Portable power station: pick the size, not the brand

The first number is daily energy. Add up watts times hours for everything you want to survive an outage, and you have watt hours. Our load calculator does that arithmetic and prints the formula, so the result can be checked with a pencil. The second number is startup surge: a compressor draws several times its running watts for a fraction of a second, and the inverter has to survive that moment.

Those two numbers map onto two different specifications, and confusing them is the most expensive error in this category. A unit with plenty of capacity but a weak surge rating will hold the energy needed to run a refrigerator for hours and still refuse to start it.

A third number matters more than people expect: the inverter's continuous rating. Capacity tells you how long, the continuous rating tells you how much at once. A 2,000 Wh battery paired with a 500 W inverter is a big tank with a narrow tap.

Sorting by capacity is more useful than sorting by price, because capacity is what decides which appliances are physically possible. The table below lists the tiers, a few representative units, and the load each tier can carry overnight. Prices change weekly; watt hours do not.

Two rows in the same tier are not the same product. Capacity sets how long, the inverter sets how much, and the transfer time sets whether a computer notices. Those three columns decide the purchase; the badge on the front does not.

Marketing pages use the word peak loosely, and the loose use costs people real money. Three claims get mixed together.

Surge rating is what the inverter can deliver for a fraction of a second while a motor spins up. That is the number that matters for a refrigerator, a well pump or a circular saw. It is usually two to three times the continuous rating.

Power lifting, sometimes called X-Boost or similar, is a different trick: the inverter reduces output voltage so it can push more watts into a purely resistive load like a heater or a hair dryer. It cannot start a compressor, because a motor needs voltage to produce torque. A listing that says "runs 2,400 W" while the continuous rating is 1,800 W is usually describing this, not surge.

Battery peak output is a third number: the cells can deliver more than the inverter converts. Pair it with a weak inverter and the inverter is still the limit.

The practical test: find the continuous rating and the surge rating, and ignore every other wattage claim on the page. If surge is not stated, assume it is twice continuous at best.

The naming gives the game away. BLUETTI prints Power Lifting on the AC70 and the Elite 200 V2, and Anker prints SurgePad on the C300. Neither is a motor-start rating, and neither brand calls it surge. When a listing does not use the word surge, assume the unit has no stated motor-start capability.

Runtime equals capacity times usable depth times inverter efficiency, divided by the load. Usable depth for lithium iron phosphate is around 85 to 90%; inverter efficiency is around 85 to 90%. Multiply both and you keep roughly three quarters of the nameplate number.

Two adjustments matter in practice. A compressor cycles, so its average draw is lower than its running rating, which helps. But a cold kitchen in winter raises draw, and a battery below freezing charges slowly or not at all, which hurts.

That last row is the one to remember. A space heater empties any portable station in about an hour, which is why heat is the worst possible load for a battery and why none of these units should be bought as heating backup.

A standard US outlet is 120 V. A clothes dryer, an electric range, a central air conditioner and an EV charger need 240 V. No amount of capacity fixes that, and a bigger battery does not help. That is a wiring fact, not a marketing limit.

A small number of units do offer a 120/240 V output, and they sit in a different class: heavier, wired differently and usually fed by a transfer switch. If a 240 V load is the actual requirement, you are shopping for a home backup system, not a portable station.

A second hard limit is current per outlet. Continuous draw above about 1,440 W from a single 120 V socket is already at the edge of what the wiring wants to see for hours at a time, because a 15 A circuit allows 80% of its rating for a continuous load. Large loads should be spread across outlets.

Count the outlets before you count the watts. Most units in the overnight tier offer four to six AC sockets, but they share one or two internal inverter channels, so the sockets are convenience rather than capacity. If two devices must run at once, check the combined continuous draw against the inverter rating, not against the number of sockets.

The cards below cover four tiers plus two edge cases. Check surge rating and transfer time on the listing, and the price there, because we do not print it.

