Power Station Specs Explained: Wh, Watts, Surge, and the Numbers That Lie

The Spec Sheet Is the Product

A portable power station is four numbers in a box: how much energy it stores, how fast it can release it, how fast it can absorb it, and how many times it can do that before the battery wears out. Everything else — the app, the light bar, the cupholder-grade accessories — is trim. This guide defines every number that matters, in the order they should drive your decision, and flags the places where spec sheets are technically true but practically misleading.

Watt-Hours (Wh): How Much Energy It Stores

Watt-hours are the gas tank. One watt-hour runs a 1-watt load for one hour; a 1,024Wh unit like the EcoFlow DELTA 2 stores enough energy to run a 100W load for roughly 10 hours — before losses, which we'll get to.

The classes break down roughly like this:

Class	Capacity	Typical job
Compact	245–300Wh	Phones, laptops, lights, CPAP for a night
Mid	~500Wh	The above, for longer — a tweener class
Workhorse	1,000–1,200Wh	Refrigerator for a day, remote work, car camping
Backup	2,000Wh+	Multi-day essentials, power tools, off-grid living

Where the number lies: capacity is quoted at the battery, not the outlet. Converting DC battery power to AC wall power burns energy in the inverter — typically around 15%. A realistic planning figure for AC loads is capacity × 0.85. That 1,024Wh unit delivers roughly 870Wh to your appliances. Spec sheets never print the derated figure; you should never plan without it.

Watts (W): What It Can Run

Continuous AC output — the inverter rating — is the bouncer at the door. A unit with a 300W inverter will not run a 900W microwave for even one second, no matter how many watt-hours sit behind it. This is the single most common first-time buyer error: paying for capacity while the inverter quietly limits the unit to electronics.

Rough draw figures worth memorizing: laptops 30–100W, full-size refrigerators 100–200W running, microwaves 600–1,500W, coffee makers 800–1,400W, space heaters 1,500W, power tools 500–1,800W. Match the inverter to the single biggest load you'll ever plug in — check specific appliances in our can-it-run database — then check capacity for duration.

Surge Watts: The Startup Tax

Anything with a motor or compressor — refrigerators, pumps, air conditioners, many tools — briefly draws 2–3x its running wattage at startup. Surge rating is the inverter's ability to absorb that spike, usually for under a second.

This is where similar-looking units split. The EcoFlow DELTA 3 Plus and the DELTA 2 share a 1,800W continuous inverter, but surge at 3,600W and 2,700W respectively. Both run a refrigerator; the 3 Plus has 33% more margin to start a stubborn one on a hot day, when compressors pull hardest. A surge failure doesn't look dramatic — the unit just faults and your fridge stays off. Audit the startup draw of every motor on your list, not just the running draw.

Marketing Watts: X-Boost and Friends

Several manufacturers ship modes — EcoFlow calls theirs X-Boost — that claim to run appliances rated above the inverter's continuous output. The mechanism is voltage reduction: the unit lowers output voltage so a resistive load draws fewer watts than its label says.

Know exactly what this is and isn't. For purely resistive loads — kettles, heaters, some hot plates — it genuinely works: the device runs, just cooler or slower than on wall power. For motors, compressors, and most electronics with power supplies, undervolting ranges from "won't work" to "actively harmful." Treat boost modes as a convenience for heating elements, never as a substitute for buying the right inverter. When you compare units, compare the honest continuous-watt number — that's the figure our ratings use, as documented in our methodology.

Runtime: The Formula That Replaces Label Math

Vendor runtime claims ("powers your fridge for 30 hours!") are usually built on best-case duty cycles they don't disclose. Here's the model we use across every rating on this site:

Runtime (hours) = Wh × 0.85 ÷ (device watts × duty cycle)

The 0.85 covers inverter losses. Duty cycle is the fraction of time the device actually draws power: a refrigerator compressor runs roughly a third of the time (duty ≈ 0.33), a CPAP runs constantly (1.0), a microwave runs minutes at a time (irrelevant duty — check inverter watts instead).

Worked example — 150W refrigerator at 0.33 duty on a 1,024Wh unit: 1,024 × 0.85 ÷ (150 × 0.33) ≈ 17.6 hours. The label-math answer (1,024 ÷ 150 = 6.8 hours) is wrong in the pessimistic direction here; for constant loads, label math is wrong in the optimistic direction by the 15% inverter loss. Either way it's wrong. Run your actual devices through the runtime calculator — it applies this model automatically.

