If you've started shopping for a portable power station, you've probably noticed a problem: the specs are confusing, the prices are scary, and nobody seems to give you a straight answer about how big you actually need. One brand says you need 1000 watt-hours, another pushes you toward 3000. Some are $500. Some are $5,000. How do you know what's right for you?
This guide cuts through the noise. By the end, you'll know exactly how to size a power station to your real needs — without overspending on capacity you'll never use or under-buying something that can't keep up.
The Two Numbers That Matter
Every power station has two key specifications. Once you understand what these mean, the rest is just arithmetic.
Watts (W) — also called AC Output or Continuous Output
This is how much power the unit can deliver at any one moment. It determines what you can RUN, not for how long.
A 500W power station can run a 500W device, but can't simultaneously run two 300W devices (that would be 600W — over its limit).
A 2000W power station can run a microwave (typically 1000-1200W), a fridge (150W), and charge a few laptops at the same time without breaking a sweat.
Watt-Hours (Wh) — also called Capacity
This is how much TOTAL ENERGY the unit holds. It determines how LONG you can run things.
A 1000Wh battery can deliver 1000 watts for 1 hour, OR 100 watts for 10 hours, OR 50 watts for 20 hours. Same battery, totally different runtimes — depending on what you're plugging in.
The simple way to think about it:
Watts = the size of the firehose (how much power can flow at once)
Watt-hours = the size of the water tank (how much total water is in there)
You need enough of both — but the right balance depends on what you're trying to do.
Step 1: What Do You Actually Want to Run?
Before you shop, make a list. Be specific. Don't say "my fridge" — figure out what wattage your fridge actually draws.
Here are real-world wattages for common devices:
Device
Typical Wattage
LED lightbulb
8-15W
Phone charger
5-20W
Laptop
30-65W
Wi-Fi router
10-20W
CPAP machine
30-60W
TV (LED, 50")
60-120W
Mini fridge
50-100W
Full-size refrigerator
100-250W (average — they cycle on and off)
Electric blanket
50-100W
Microwave (small)
600-1200W
Electric kettle
1200-1500W
Hair dryer
1200-1875W
Coffee maker (drip)
600-1200W
Window AC unit
500-1500W
Space heater
1000-1500W
Power tools (drills, saws)
500-1500W
Well pump
500-1500W (with high startup surge)
Important note on appliances with motors: Anything with a compressor or motor (fridges, AC units, well pumps, power tools) has a startup surge that can be 2-3x its normal running wattage. A fridge running at 150W might briefly pull 600W when its compressor kicks on. Your power station needs enough headroom to handle these surges, or it'll shut off.
Step 2: Calculate Your Continuous Wattage Need
Add up the wattage of everything you want to run at the same time. That's your minimum AC output (W rating) for a power station.
Example A — Weekend camping setup:
LED lights: 30W
Phone chargers: 30W
Laptop: 60W
Small fan: 20W
Total: 140W continuous
A power station with 300W+ AC output handles this easily. Almost any unit on the market works.
Example B — Power outage essentials:
Refrigerator: 150W (assume 600W surge)
Wi-Fi router: 20W
LED lights: 50W
Phone/laptop charging: 100W
CPAP at night: 50W
Total: ~370W continuous, with 600W surge headroom needed
A power station with 1000W+ continuous output handles this. Look for "surge power" ratings of 1500W+ to handle the fridge compressor kicks.
Example C — Off-grid cabin or serious home backup:
Refrigerator: 150W (600W surge)
Microwave (occasional): 1000W
Well pump (occasional): 800W (1500W surge)
Lights and electronics: 200W
Power tools (occasional): 1000W
Peak need: ~2200W continuous, surge over 3000W
You need a power station rated 2000W+ continuous with surge handling of 3000W+. This is when you start looking at systems like the Bluetti AC200P or the Bluetti Apex 300.
Step 3: Calculate Your Capacity Need (Watt-Hours)
Now the second number. How LONG do you need everything to run?
The formula: Total wattage × Hours of runtime = Watt-hours needed
Then add about 20% buffer for real-world inefficiency.
Example A — Weekend camping (3 days, evenings only, ~6 hours/day):
140W × 6 hours × 3 days = 2,520Wh over 3 days
But you can recharge from solar each day, so you really only need ONE day of capacity
140W × 6 hours = 840Wh + 20% buffer = ~1000Wh
A 1000Wh unit like the Bluetti AC180 works perfectly. With a solar panel, you can recharge during the day for nearly indefinite operation.
Example B — 24-hour power outage essentials:
The trick with fridges is they don't run continuously. They cycle on and off, typically running about 30% of the time. So a 150W fridge actually averages closer to 50W over a day.
Fridge: 50W avg × 24 hours = 1200Wh
Wi-Fi: 20W × 24 hours = 480Wh
Lights: 50W × 6 hours = 300Wh
Charging devices: 100W × 4 hours = 400Wh
CPAP at night: 50W × 8 hours = 400Wh
Total: ~2780Wh for 24 hours, add 20% = ~3300Wh
You need a 3000Wh+ power station, or a smaller unit paired with solar panels to extend runtime. The Bluetti AC200P (2000Wh) gets you about 17 hours; expandable systems like the Apex 300 with battery expansion handle multi-day outages comfortably.
Example C — Multi-day off-grid or extended outage:
Once you're looking at 3+ days of essential power, you're in expandable-system territory. The math gets simpler: pick a base unit, then add battery expansion modules until you have enough capacity. Plan to recharge from solar during the day to extend operation indefinitely.
Step 4: Don't Forget Solar Recharging
A power station's capacity is the wrong way to think about long off-grid use. If you're going beyond 1-2 days, you need a way to REFILL the battery — and that's where solar comes in.
A 200W solar panel adds roughly 800-1200Wh of recharging per day in good sun. Two panels double that. With enough solar input, your power station can recharge faster than you drain it, making it effectively unlimited.
Most modern power stations accept 200-1000W+ of solar input. Check the max solar input spec when shopping — it tells you how fast you can recharge.
Quick guide:
For weekend trips, one 100-200W panel is plenty
For week-long off-grid, plan on 400-600W of solar
For permanent off-grid, you'll likely want 1000W+ of solar paired with an expandable system
Quick Cheat Sheet — Sizing by Use Case
Use case
Recommended size
Example
Phone/laptop charging on the go
300-500Wh
Small, ultra-portable units
Weekend camping (lights, phones, fan)
500-1000Wh
Bluetti AC180-sized
Tent/RV camping for several days
1000-2000Wh + solar
Bluetti AC180 or AC200P + SP200L
24-hour home outage (essentials)
2000-3000Wh
Bluetti AC200P or similar
Multi-day outage / cabin / off-grid
3000Wh+ expandable
Bluetti Apex 300 + B500K batteries
Whole-home backup with HVAC
5000Wh+ expandable
Multiple expandable units in parallel
The Bottom Line
For most people building a first off-grid power setup, here's the honest advice:
Start with 1000-2000Wh and 1500W+ AC output. This range handles weekend camping, short outages, and most off-grid needs. It's affordable, expandable later, and forgiving if you misjudged your usage.
Don't try to size for your worst-case "what if civilization ends" scenario on your first purchase. Buy for your real, realistic use case. Add capacity later if you find you need it — modern systems are designed to expand.
If you're still unsure what's right for you, send us your device list at sales@bunkermart.com and we'll help you size it specifically to your situation. No upsell pressure — we'd rather get you the right system the first time.
Browse our Portable Power Stations collection to see units across the size range, or check out Solar Panels & Kits for solar recharging options to pair with any unit.
