What Size Power Station Do I Need? A Simple Wattage and Runtime Method (With Examples)

Affiliate disclosure: Some links on this page are affiliate links. If you buy through them, we may earn a commission at no extra cost to you. We haven’t tested these products hands-on. Power station specs and prices come from the official US brand pages, and appliance wattages come from published brand charts. All were checked on October 18, 2026. Sources are at the end.

Quick answer (TL;DR)

You need to match two numbers:

1. Output (watts): the station’s continuous rating must cover everything running at once, and its surge rating must cover your biggest motor starting up (fridges, pumps, AC).
2. Capacity (watt-hours): add up watts × hours for each device, divide by 0.85 for inverter losses, then multiply by 1.2 for a 20% safety margin.

Rough guide for US homes (120V):

• About 1kWh: router, CPAP, lights and phones overnight
• About 2kWh: add a refrigerator for most of a day
• 3–5kWh: fridge plus kitchen appliances for a full day or more
• 120/240V, expandable 4kWh+: well pumps, central AC, multi-day outages

Want model picks? Jump to match your number to a power station or see our best portable power station roundup.

Watts vs Watt-Hours: The Two Numbers That Matter

Most sizing mistakes come from mixing these up.

• Watts (W) measure power: how hard a device pulls right now. A power station’s continuous output (for example, 2,400W) is the most it can deliver at once. Its surge output (for example, 4,800W) is a short burst for motors starting up.
• Watt-hours (Wh) measure energy: how much is stored. A 2,048Wh battery could, in theory, deliver 2,048W for one hour or 100W for about 20 hours.

Think of watts as the width of the pipe and watt-hours as the size of the tank. You need a pipe wide enough for your appliances and a tank big enough to last the outage.

Step 1: List What You’ll Actually Run

Write down only what you truly need during an outage. Then find each item’s wattage:

• Best source: the label on the device or its power adapter. If it only lists volts and amps, multiply them. In the US, watts ≈ 120V × amps for plug-in appliances.
• For fridges: use the yellow EnergyGuide label. Divide its kWh-per-year figure by 365 to get kWh per day, then multiply by 1,000 to get Wh per day. This beats guessing, because a fridge’s compressor cycles on and off.
• Most accurate: a plug-in watt meter shows real-world draw.

Typical Appliance Wattages (US, 120V)

These are published brand estimates. Your appliances may differ, so check the label.

Jackery also notes that most home fridges run their compressors only 30–50% of the time. That’s why the EnergyGuide label gives a better daily figure than running watts × 24.

Step 2: Check Peak Watts and Surge

Add up the running watts of everything that could be on at the same time. Your power station’s continuous output must be higher than that total.

Then find your biggest starting surge (usually a fridge, pump or AC). The station’s surge rating must cover it, plus whatever else is already running.

Example: a fridge running at 200W might briefly pull 400–800W at startup (2–4×). A sump pump can spike to 4,100W.

240V matters: many US well pumps, central AC units and some dryers run on 240V. Only split-phase 120/240V units such as the EcoFlow DELTA Pro 3, Jackery Explorer 5000 Plus or Anker SOLIX F3800 Plus can power them. Those connections should go through a transfer switch installed by a licensed electrician.

Step 3: Calculate Your Daily Watt-Hours

For each device:

Wh = running watts × hours used

Add them up. Then use this formula to get the battery size you should shop for:

Battery size needed (Wh) = (total daily Wh ÷ 0.85) × 1.2

• ÷ 0.85 allows for inverter efficiency. The inverter loses some energy turning battery DC into 120V AC, so we assume about 85% reaches your devices. BLUETTI’s own runtime formula uses the same 85% inverter efficiency figure.
• × 1.2 adds a 20% safety margin for outages that run long, cold-weather losses and appliances that draw more than their label says.

The same formula powers the OutageReady size calculator. These are planning assumptions, not brand specs. Some brand tables are more conservative. Jackery’s own fridge runtime table (2,042Wh running a 200W fridge for 7.7 hours) works out to about 75% usable.

Step 4: Calculate Runtime

To flip it around and see how long a given station will last:

Runtime (hours) = capacity (Wh) × 0.85 ÷ load (W)

Our estimates using the formula above. The runtime formula has no safety margin, so treat these as best-case figures. Pumps and fridges cycle, so real runtimes are usually longer than “continuous” figures.

Worked Examples: Three Real Outage Scenarios

All three are example scenarios. Swap in your own appliance numbers.

Example 1: Essentials Overnight (12 Hours)

Battery size needed: (1,070 ÷ 0.85) × 1.2 ≈ 1,511Wh. Peak output: about 219W, so any unit here can handle it.

Verdict: this is a job for the 2kWh class (EcoFlow DELTA 3 Max or Jackery Explorer 2000 v2), which covers the 1,511Wh target with room to spare. A 1kWh unit falls short. Even without the laptop, the need is (870 ÷ 0.85) × 1.2 ≈ 1,228Wh. An Explorer 1000 v2 (about 910Wh usable) would technically run that 870Wh load, but with no safety margin.

