How do I calculate what size portable power station I need?

List the devices you want to run, find the wattage of each device, multiply watts by hours of use, then add the totals together. After that, add a reserve or efficiency buffer. For example, 500Wh of estimated use usually means you should look for a power station larger than 500Wh, often around 600Wh to 700Wh or more.

What size portable power station do I need for camping?

For light camping with phones, laptops, lights, and a small fan, a 300Wh to 700Wh power station may be enough. For a camping fridge, CPAP machine, Starlink, or several days off-grid, a 1000Wh to 2000Wh power station is usually more practical.

What size portable power station do I need for a refrigerator?

Many refrigerator backup setups need a mid-size or large power station, often around 1500Wh to 3000Wh depending on how long you want backup power. You also need to check the refrigerator’s startup surge, because compressor appliances can briefly require much more power when they turn on.

What size portable power station do I need for a CPAP machine?

The right size depends on your CPAP model, pressure settings, humidifier use, heated tube, and how many nights of backup you need. Many CPAP users should start by estimating overnight watt-hours and then choosing a power station with extra reserve. Always check your CPAP manufacturer’s power guidance before relying on a backup setup.

Is a 1000Wh power station enough?

A 1000Wh power station is enough for many camping, router backup, laptop, light, fan, and short CPAP use cases. It can also help with short refrigerator backup, depending on the fridge and runtime goal. It is usually not enough for long outages, heavy cooking appliances, heaters, or whole-home backup.

What is the difference between watts and watt-hours?

Watts measure how much power a device uses at one time. Watt-hours measure how much energy a battery can store. A 100W device running for 5 hours uses about 500Wh. This is why both output wattage and battery capacity matter when choosing a portable power station.

Why does the calculator include battery reserve?

Battery reserve makes the recommendation more realistic. Portable power stations lose some energy through inverter conversion, battery protection, wiring, and normal operation. Keeping a reserve also helps avoid planning around a completely drained battery.

Portable Power Station Size Calculator: Find the Right Watts & Wh

Use this portable power station size calculator to estimate how much battery capacity you need for camping, blackouts, RV trips, CPAP use, work gear, or emergency backup power.

The basic idea is simple: your devices use watts, your power station stores watt-hours, and your runtime depends on how long you want those devices to run. This calculator helps turn that into a practical battery size recommendation, so you do not have to guess between a small 300Wh unit, a mid-size 1000Wh station, or a larger 2000Wh+ backup system.

How to Use This Calculator

Start by choosing your main use case. This gives the calculator a better starting point for the kind of devices you are likely to run.

Then add the devices you want to power. You can adjust the watts, quantity, hours per day, and number of days for each device. For example, a phone charger may only need 10W for a few hours, while a refrigerator, CPAP machine, laptop, fan, or router may need a very different battery size.

Finally, choose your battery reserve. A 20% reserve is a good default because real-world portable power station runtime is rarely perfect. Inverter losses, battery protection settings, temperature, and device startup surges can all reduce usable capacity.

The Simple Formula

A portable power station size estimate starts with this formula:

Device watts × hours used = watt-hours needed

For multiple devices:

Total watt-hours = all device watt-hours added together

For a more realistic estimate, include efficiency losses and battery reserve:

Recommended capacity = total watt-hours ÷ usable battery percentage

For example, if your devices need 800Wh and you want to keep a 20% reserve, you should look for a power station with roughly 1000Wh or more.

Quick Size Guide

Power Station Size	Best For	Not Ideal For
200Wh–500Wh	Phones, laptops, lights, routers, small fans, short trips	Fridges, heaters, microwaves, long outages
500Wh–1000Wh	Camping, CPAP, laptops, routers, lights, small appliance backup	Heavy kitchen appliances or multi-day home backup
1000Wh–2000Wh	RV use, refrigerator backup, longer camping trips, short outages	Whole-home backup or long high-watt loads
2000Wh–3000Wh	Fridges, sump pumps, RV loads, power tools, longer outages	Lightweight travel or backpack-style portability
3000Wh+	Home backup, large RV setups, off-grid use, high-demand appliances	Casual camping or small-device charging

What Size Portable Power Station Do You Need?

For basic camping, a smaller power station can be enough if you are only charging phones, laptops, LED lights, cameras, and a fan. In that case, a 300Wh to 700Wh unit may be realistic.

For CPAP overnight use, the right size depends heavily on your machine, pressure settings, heated humidifier, and heated tube. Many setups can work with a mid-size power station, but you should always check your CPAP power requirements and manufacturer guidance before relying on any backup battery.

For refrigerator backup, capacity and surge output both matter. The power station needs enough continuous output to run the fridge and enough surge capacity to handle compressor startup. Runtime also depends on how often the fridge cycles on and off.

For RV or van life, think beyond one device. Add your fridge, lights, router, fan, water pump, laptop, Starlink, and small appliances together. A 1000Wh unit may work for light use, while a 2000Wh to 3000Wh system is more realistic for longer trips or higher comfort.

Common Runtime Examples

Setup	Estimated Use	Practical Size Range
Phone, laptop, LED light	300Wh–500Wh per day	500Wh–700Wh
CPAP for one night	300Wh–600Wh depending on settings	500Wh–1000Wh
Router, modem, laptop, lights	500Wh–900Wh per day	700Wh–1200Wh
Camping fridge, lights, fan, devices	800Wh–1500Wh per day	1000Wh–2000Wh
Refrigerator backup	1000Wh–2000Wh+ depending on runtime	1500Wh–3000Wh
RV essentials	1500Wh–3000Wh+ per day	2000Wh–3000Wh+

These are only starting points. The calculator gives a better estimate because it uses your actual device list.

Do Not Choose by Battery Capacity Alone

Battery capacity tells you how long a power station can run your gear. Output wattage tells you what it can run in the first place.

For example, a 1000Wh power station may have enough stored energy for a small fridge, but it still needs enough AC output and surge capacity to start the compressor. The same applies to coffee makers, microwaves, kettles, heaters, power tools, and pumps.

Before buying, check three things:

Battery capacity in Wh — how much energy it stores
Continuous AC output in watts — what it can run steadily
Surge rating — whether it can handle startup spikes

Battery Reserve Matters

Planning to drain a battery from 100% to 0% is not ideal. A reserve gives you extra room for real-world losses, unexpected loads, cold weather, and devices that use more power than expected.

For most people, a 20% reserve is a good default. For emergency backup, CPAP use, or longer outages, a larger reserve can make sense.

Should You Add Solar Charging?

Solar charging can reduce the power station size you need, but only if you have enough sun and enough solar input.

A 100W panel is helpful for small units, but it is slow for a 1000Wh or 2000Wh station. For larger power stations, look for higher solar input and consider 200W, 400W, or more depending on your daily energy use.

Solar is most useful for: