The Two Numbers You Must Understand
Watts (W) = what you can run
Continuous output tells you how much power the station can deliver at once. Your combined simultaneous load must fit within that limit. Motors and compressors can also require a brief startup surge.
Watt-hours (Wh) = how long you can run it
Battery capacity describes stored energy. A larger Wh number generally means longer runtime, but rated capacity is not the same as energy delivered from an AC outlet because conversion consumes some energy.
The Practical Buyer 4-Step Sizing Method
List only the devices you actually need
Use the device label, power adapter, manual or manufacturer specification. If the label provides volts and amps but not watts, a basic estimate is volts × amps = watts.
Add simultaneous running watts
Identify which devices may operate at the same time. The power station's continuous AC output needs to cover that combined demand.
Check startup or surge demand
Refrigerators, freezers, pumps, air conditioners and other motor-driven equipment can draw more power when starting. Check the appliance and power-station specifications rather than assuming running watts tell the whole story.
Calculate the energy you need
Multiply each device's average watts by the hours you expect to use it, then total the results. Add a reserve for conversion losses and unexpected use rather than sizing to the theoretical minimum.
The Core Calculation
If your essential loads require 1,700Wh of delivered energy, a theoretical 1,700Wh battery is too close to the edge. Inverter and system losses mean real AC runtime is lower than simple nameplate math suggests.
For quick planning, an 80–85% usable-energy assumption is a reasonable starting range for stable AC loads—not a guarantee. Jackery's current runtime guidance, for example, uses an 80% factor, while other Jackery sizing material uses roughly 85%.
Example: 1,700Wh ÷ 0.85 ≈ 2,000Wh. That points you toward roughly a 2kWh-class station, assuming its continuous and surge output also meet your load requirements.
Build Your Own Power Budget
| Device | Average watts | Hours used | Energy needed | Startup/surge? |
|---|---|---|---|---|
| Refrigerator | Enter measured average | Enter equivalent run time | W × hours | Yes — verify |
| Wi-Fi/router | Enter actual watts | Hours needed | W × hours | Usually low |
| LED lights | Enter total watts | Hours needed | W × hours | Usually low |
| Laptop/phones | Enter charger/load watts | Hours needed | W × hours | Usually low |
| Your next essential | _____ W | _____ h | _____ Wh | Check |
For cycling appliances such as refrigerators, a plug-in watt meter measured over time can provide a more useful estimate than simply multiplying maximum nameplate watts by 24 hours.
Practical Capacity Tiers
300–500Wh
Best suited to light-duty needs such as phones, tablets, laptops, routers, LED lighting and similar electronics.
500–1,000Wh
More breathing room for electronics, fans and selected small appliances. Useful when portability still matters.
1,000–2,000Wh
A stronger emergency/camping class for selected household essentials, provided the inverter can handle their output and surge requirements.
2,000–3,000Wh
A practical home-outage class for refrigeration, communications, lights and electronics with more meaningful runtime.
4,000Wh+
Better suited to heavier outage loads, longer runtime or expandable backup systems. Large capacity does not automatically make a system whole-home backup.
Don't buy by capacity alone
A 4,000Wh battery with insufficient inverter output still cannot run a load that exceeds its power limits. Capacity and output always need to be checked together.
Why Refrigerators Need Special Treatment
A refrigerator does not normally draw its maximum wattage continuously. The compressor cycles on and off, and startup demand can briefly exceed normal running demand. That makes a simple “watts × 24 hours” calculation potentially misleading.
For better planning, measure the refrigerator's consumption over a representative period when possible. Then make sure the power station can also tolerate the compressor's startup surge.
Three Sizing Mistakes to Avoid
Buying for watt-hours only
A large battery does not guarantee enough inverter output to start or operate every appliance.
Assuming nameplate capacity is fully usable
AC conversion and system overhead reduce delivered energy. Build in margin rather than sizing to exactly 100% of the battery label.
Ignoring recharge strategy
For multi-day use, recharge speed and available AC, vehicle or solar charging can matter nearly as much as battery size.
Buying for an extreme scenario you rarely need
More capacity means more cost and usually more weight. Size around your realistic essential-load plan, then add sensible reserve.
Which Guide Should You Read Next?
Need roughly a 1kWh portable unit?
See our four researched picks balancing performance, value and portability.
See the 1kWh-class picksNeed serious home-outage backup?
Compare our researched 2–4kWh outage-focused choices.
See the home-outage picksFrequently Asked Questions
Is a 1,000Wh power station enough?
It can be enough for light electronics, camping and selected short-duration emergency loads, but whether it is enough for you depends on the watts, runtime and surge demand of your actual devices.
How do I estimate runtime?
For a stable load, a planning estimate is usable battery energy divided by device watts. Manufacturer guidance commonly applies an efficiency factor because AC conversion reduces theoretical runtime.
Should I size from running watts or surge watts?
You need both. Continuous output must support sustained simultaneous loads, while surge capability must accommodate brief startup demand from applicable motors and compressors.
How much extra capacity should I buy?
Do not size exactly to the theoretical requirement. Conversion losses, variable appliance behavior and unexpected use justify a reserve. Measure actual consumption when possible and round up rather than down.
Does solar mean I can buy a smaller battery?
Not automatically. Solar production varies with weather, season, panel orientation and available sunlight. Treat recharge capability separately from the battery capacity needed to carry your critical loads when solar is unavailable.
How The Practical Buyer Chose This Method
This guide separates three issues that are often mixed together: energy capacity (Wh), continuous output (W), and startup/surge demand. We reviewed current manufacturer sizing and runtime documentation and intentionally present efficiency as an estimate rather than promising a fixed runtime.
Our goal is not to tell every reader to buy a larger battery. It is to help you build an essential-load plan first and then choose the smallest practical system that provides adequate output, runtime and reserve.
Research Sources
Primary sizing/runtime documentation: Jackery runtime guidance, Jackery selection guidance, and additional current Jackery battery-capacity/sizing documentation.
Research checked September 21, 2026. Appliance behavior and manufacturer specifications can change; verify current device and power-station specifications before purchase.