational only and is not medical advice.

Refrigerator or compressor load

Refrigerators are difficult because cycling, room temperature, age, door openings, defrost behavior, and startup surge change real use. A battery can have enough watt-hours but still fail if inverter surge or continuous watts are below the refrigerator requirement.

Capacity classes to compare

• 300Wh: small electronics, phones, cameras, and brief lighting use.
• 500Wh: stronger camping baseline for phones, laptops, LED lights, router backup, and a modest fan schedule.
• 1000Wh: common range for outage essentials, CPAP with careful verification, mini fridge support, or longer camping reserve.
• 1500Wh: more practical for refrigerator planning, longer outages, RV basics, or several comfort devices.
• 2000Wh+: larger home backup loads, multiple appliances, extended outages, or situations where separate batteries may be safer and more flexible.

Frequently asked questions

Can this calculator tell me exactly how long a power station will run?

No. It estimates a range. Actual runtime depends on usable battery capacity, inverter efficiency, load changes, temperature, battery age, and manufacturer limits.

Should I include high-watt appliances such as kettles, heaters, or coffee makers?

You may include them for awareness, but high-watt heat appliances drain batteries quickly and may exceed inverter limits. Check continuous watt and surge ratings before planning around them.

Is solar recharge guaranteed?

No. Solar input changes with weather, shade, panel angle, season, temperature, cable loss, panel rating, and charge controller limits. Use conservative solar numbers and keep a reserve.

Can I rely on this for CPAP backup?

Do not rely on this site as your only CPAP backup plan. Verify official CPAP requirements, use approved adapters, consult the manufacturer or equipment supplier, and plan redundant power for overnight dependence.

Why does the tool suggest a range instead of one product?

Because battery capacity, usable output, inverter limits, surge capacity, ports, recharge speed, weight, warranty, and safety limits differ between products even when the advertised watt-hours look similar.

Important limitations

All calculations are educational estimates. This website does not provide professional electrical, medical, engineering, safety, or purchasing advice. It does not guarantee compatibility, runtime, charging speed, solar performance, appliance startup, or safe operation. Before buying or relying on a battery setup, verify official device specifications, battery manufacturer instructions, cable ratings, local rules, ventilation and temperature limits, and your personal risk tolerance. The site currently has no live product links, no real affiliate links, no external tracking, and no contact collection.