👉 Check price: Jackery Explorer 1000 v2 → · Check price: EcoFlow DELTA 3 Max →

Example 2: 24-Hour Outage With a Refrigerator

Battery size needed: (3,211 ÷ 0.85) × 1.2 ≈ 4,533Wh. Peak output: microwave (1,000W) + fridge running (up to ~400W) + small loads ≈ 1,500W. Keep the microwave and coffee maker from running at the same time. The fridge’s startup surge also needs headroom.

Verdict: you’re in 4.5kWh territory. The Jackery Explorer 5000 Plus (5,040Wh) covers the full target, margin included. The EcoFlow DELTA Pro 3 (4,096Wh, about 3,482Wh usable) runs the 3,211Wh load, but without the full 20% margin. Add an extra battery if you want the safety margin.

Two cheaper routes:

• Trim the microwave and coffee maker and a 3kWh unit such as the Jackery HomePower 3000 (about 2,611Wh usable) covers most of the remaining 2,711Wh load.
• Pair a 2kWh station with solar. With 440W of panels, EcoFlow’s DELTA 3 Max bundle could recover roughly 1,200–1,500Wh on a sunny day (our estimate). See our solar generator for home guide, or browse the best portable power station with solar panel bundles.

👉 Check price: EcoFlow DELTA Pro 3 → · Check price: Jackery HomePower 3000 →

Example 3: Storm Night With a Sump Pump

A 1/2 HP sump pump runs at about 1,050W and can spike to 2,150–4,100W on startup. How long it runs depends entirely on how much water comes in. Say it runs 10 minutes per hour during a heavy storm:

1,050W × (10/60) × 24 hours = 4,200Wh per day. That means about (4,200 ÷ 0.85) × 1.2 ≈ 5,929Wh of battery.

Verdict: surge rules out the 1kWh class. The Explorer 1000 v2’s 3,000W surge may not start it. Energy needs point to an expandable system of about 6kWh or more. A Jackery Explorer 5000 Plus (5,040Wh, 14,400W surge) on its own falls about 900Wh short of the target, so pair it with a Battery Pack 5000 Plus. An EcoFlow DELTA Pro 3 with an extra battery is another option. If your pump runs less often, a 2kWh unit with 4,400W+ surge can cover shorter outages. Check your pump’s label for its actual starting watts.

👉 Check price: Jackery Explorer 5000 Plus →

Step 5: Match Your Number to a Power Station

All specs and prices are from the official US brand pages, at time of writing (checked October 18, 2026).

The “battery size need” column is your result from Step 3 (margin already included). The “daily load covered” column works backwards: capacity × 0.85 ÷ 1.2.

For full pros and cons of each, read our best portable power station roundup.

Common Sizing Mistakes to Avoid

• Ignoring surge. A station with plenty of Wh can still refuse to start a fridge or pump.
• Using fridge running watts × 24. Compressors cycle, so use the EnergyGuide label.
• Forgetting losses. Always divide by 0.85 for inverter losses.
• Skipping the safety margin. Outages run long. The × 1.2 step builds in a 20% buffer. A way to recharge (solar, expansion batteries) adds more breathing room.
• Assuming 240V support. Most portable units are 120V only.
• Relying on any battery for life-critical devices without checking. Jackery’s product pages say its stations are not recommended for medical or life-support equipment. Ask your device maker and doctor.

Verdict

For most US households, a 2kWh power station is the right starting size. It covers essentials plus a fridge for most of a day. Our top value pick at that size is the EcoFlow DELTA 3 Max ($899 at time of writing).

If your list includes a sump pump, well pump or central AC, size up to an expandable 120/240V system like the EcoFlow DELTA Pro 3 or Jackery Explorer 5000 Plus. If you only need CPAP, router and lights, a 1kWh unit saves you money.

👉 Check price: EcoFlow DELTA 3 Max →: the best fit for most homes.

Sources and Verification

Checked October 18, 2026. Prices at time of writing.

• Appliance wattages (router, modem, CPAP, LEDs, phone, laptop, TV, microwave, coffee maker, space heater, window AC, sump/well pumps, furnace fan): Jackery Appliance Wattage Chart, https://ca.jackery.com/blogs/knowledge/appliance-wattage-chart. Router/modem: https://www.jackery.com/blogs/buying-advice/can-jackery-power-wifi-router-modem
• Fridge running watts, 2–4× startup, 30–50% duty cycle, 2000 v2 runtime table: https://www.jackery.com/blogs/buying-advice/can-jackery-power-refrigerators-and-freezers
• 85% inverter efficiency in BLUETTI’s runtime formula: https://www.bluettipower.com/products/ac180 (FAQ Q4)
• Kettle and hair dryer wattages: https://us.ecoflow.com/products/delta-3-plus-portable-power-station
• Power station specs and prices: EcoFlow DELTA 3 Max, DELTA 3 Plus, DELTA Pro 3 (us.ecoflow.com). Jackery Explorer 1000 v2, 2000 v2, HomePower 3000, Explorer 5000 Plus (jackery.com). Anker SOLIX F3800 Plus (ankersolix.com). Full URLs are in our best portable power station sources table.

Assumptions, not brand figures: the 0.85 inverter-efficiency factor and 1.2 safety margin (matching the OutageReady calculator), the example 550 kWh/year fridge, the 10-minutes-per-hour sump duty cycle and the solar recovery estimate.

FAQ