Before you shop for anything, figure out this one number: how many watt-hours you actually need to get through an outage. Skip this step and you’ll either overpay for capacity you’ll never use, or end up with a battery that dies four hours into a storm.
Start with what actually needs power
You don’t need to back up your whole house. You need to back up the stuff that matters when the grid goes down: the fridge, some lights, your router and phone chargers, maybe a sump pump or a CPAP machine. Make a short list — most households land on 4 to 8 items.
Add up the watts
Every appliance has a wattage rating, usually on a sticker on the back or bottom, or in the manual. As a rough guide (check your own appliances — these vary a lot by model and age):
- Refrigerator: 100–200 running watts, with a startup surge of 800–1,200 watts
- Wifi router + modem: 20–30 watts
- LED lights: 5–10 watts each
- Laptop charger: 60–100 watts
- CPAP machine: 30–60 watts
- Sump pump: 800–1,500 running watts, with a surge close to double that
Two numbers matter here: running watts (what it draws once it’s on) and surge watts (the spike when a motor first kicks on). A battery or power station has to handle both, or it’ll trip and shut off the moment your fridge compressor kicks in.
Turn watts into watt-hours
Capacity is usually listed in watt-hours (Wh) or kilowatt-hours (kWh). To estimate how long a battery will last, divide its capacity by how many watts you’re drawing at once — that gives you hours of runtime. Example: a 1,000Wh battery running a 150-watt fridge non-stop would last about 6–7 hours. But a fridge doesn’t run constantly, it cycles on and off, so real-world runtime is usually 2–3x longer than that math suggests.
A decent starting target for a short outage (a few hours to overnight): 1,000–2,000Wh. For a multi-day outage where you want the fridge, some lights, and devices covered: 2,000–5,000Wh or more, ideally with a way to recharge it along the way (solar panels, or your car).
Portable power station vs. whole-home battery
This is really a budget and scope question:
- Portable power station (the box-with-handle kind): good for a handful of circuits — fridge, router, lights, charging. No electrician needed; you plug things into it directly or run an extension cord. Ceiling is usually a few thousand watt-hours.
- Whole-home battery + transfer switch: ties into your electrical panel and can run large parts of the house, including hardwired stuff like a well pump or HVAC. Needs a licensed electrician to install. Bigger capacity, bigger price tag.
If your outages are occasional and short, and you mainly care about the fridge and staying connected, a portable power station is usually the more sensible starting point. If you get frequent multi-day outages, or you’re running medical equipment that can’t lose power, the whole-home setup is worth the extra cost and hassle.
The math, in one line
Add up the running watts of what you want to power, multiply by how many hours you want to run it, and that’s your target watt-hours — with some buffer for surge and cycling. Everything else — brand, price, features — comes after you know that number.
This is general guidance based on typical appliance specs, not a review of any specific product. Check the actual wattage on your own appliances before you buy anything — it varies by model.