The box on a 4,096Wh power station says it’ll run your cabin “for days.” Plug in a mini fridge, a string of LED lights, a CPAP, and a Starlink dish on a 28°F October night, and by sunrise the display is often already down in the 30s — not because the battery lied about its watt-hours, but because the watt-hours printed on the box and the watt-hours you can actually pull out of a cold LiFePO4 pack through a real inverter are two different numbers, and nobody puts the second one on the packaging.
This isn’t a spec-sheet shootout. EcoFlow’s Delta Pro 3, Bluetti’s AC300, and Anker’s SOLIX F3800 all sit in the same 3–4kWh expandable tier built for exactly one job: running a cabin on solar and battery instead of the grid, whether that’s three weekends a month or three hundred and sixty-five days a year. Ranked by nameplate watt-hours and inverter wattage alone, the three look nearly interchangeable. Ranked by what actually gets you through a real cabin night — and what happens to each one when the thermometer drops — they stop looking interchangeable at all.
The Watt-Hour Number on the Box Isn’t the Number You Get
Every portable power station loses capacity in the same three places on the way from the battery cell to your fridge, and all three losses apply before the weather even gets involved.
- Depth-of-discharge reserve. LiFePO4 tolerates a near-full discharge better than any other common chemistry, but a cabin power station is also your only supply — running it down to the BMS’s hard cutoff mid-cycle means losing fridge power at 2 a.m., not a warranty claim. Budget on using about 90% of nameplate, not 100%.
- Inverter conversion loss. Every watt that leaves the battery as DC and reaches an AC outlet passes through an inverter that runs roughly 85–90% efficient under a real, moving load — not the single peak-efficiency figure on the spec sheet. That’s 10–15% gone to heat before it reaches the compressor.
- Standby draw. These three units pull roughly 15–40W just to keep the inverter section awake — cooling fans, display, standby electronics — any time AC output is switched on, whether or not a load is plugged in. Leave it live overnight for a fridge and that’s another 150–400Wh gone by morning that never shows up as a “load” on any spec sheet.
Key number
Multiply nameplate watt-hours by roughly 0.90 (usable reserve) × 0.88 (inverter efficiency) ≈ 0.79 and that’s the honest number to plan a cabin night around — about four-fifths of what’s printed on the box, before standby draw takes its own separate cut. A “4,096Wh” station is really closer to a 3,200Wh station once it’s wired to the cabin.
Three Stations, One Job: Sized for a Cabin
All three sit in the same class for a reason — base capacity in the 3–4kWh range, a real inverter rather than a glorified UPS, and a modular path to add more battery later. Here’s what’s actually different once they’re lined up.
| Station | Base nameplate | Continuous inverter | Charges down to | Expansion path |
|---|---|---|---|---|
| EcoFlow Delta Pro 3 | 4,096Wh | 4,000W | 32°F / 0°C | +4,096Wh per Smart Extra Battery |
| Bluetti AC300 | 3,072Wh (hub + 1×B300) | 3,000W | 32°F / 0°C, throttled near the floor | +3,072Wh per B300, up to 4 on one hub |
| Anker SOLIX F3800 | 3,840Wh | 6,000W | 32°F / 0°C | +~3,800Wh per expansion battery, deepest stacking of the three |
Specs current as of 2026 per manufacturer documentation; all three brands revise bundles and firmware limits periodically — confirm the current listing before you buy. Current pricing and region-matched buy links are further down this page.
How Each One Grows With the Cabin
The Delta Pro 3 doubles in one step: a single Smart Extra Battery takes it from 4,096Wh to 8,192Wh, and EcoFlow’s stacking continues from there for a cabin edging toward whole-home power. The AC300 is the most granular of the three — it’s sold as a hub plus a separate B300 battery, so you can start with one 3,072Wh module and bolt on up to three more later, buying exactly the capacity this year’s loads need instead of guessing three years out — the cheapest of the three to grow incrementally. The SOLIX F3800 has the highest ultimate ceiling of the three once you start stacking expansion batteries and additional units, backed by the only 240V-capable inverter of the three — the one to buy once the cabin’s loads include a well pump, a mini-split, or anything else that actually needs 240V, not just more hours of the same 120V draw.
