Portable power station vs. gas generator: watt-hours, runtime, cost and when each makes sense

Battery "power stations" (sometimes marketed as "solar generators") have become a popular alternative to small gas generators. They're quiet, produce no exhaust, and can be used indoors. But they store a fixed amount of energy, and once it's gone you need a way to recharge. This guide explains how to compare the two, so you can pick the right tool, or the right combination.

Two different numbers: watts and watt-hours

Gas generators are rated in watts: how much power they can deliver at once. As long as you keep adding fuel, they keep going.

Power stations have two ratings:

• Output (watts): the continuous and surge power the inverter can deliver, such as 1,800 W continuous and 3,600 W surge.
• Capacity (watt-hours, Wh): the total energy stored, such as 1,500 Wh or 3,000 Wh.

Capacity is the number most people overlook. A 1,000 Wh station can run a 100 W load for roughly 8 to 9 hours after inverter losses, but a 1,000 W load for well under an hour.

Runtime math

A simple estimate:

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

The 0.85 factor accounts for inverter and conversion losses. It varies by product, so check the manufacturer's efficiency figure if one is published.

Load	Typical watts	Runtime on 1,000 Wh	Runtime on 3,000 Wh
Phone and laptop charging	60	~14 hrs	~42 hrs
Internet router plus LED lights	40	~21 hrs	~64 hrs
CPAP without humidifier	40	~21 hrs	~64 hrs
Refrigerator (average, cycling)	100 to 150	~6 to 8 hrs	~17 to 25 hrs
Window AC, small	500	~1.7 hrs	~5 hrs
Space heater	1,500	~0.6 hr	~1.7 hrs

The refrigerator figure uses average draw. The compressor might pull 700 W while running, but it cycles on and off. The station's surge rating must still handle the compressor's start.

Recharging: the real limit

When the station is empty, you have to recharge it:

• From a wall outlet, once power returns, or at a friend's home or a charging center.
• From solar panels. Real-world output is often well below the panel's rated wattage, depending on sun angle, weather, and temperature. A 400 W panel array might deliver roughly 1 to 2 kWh on a good day, and far less on a cloudy one.
• From a vehicle, via a 12-volt outlet. This is slow, often around 100 W.
• From a gas generator. Many people pair a small inverter generator with a station: run the generator a few hours a day to recharge, and use the station silently the rest of the time.

Solar makes a power station self-sustaining for small loads in sunny weather. It's much less reliable during storms, winter, or wildfire smoke.

Comparing fuel energy

To put capacity in perspective: the U.S. EIA lists gasoline at about 120,214 Btu per gallon. One kilowatt-hour equals about 3,412 Btu, so a gallon of gasoline holds roughly 35 kWh of chemical energy. Small generators convert only a fraction of that to electricity, often on the order of 15 to 25%, but even so, a few gallons of gasoline can produce more electricity than several large power stations store. That's why generators still win for long outages and heavy loads.

Strengths of power stations

• Safe indoors. No exhaust and no carbon monoxide, so they can sit next to a bed or a medical device.
• Silent. Good for apartments, campgrounds with quiet hours, and nighttime use.
• Instant and low-maintenance. No fuel to go stale, no oil changes, and no pull cords.
• Clean power. Most have pure sine wave inverters, which suit electronics and medical equipment.
• Some include UPS or pass-through functions to bridge outages without interruption.

Strengths of gas generators

• Sustained high output for well pumps, furnaces, AC units, and multiple appliances.
• Runtime limited only by fuel you can store and safely refuel.
• Lower cost per watt of output.
• 240-volt output on larger models, for transfer switches.

Safety differences

Gas generators produce carbon monoxide. The CDC reports more than 400 U.S. deaths each year from unintentional, non-fire CO poisoning, and says generators must be used only outside, more than 20 feet from windows, doors, and vents. Power stations avoid that risk, but they have their own safety rules: buy units certified by a recognized testing lab, don't cover them while charging, keep them away from water, and follow the manufacturer's temperature limits. Large lithium batteries should never be charged if damaged or swollen.

Which should you buy?

• Apartment dwellers, campers, and CPAP users with short outages: a power station, possibly with a solar panel.
• Homeowners with well pumps, sump pumps, or furnaces, or frequent multi-day outages: a gas or dual-fuel generator, ideally with a transfer switch.
• Many households: both. A mid-size power station for quiet nighttime and indoor loads, and a generator for heavy loads and recharging.

Cost comparison

Prices change quickly, but as a rough pattern:

• A 1,000 to 2,000 Wh power station often costs about as much as a mid-size gas generator.
• Large 3,000+ Wh stations and expandable systems can cost several times as much.
• Generators cost less up front per watt, but add fuel, oil, and maintenance.

Compare on what you actually need to run, and for how long. Use our calculator to total your loads, then decide whether stored energy, generated energy, or both fit your situation.

Battery care

Lithium power stations keep best when stored partly charged in a cool, dry place. Many manufacturers suggest topping up every few months. Check the charge before storm season, and run the station through a full charge and discharge occasionally, so you know its real capacity rather than the number on the box. Like any battery, capacity declines with age and cycles, so a station bought several years ago may hold noticeably less than when it was new.