How Big a Power Station Do I Need for a Power Outage?

Safety review, August 9, 2026: Bemo Editorial manually checked the medical-device and electrical cautions against FDA guidance and manufacturer documentation. Never treat a consumer runtime estimate as validated life-support backup; confirm the exact device plan with the care team and manufacturer.

Most households supporting a router, phones, a laptop, and LED lighting should begin their calculation in the 300Wh to 700Wh range. Add a refrigerator, and the result often moves toward the 1,000Wh class or above. Those are starting ranges, not purchase recommendations. The correct size comes from your measured watt-hours, the highest simultaneous wattage, and the largest startup surge.

Do not shop from the word 1000 in a model name. It can refer loosely to watt-hours, watts, or neither. Read the specification table.

For the wider outage plan, including generators, food safety, heat, and renter constraints, start with Power Outage Solutions: The Complete Blackout Guide.

The two numbers your power station must satisfy

1. Inverter output in watts

Continuous AC output must cover every AC load running at the same time. If a router draws 12W, a laptop 60W, and a refrigerator 140W while its compressor runs, the simultaneous running load is 212W.

Motors and compressors can demand substantially more at startup. The power station’s surge rating and surge duration must accommodate that event. A marketing mode that lowers voltage to keep a resistive appliance running is not equivalent to cleanly supporting a compressor or sensitive electronics.

2. Battery capacity in watt-hours

Capacity determines the energy budget. A 500W load running for two hours consumes 1,000Wh before losses. A 10W load running for 20 hours consumes 200Wh.

Real delivered energy is lower than the label because the inverter, electronics, cabling, temperature, and connected chargers consume or lose energy. Battery age and leaving reserve also reduce available runtime.

Progression from phone and lantern to router and laptop, medical equipment, and refrigerator with increasingly large battery stations — Choose output for the largest simultaneous load and capacity for the total energy required.

Use this power-station sizing formula

Create one row per device:

device energy = average watts × hours used

Then:

total load Wh = sum of every device's energy
planning battery Wh = total load Wh ÷ usable-energy factor

Using 0.8 as an initial usable-energy factor gives 20 percent for losses and reserve. It is a planning convention, not a promise that every product delivers exactly 80 percent through every port.

Worked example: communications and work

router and modem: 15W × 12h = 180Wh
laptop:           50W × 4h  = 200Wh
two phones:                    35Wh
LED lantern:       5W × 6h  =  30Wh
total load:                    445Wh
planning capacity: 445 ÷ 0.8 = 557Wh

A unit around 600Wh would be the mathematical starting point. A 700Wh to 800Wh model adds more reserve, while 1,000Wh may be unnecessary unless you add refrigeration, longer runtime, or an uncertain recharge schedule.

Worked example: refrigerator plus essentials

Assume a measured refrigerator uses 1.1kWh per 24 hours, but you plan to power it for 12 hours during a rolling outage:

refrigerator: 1,100Wh × 0.5 = 550Wh
router:          12W × 12h = 144Wh
phones and light:             55Wh
total load:                   749Wh
planning capacity: 749 ÷ 0.8 = 936Wh

That points toward a 1,000Wh-class station, provided its inverter also handles compressor startup. For a full day without recharging, the same refrigerator moves the calculation well above 1,000Wh.

Measure the loads that matter

How to measure common outage loads
Example load	Best measurement	Sizing trap
Phone and USB light	USB meter or charger specifications	Counting battery mAh without converting voltage and losses
Modem and router	Plug-in watt meter over several hours	Assuming internet service remains available upstream
Laptop	Energy used through a normal work session	Using charger maximum wattage as constant draw
Refrigerator	Plug-in energy monitor over at least 24 hours	Missing compressor surge or measuring only one cycle state
Sump pump	Manufacturer data plus qualified surge measurement	Ignoring motor starting demand and discharge frequency
Medical device	Exact manufacturer and provider guidance	Applying a generic internet estimate to a critical device

A plug-in energy monitor is one of the highest-return purchases in this process. Measure normal use before storm season and record both accumulated kWh and observed peak watts. Do not place a meter between equipment when either manufacturer’s instructions prohibit it.

Find plug-in watt meters on AmazonView on AmazonIf you click this link and buy, we may earn a commission at no additional cost to you.

Nameplate watts are not always normal watts

A power adapter labeled 100W can be capable of delivering 100W while a charged laptop uses far less. A refrigerator nameplate may describe a rated condition rather than its daily energy use. Measure energy over the same pattern you expect during an outage.

Duty cycle changes everything

Refrigerators, freezers, pumps, and some medical equipment cycle. Multiplying active running watts by 24 hours can greatly overstate consumption. Measuring during an idle period can dangerously understate it.

What capacity class fits each plan?

200Wh to 300Wh: communication kit

Best for phones, tablets, LED lights, and limited router or laptop use. It is light enough to carry easily and often offers better value than using a large station for tiny USB loads.