Battery Chemistry: The Lifespan Spec

Two chemistries dominate: LiFePO4 (LFP) and NMC. The difference is cycle life — how many full charge-discharge cycles before the pack degrades to 80% of original capacity:

• LFP: roughly 3,000+ cycles. Daily use for 8+ years.
• NMC: roughly 500–800 cycles. Daily use for under two years.

NMC's advantage is energy density (lighter per Wh), which is why it survives in a couple of weight-focused compact units. But 12 of the 14 units in our current database are LFP, and at equal prices there is no good reason to accept the 4–6x shorter-lived chemistry. If a spec sheet says only "lithium-ion" without specifying, assume NMC and price accordingly.

Charge Specs: Wall and Solar

Modern spec sheets quote charging as time to 80% — because charging slows dramatically for the final 20% to protect the battery, and 0–100% times look worse. The current field ranges from 30 minutes (EcoFlow RIVER 3) to 102 minutes (Jackery Explorer 2000 Plus) to 80%. Fast wall charging matters more than it seems: it's what makes "charge during the storm warning" and "top up over lunch" workable strategies.

Solar input is quoted as a maximum wattage the unit will accept — 100W on compact units, up to 2,600W on the EcoFlow DELTA Pro 3. Two caveats. First, the ceiling is a limit, not a promise: you supply the panels, and real-world panel output runs 70–85% of panel rating in good sun. Second, the ceiling determines whether off-grid daily cycling is viable: a 2,000Wh unit with a 1,000W ceiling needs roughly 2.5–3 hours of strong sun for a full refill. If solar is central to your plan, the input ceiling belongs near the top of your spec checklist.

Weight: The Spec You Feel Every Time

Watt-hours are heavy. LFP units run roughly 35–40Wh per pound at the pack level: ~7.8 lbs at 245Wh (EcoFlow RIVER 3), ~27 lbs at 1,024Wh, ~61.5 lbs at 2,042Wh (Jackery Explorer 2000 Plus), 113.5 lbs at 4,096Wh. There is no trick that avoids this — only the decision about how much you're willing to carry. Buy capacity for your loads, not for hypotheticals, because unused watt-hours are pure dead weight.

Reading a Spec Sheet in 30 Seconds

In order:

1. Continuous watts ≥ your single biggest load. Disqualify everything that fails.
2. Surge watts ≥ 2–3x your biggest motor load. Disqualify the marginal.
3. Chemistry = LFP, unless you have a weight-driven exception and a discount.
4. Watt-hours × 0.85 ÷ your load profile ≥ the runtime you need.
5. Charge specs match your recharge plan — wall speed for backup duty, solar ceiling for off-grid.
6. Weight you can actually move along the path it'll travel.

Every rating on this site is built from those six numbers. The full scoring weights are in our methodology — and once you can read a spec sheet this way, you'll notice how much of the category's marketing is engineered to keep you from doing exactly that.

FAQ

Why do two units with the same watt-hours have different runtimes?

Inverter efficiency varies a few points between units and across load levels — inverters are least efficient at very small loads — and vendor runtime claims assume different duty cycles. Spec-sheet capacity is the battery's rating, not delivered AC energy. The 0.85 derate is a sound planning average; treat anything beyond ±10% of the modeled figure as a reason to re-check the device's real draw.

Is a higher surge rating ever a bad thing?

No — surge headroom is pure margin and costs you nothing in operation. It correlates with bigger inverter hardware, which adds some weight and cost, but between two otherwise similar units the higher surge rating is strictly the safer buy.

Do watt-hours on the box include the inverter loss?

No. Quoted Wh is battery capacity measured at the cells. Energy delivered through the AC outlets is roughly 85% of that; DC outputs (USB-C, 12V) lose less, typically in the 90–95% range. Plan AC loads at capacity × 0.85.

What's the single most important spec?

Continuous inverter watts — because it's binary. Too few watt-hours means less runtime; too few watts means the device doesn't turn on at all. Size the inverter to your biggest load first, then buy as many watt-hours as your runtime math and your back can justify.