ZDNET’s key takeaways
- A power station is much more than its capacity.
- Instead of calculating specs independently, you should consider them as a whole.
- Calculate how big a battery needs to be by considering its average power draw and runtime.
As someone who tests power stations for work, I have different sizes and capacities for different purposes. I use my small portable batteries for handheld devices or laptops, a medium one to power our router and modem to avoid internet interruptions, and the largest ones for whole-home backup.
Also: I recommend you don’t run these appliances on your power station – even if you can
While the right-sized power station isn’t all that hard to determine, many users still consult the big old internet for guidance on how to calculate one that fits their needs.
From everyday use to camping and home backup systems, I’ll break down how to calculate the right power station for you.
1. Identify your use case
Make a list of the devices you want to run on a power station. This starts by determining what you will power with your power station and what purpose it will serve.
Backup power
If you want your power station to keep essential devices running during a power outage, make a list of those devices and their typical power draw to determine the minimum capacity you’ll need. For example, I keep these devices on backup power:
- Refrigerator: 300W
- Wi-Fi modem and router: 20W
- Security system: 40W
- 3 ceiling fans: 300W
- 5 LED lights: 50W
- Phone and tablet chargers: 100W
- Sometimes/just in case: Microwave for quick meals, laptop chargers, pedestal fan: up to 1,500W
Total: 2,310W
Recommended size: at least 3kW
Some good options include the Bluetti Apex 300, EcoFlow Delta 3 Ultra, and Anker Solix F3000. I keep an EcoFlow Delta Pro Ultra X as my whole-home backup battery, which can handle all my essentials and the refrigerator’s surge.
Camping
A power station for camping trips doesn’t need to be as large as one for backup power. Still, you need to make a list of the items you plan to power during your camping trip so you’re not left without power when needed. Here’s an example list of what I power during camping trips:
- Phone chargers: 100W
- Multiple rechargeable lights and flashlights: 50W
- In-tent fan: 15W
- Inflatable mattress: Up to 200W (less when reinflating on multiple nights)
- Other: If you need a CPAP machine to sleep, consider your machine’s wattage as well
Total: 365W
Recommended size: 500W per night
Some good options include the EcoFlow River 3 Max, Jackery Explorer 1,000 v2, DJI Power 1,000 V2.
Travel/road trip
If you take a backseat full of kids on long road trips, chances are you keep certain devices charged to entertain them. Most newer vehicles feature multiple charging ports, but a portable battery can help in a pinch. Here are some examples of devices I may charge for my kids during road trips:
- Tablet chargers: 80W
- Phone chargers: 100W
- Headphones: 10W
Total: 190W
Recommended size: 300W
Some good options include the Anker Solix C300, EcoFlow Trail Plus, EcoFlow Trail 300.
Casual use
You probably don’t need a large capacity portable battery to casually charge devices like laptops, tablets, and phones. There are multiple portable power stations that work with these devices, such as the 165W Anker Laptop Power Bank and the 170W EcoFlow Laptop Power Bank.
2. Consider how much you need at once – and then some
Calculating how much you need involves adding up the wattage of every device you expect to run simultaneously, then adding some headroom. As you can see in the examples above, I added a bit of extra wattage to the recommended size in each category above the total calculated load. If you have a 380W load, then consider a power station with an output of at least 500W.
Also: The hidden metric that makes these portable power stations truly worth your money
You must also consider surge and startup wattage, which are factors for devices with compressors, such as refrigerators, certain power tools, and pumps. These devices will draw substantially more power at startup, if only for a short time, so you need to check the surge wattage for both your devices and the power station.
3. Calculate your ideal battery size
Each power station has an output wattage and a watt-hour (Wh) capacity. When you’re considering power station sizes, consider how long you want to keep your devices running to determine exactly how much energy you’ll need for a single charge.
Also: I always keep these 3 devices plugged into my power station – here’s why
You can calculate the estimated runtime by dividing your usable battery capacity by the average power draw:
ERT = UBC/APD
Where:
- ERT = Estimated runtime
- UBC = Usable battery capacity
- APD = Average power draw
ZDNET’s lab testing found that most power stations have a usable capacity between 80% and 95%. You can conservatively assume a power station has 85% usable efficiency when powering AC devices, so calculate your estimated runtime accordingly.
Also: This Anker power bank will keep your lights on in an outage
For example, a 2,000Wh power station may have a usable capacity of 1,700Wh (85%). If you divide that by a 380W load, you can expect about 4.5 hours of use from that power station.
1,700Wh/380W = 4.5 hours
You can choose the optimal power station capacity for your use case by considering the runtime you need out of your battery. If you need one to power 380W continuously for 9 hours, you’ll need a power station of at least 3.4kWh, which is twice the conservative 85% usable capacity of a 2,000Wh power station.
There are also online calculators to help you determine the size of a power station for your situation, including Power Station Sizer.