Do not choose this class for a refrigerator merely because the inverter can momentarily start it. Capacity will be the constraint.

500Wh to 800Wh: workday essentials

This class makes sense for a router, several device charges, lighting, and a laptop through a workday. It can also support selected low-wattage devices, but refrigeration runtime is limited and must be measured.

About 1,000Wh: refrigerator plus electronics

The 1kWh class is the common crossover point for home backup. Current examples pair roughly 1,024Wh to 1,070Wh with 1,500W to 1,800W output. EcoFlow publishes 1,024Wh and 1,800W for the DELTA 3 Plus.^[1] Jackery publishes 1,070Wh and 1,500W for the Explorer 1000 V2.^[2]

That does not mean either runs every refrigerator for a day. Capacity, actual refrigerator use, surge, and losses still control the answer.

2,000Wh and above: longer backup or multiple appliances

Move above 1kWh when measurements justify it, recharging opportunities are limited, or you need multiple days of communication and refrigeration. Weight, storage space, circuit input while fast-charging, and total system cost become more important.

Expansion batteries help when the base inverter is already adequate. They do not increase output on every ecosystem, so confirm what expansion changes.

Loads that make batteries grow very quickly

Resistive heat is simple arithmetic and usually poor battery economics:

1,500W space heater × 1 hour = 1,500Wh before losses

Electric kettles, hair dryers, toasters, hot plates, and microwaves can also draw heavily, though some run only briefly. Air conditioners combine high running energy with compressor startup. Prioritize the load that protects health or prevents damage, and turn convenience loads off.

Medical devices require a separate calculation

FDA recommends checking with the device manufacturer or distributor about battery or generator use.^[4] Heated humidifiers, pressure settings, accessories, and AC versus DC conversion can change runtime. Do not treat a consumer station’s display estimate as a medical guarantee.

Build redundancy, alarms, a recharging plan, and a relocation threshold with the clinician and device provider. Critical equipment may require a backup approved specifically for that device.

Five mistakes that cause undersizing

Using inverter watts as battery capacity. A 2,000W inverter does not contain 2,000Wh.
Ignoring startup surge. Motors can trip an inverter that appears large enough from running watts.
Adding every appliance but no hours. Energy is power multiplied by time.
Trusting displayed runtime before testing. The estimate changes with load and conditions.
Assuming solar input equals the panel label. Weather, angle, temperature, shading, and controller limits reduce harvest.

The buying checklist

Before comparing models, write down:

required labeled capacity after your loss allowance;
continuous AC watts;
required surge capability;
number and type of ports;
acceptable transfer time, if used as a UPS;
AC and solar recharge limits;
weight you can actually move;
operating and storage temperatures;
exact independent safety certification;
warranty and battery-cycle terms;
expansion path, if genuinely needed.

Then compare current recommendations in Best Portable Power Station for Power Outages.

Final answer

For phones, lights, a router, and a laptop, start the math around 300Wh to 700Wh. For those loads plus a measured refrigerator, about 1,000Wh is a common starting class. For a full day of refrigeration, pumps, or several appliances, calculate from measurement because 2,000Wh or more may be justified.

The best size is the smallest station that clears your simultaneous watts and surge, supplies your required watt-hours with reserve, and can be recharged safely before the next outage window.

FAQ (Frequently Asked Questions)

Is a 1,000-watt power station enough for a power outage?

The 1,000-watt label usually describes inverter output, not battery capacity. It may run a router, laptop, lights, and some refrigerators if their combined running and startup demand stays within the output limit. Runtime depends on watt-hours. Check both ratings and measure your actual loads.

How many watt-hours do I need for a 24-hour power outage?

Multiply each device’s average watts by the hours it will operate, add the results, then divide by a conservative usable-energy factor such as 0.8 for initial planning. A 10-watt router for 24 hours uses 240Wh before losses. A cycling refrigerator must be measured over time rather than treated as a continuous nameplate load.

What size power station will run a refrigerator?

There is no universal size. The inverter must handle the refrigerator’s compressor startup, and the battery must store enough energy for the intended runtime. Measure the refrigerator over at least 24 hours with a suitable energy monitor, then include reserve and conversion loss.

What is the difference between watts and watt-hours?

Watts describe the rate of power at a moment. Watt-hours describe energy used or stored over time. Inverter watts determine whether a load can run; battery watt-hours largely determine how long it can run.

Should I buy twice the battery capacity I calculate?

Not automatically. Add a documented margin for conversion losses, battery reserve, uncertain loads, cold weather, and aging. Doubling may be sensible when the load is critical or future expansion is likely, but it adds cost and weight. Better measurements usually save more money than a blanket two-times rule.

Can I size a power station for a CPAP from its watt rating?

Do not rely on a generic CPAP estimate. Humidification, heated tubing, pressure, mask leakage, power supply, and DC versus AC operation can change consumption. Use the exact medical-device manufacturer’s guidance and build a clinician-approved outage plan.

REFERENCE NOTES