Adding panels is the most common upgrade and the most commonly wasted purchase. Every unit has a maximum solar input, usually between 200 W and 500 W on the tiers above. Panels beyond that cap do not charge the battery faster; they simply cannot be accepted.

Use the cap, not the panel count, when planning. A 1,024 Wh unit that accepts 400 W of solar needs about six hours of good sun to refill once you allow 85% efficiency. That is a full day of decent weather, which is why solar and a battery are a pair rather than a substitute for each other.

Read the first row against the second. Doubling the accepted input halves the time, but it also usually doubles the panel cost, and the last row is only reachable on the largest units. For most households the honest answer is that solar tops the battery up over a day, not that it makes the battery unnecessary.

A gas generator wins on stored energy per dollar and runs indefinitely while fuel lasts. A battery station wins on running indoors, no exhaust, no fuel storage, instant start and silent operation. The deciding question is not which is better but whether the load is long or short.

For a two-day outage running a fridge and lights, a battery station is simpler to live with in a house and needs no maintenance. For a week-long outage in winter, a generator with fuel is the only thing that scales. Many households end up with a battery for the short events and nothing for the long ones, which is a reasonable place to stop.

A third option sits between the two: panels on a balcony or in a yard that feed a wall outlet through a microinverter, with no battery at all. It only pays off if your utility credits the export, and the plug-in solar panel comparison covers which units are actually sold in the US and how their certification claims differ.

The comparison that matters is outages per year against hours per outage. Frequent short events favor a battery. Rare long events favor fuel, or a plan to leave.

Two practical points usually decide it. Fuel has a shelf life and needs rotating, and a generator cannot run indoors or in a garage because of carbon monoxide. A battery has neither problem but cannot be refilled. If the honest answer is that you want the fridge to survive an evening, the battery is the simpler purchase and the generator is a maintenance hobby you do not need.

Buying on capacity alone. A large battery behind a small inverter cannot start a compressor, and the listing rarely makes that obvious.

Reading power lifting as surge. Boost ratings describe resistive loads. A motor will not start on them.

Sizing to the average instead of the peak. Overnight energy is the easy part; the moment everything starts at once is the hard part.

Forgetting the transfer time. A fridge will restart on its own after a short gap. A desktop, a NAS or a modem will not survive even a brief cut unless the unit switches in milliseconds.

Buying panels and a station without checking the input cap. Extra panels beyond the accepted wattage are decoration.

The list above covers one unit per tier. These six fill gaps inside the same tiers, and each is separated from its neighbors by a single specification rather than by brand preference. Read the right-hand column before the product name.

• Jackery Explorer 300 — the smallest capacity here; its limit is the 300 W continuous output, not the 292 Wh.
• Anker SOLIX C1000, previous generation — 1,056 Wh at 1,800 W; the newer version adds output, not capacity.
• EcoFlow DELTA 3 Plus — same 1,024 Wh base as the DELTA 3, expandable to 2,048 Wh; the extra cost buys expansion.
• EcoFlow DELTA 3 Max — 2,048 Wh at 2,400 W; a middle step that exists for people who need two days but not 3 kWh.
• EcoFlow DELTA 3 Max Plus — the same battery with 3,000 W continuous, which is the number that matters for a window air conditioner.
• EcoFlow DELTA 3 Ultra Plus — 3,072 Wh and a surge rating that covers most single-motor starts.

Notice the pattern: capacity repeats in pairs, and what changes inside a pair is continuous output. That is the specification to compare when two units look identical on a shelf.

No unit was tested here. Specs come from listings and maker pages; the tier assignment comes from the arithmetic above. This page is not electrical advice and it is not legal advice. Storage batteries, transfer equipment and any hardwired connection are regulated, rules differ by state and by city, and they change. Have a licensed electrician review anything beyond a plug, and keep these units out of unheated spaces in freezing weather, because charging below freezing damages lithium cells.

Know your backup load already? The power station match calculator gives the size instead of a ranking.

Weighing a kit instead? See the two-route comparison.

Cell chemistry matters less than capacity: see LiFePO4 versus NMC.