Sizing a power setup comes down to two numbers: watts (how much power your devices pull at once) and watt-hours (how much energy you need over time). Get those right and the rest is picking a product that fits. This guide walks through the math, the common mistakes, and the tradeoffs. Specs below are general examples; confirm current numbers for any product on the official Jackery site.
The Three Numbers That Matter
- Running watts: what a device draws while operating. Compare this to the power station's continuous output rating.
- Surge (starting) watts: a short spike, common in motors and compressors (fridges, pumps, power tools, air conditioners). Compare this to the station's surge rating.
- Watt-hours (Wh): energy. A 100 W device running for 5 hours uses about 500 Wh.
Step 1: List What You Need to Run
Write down only what matters for your scenario: an outage, a camping weekend, an RV trip, a job site. Skip the nice-to-haves at first.
Find the wattage
- Check the label or manual for watts. If you only see amps and volts, multiply them (for example, 1.5 A × 120 V = 180 W).
- For a more accurate figure, use a plug-in watt meter, which is inexpensive and shows real draw.
- Note whether the device has a surge. Anything with a motor or compressor probably does.
Typical ballpark draws
These are rough, widely cited ranges. Your own devices will vary, so measure when you can.
| Device | Typical running draw | Notes |
|---|---|---|
| Phone charging | 5–20 W | Very low energy use |
| Laptop | 45–100 W | Varies with workload |
| LED lights | 5–15 W each | Efficient |
| Wi-Fi router and modem | 10–30 W combined | Often runs 24/7 |
| Full-size refrigerator | 100–200 W while running | Surge at startup; cycles on and off |
| CPAP machine | 30–60 W (more with heated humidifier) | Check your model; ask your provider about backup needs |
| Space heater, hair dryer, toaster | 1,000–1,800 W | Usually a poor fit for portable batteries |
Step 2: Do the Runtime Math
- Add up running watts for everything that could run at the same time. This is your minimum continuous output requirement.
- Add the largest surge on top of the other running loads to check the surge requirement.
- Estimate hours of use per device, then multiply watts × hours to get Wh for each. Add them up.
- Apply a loss factor. Inverter conversion and other losses mean usable energy is below the rated capacity. A planning figure of about 80–85% usable is common, but actual efficiency varies by product and load.
Formula: Runtime (hours) ≈ (battery Wh × 0.85) ÷ load watts.
Worked example
Say you want to run a fridge, router, a few lights, and phone charging overnight and through the next day.
- Fridge: roughly 1,200 Wh per day if it actually draws about 50 W on average when cycling (a measured figure is better than this guess).
- Router: 15 W × 24 h = 360 Wh.
- Lights: 20 W × 6 h = 120 Wh.
- Phones: about 40 Wh.
The total is roughly 1,700 Wh per day. Divided by 0.85, you would want about 2,000 Wh of rated capacity for one day. Treat this as an illustration, not a prediction. For a deeper outage walkthrough, see How many watt-hours do you need to get through a power outage?
Step 3: Match Output to the Biggest Load
A battery with plenty of watt-hours can still fail to start a device if its output is too low. Check both ratings. Two common cases:
- Air conditioners: high startup surge makes these demanding. See Can a Jackery run an RV air conditioner?
- Power tools: saws and compressors have heavy surges. See Can a Jackery run power tools on a job site?
Whole-home loads (central air, electric ovens, water heaters) are generally beyond a portable station. See Can a Jackery power a whole house? and Home Backup Kit vs Portable Power Station.
Recommended for youPortable Power Station vs Solar Generator: What's the Difference and Which Should You Buy?Step 4: Plan Recharging
Capacity only helps if you can refill it. Options include wall power, car charging, and solar. Solar input depends on panel wattage, sun angle, weather and season, so real-world output is often well below the panel's rating. Rough estimate: panel watts × usable sun hours × about 0.7 gives daily Wh.
- How many panels? How many solar panels do you need to charge a Jackery?
- Wiring several panels: series vs. parallel. Always stay within the station's stated input voltage and current limits.
Tradeoffs to Weigh
Bigger battery vs. smaller and lighter
More capacity means longer runtime but more weight, higher cost and slower recharging. Sizing to your real needs, plus a modest buffer, usually beats buying the largest unit.
Panels vs. expansion batteries
If outages are short, extra storage may help more. If they are long or you are off-grid, recharging matters more. Details in Solar Panels vs Expansion Batteries.
Battery vs. gas generator
Batteries are quiet and safe for indoor-adjacent use, but their runtime is finite. Gas generators can run longer with fuel but bring noise, fumes and fuel storage. Never run a gas generator indoors or in a garage because of carbon monoxide risk. See Solar Generator vs Gas Generator and Portable Power Station vs Solar Generator.
Safety and Medical Notes
- For medical devices, talk to your doctor or equipment provider about backup power. Do not rely on a calculation alone.
- Do not connect a portable station to home wiring without a properly installed transfer switch. Consult a licensed electrician.
- Follow the manufacturer's manual for operating temperatures, ventilation and charging.
Quick Sizing Checklist
- List essential devices.
- Measure or look up running and surge watts.
- Total the simultaneous running watts and check the largest surge.
- Multiply watts × hours for daily Wh, then divide by about 0.85.
- Decide how you will recharge.
- Compare models, and confirm specs, ports and current details on the official Jackery site.
Ready to compare? See Best Jackery Power Station: Top Picks by Budget, Capacity and Use Case, or start broader with Choosing the Right Power Setup: Types & Options.
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