How do I calculate what size power station I need?

List every device you want to power and its wattage. Multiply each device's wattage by the hours you plan to use it (Wh = Watts x Hours). Add up all the watt-hours. Then multiply by 1.2 to account for inverter efficiency losses. The result is your minimum capacity in Wh.

What does Wh mean on a power station?

Wh (watt-hours) measures total energy capacity. It tells you how much power a station can deliver over time. A 1000Wh station can run a 100W device for 10 hours, or a 500W device for 2 hours. Higher Wh means longer runtime for the same load.

Is it better to oversize or undersize a power station?

Always oversize. Plan for 20-30% more capacity than your calculated needs. Batteries degrade over time, real-world efficiency is lower than rated specs, and you will likely add devices in the future. An oversized station also runs more efficiently since it is not constantly at full load.

Power Station Size Calculator: How Many Watt-Hours Do You Need?

The biggest mistake first-time buyers make is buying a power station that is too small (or too large) for their needs. This guide helps you calculate the right size.

The Simple Formula

Watt-hours needed = Device wattage x Hours of use

Add up all your devices, and you have your minimum capacity requirement. Then add a 20% buffer for efficiency losses (inverter conversion, cable resistance, battery degradation).

Common Device Power Draws

Device	Wattage	4 Hours Use	8 Hours Use
Smartphone charger	20W	80Wh	160Wh
Laptop	60W	240Wh	480Wh
Wi-Fi router	15W	60Wh	120Wh
LED light bulb	10W	40Wh	80Wh
Portable fan	40W	160Wh	320Wh
Mini-fridge	60W avg	240Wh	480Wh
Full-size fridge	150W avg	600Wh	1,200Wh
CPAP machine	40W	160Wh	320Wh
TV (50 inch)	110W	440Wh	880Wh
Electric blanket	200W	800Wh	1,600Wh
Coffee maker	1,000W	50Wh (3 min)	50Wh
Microwave	1,000W	100Wh (6 min)	100Wh

Scenario Calculations

Weekend Camping (2 nights)

Device	Wattage	Hours/Day	2-Day Total
Phone charging (x2)	40W	2 hrs	160Wh
LED camp lights	20W	6 hrs	240Wh
Portable fan	40W	8 hrs (night)	640Wh
Mini-fridge	60W	24 hrs	2,880Wh

Total: 3,920Wh with fridge, or 1,040Wh without.

With the 20% buffer: 4,700Wh with fridge, 1,250Wh without.

Recommendation without fridge: EcoFlow Delta 3 Plus (1,024Wh) or Bluetti AC180 (1,152Wh)

Home Power Outage (8 hours)

Device	Wattage	Hours	Total
Fridge	150W avg	8 hrs	1,200Wh
Wi-Fi router	15W	8 hrs	120Wh
Phone charging (x3)	60W	3 hrs	180Wh
LED lights (3 bulbs)	30W	8 hrs	240Wh

Total: 1,740Wh. With buffer: 2,088Wh.

Recommendation: Bluetti AC200L (2,048Wh) or Jackery Explorer 2000 v2 (2,042Wh)

Day Trip / Remote Work

Device	Wattage	Hours	Total
Laptop	60W	6 hrs	360Wh
Phone	20W	1 hr	20Wh
Portable speaker	10W	4 hrs	40Wh

Total: 420Wh. With buffer: 504Wh.

Recommendation: Jackery Explorer 600 Plus (632Wh) or Bluetti AC70 (768Wh)

Quick Sizing Guide

Your Need	Minimum Capacity	Recommended Range
Phone + laptop only	200-300Wh	EcoFlow River 3
Light camping (no fridge)	500-800Wh	Bluetti AC70
Camping with fridge	1,000-1,500Wh	EcoFlow Delta 3 Plus
Home backup (4-6 hrs)	1,000-1,500Wh	Bluetti AC180
Home backup (8-12 hrs)	2,000-4,000Wh	Bluetti AC200L
Whole-home backup	4,000Wh+	EcoFlow Delta Pro 3

Pro Tips

Round up, not down. If your calculation shows 900Wh, buy at least a 1,000Wh station.
Fridges are the big variable. With a fridge, you need at least double the capacity versus without.
Solar extends runtime. A 200W panel adds 800-1,200Wh per sunny day, effectively doubling a 1,000Wh station's daily capacity.
Efficiency losses are real. AC inverter conversion wastes 10-15% of stored energy. USB output is more efficient.

Related reading: See our best power stations under $500 and best power stations under $1,000 for specific recommendations at every budget.