Real Overnight Autonomy, Worked for an Actual Cabin
Take a genuinely efficient, propane-heated off-grid cabin — not a fantasy number:
- 12V compressor fridge/freezer: ≈1,200Wh/day
- LED lighting, evening hours: ≈150Wh/day
- Starlink Mini, daytime connectivity: ≈500Wh/day
- CPAP and device charging overnight: ≈150Wh/night
- Propane furnace blower and ignition: ≈200Wh/day
Total: ≈2,200Wh/day. Run that against each station’s real usable capacity (nameplate × 0.79 from the formula above) and the picture looks nothing like the marketing copy:
| Station | Real usable, base | Real days, base | +1 expansion battery | Real days, expanded |
|---|---|---|---|---|
| Delta Pro 3 | ≈3,240Wh | ≈1.5 days | 8,192Wh → ≈6,490Wh | ≈2.9 days |
| Bluetti AC300 | ≈2,430Wh | ≈1.1 days | 6,144Wh → ≈4,860Wh | ≈2.2 days |
| Anker SOLIX F3800 | ≈3,040Wh | ≈1.4 days | 7,680Wh → ≈6,070Wh | ≈2.8 days |
Worked example only — swap in your own daily load and these numbers move accordingly. Running different loads? The power-station sizing calculator plugs in your own list instead of this worked example.
Line these up against the marketing and the pattern is obvious: every base unit here promises to run a cabin “for days” and actually delivers about one real day before it needs sun, a generator, or the grid again. What separates these three isn’t the base unit at all — it’s how cheaply and how far each one expands once one day of autonomy stops being enough, and how reliably each one can actually recharge when it needs to. That second part depends on something the days-of-autonomy table can’t show you.
The Cold-Weather Problem No Spec Sheet Leads With
LiFePO4 handles cold better than almost any other lithium chemistry for one specific thing: discharging. All three of these units will run a fridge or a string of lights down to well below freezing without complaint. Charging is a completely different chemical process, and every one of these three restricts it hard near freezing — which matters enormously for a cabin, where the unit itself is often sitting in an unheated room waiting for tomorrow’s sun to do its job.
Charge vs. Discharge Isn’t the Same Spec
- EcoFlow Delta Pro 3: charges from 32°F/0°C up to 113°F/45°C — the widest charge window of the three, and it’ll accept at least some current right at the freezing line.
- Bluetti AC300: the same nominal 32°F/0°C floor on paper, but Bluetti’s own support documentation and user community both note charge current throttles hard as the internal pack nears that floor — and that a load running on the unit at the same time, which generates its own heat, measurably improves cold-charge acceptance.
- Anker SOLIX F3800: the same 32°F/0°C floor as the Delta Pro 3, per Anker’s own spec sheet, up to a 104°F/40°C ceiling — a narrower top end than the Delta Pro 3’s 113°F/45°C, but no worse at the cold end than either of the other two. Cold-morning charging isn’t what actually separates these three; base price and 240V capability are.
None of this means solar charging fails in a cold climate — panels themselves actually run more efficiently in cold, bright weather. It means the bottleneck usually isn’t the sun, it’s the battery pack’s own temperature, and a power station left in an uninsulated cabin corner over a hard freeze can sit at a stubbornly low state of charge no matter how bright Saturday morning is, until it warms back up on its own. The fix has nothing to do with wattage: keep the unit in the warmest room in the cabin, not the mudroom or an unheated shed, or plan on a generator or grid top-up on the coldest mornings instead of counting on solar to bail it out before noon.
Which One Fits Your Cabin
- Weekend cabin, cold shoulder seasons, nobody there mid-week: all three share the same 32°F/0°C charge floor on paper, so cold tolerance is a wash here — price and simplicity aren’t. The Delta Pro 3’s single-box design, with no separate battery module to track, suits an occasional-use cabin nobody’s optimizing dollar-per-kWh on.
- Cabin that’s slowly going full-time: the Bluetti AC300’s modular B300 batteries let you buy exactly the capacity this year’s loads need and bolt on more later without replacing the core unit — the best buy-small-grow-later economics of the three.
- Real 240V loads — a well pump, a mini-split, a table saw: the Anker SOLIX F3800’s 6,000W from a single box handles motor starts the other two need a second unit for, and its expansion batteries give it the highest ultimate ceiling of the three — worth it as long as the unit lives somewhere that stays above freezing through the cold months, same as the other two.
Current picks, priced for your region
All three ship with region-specific pricing, bundle options, and current promotions below — worth checking before you commit to a spec on paper.
Where a Power Station Stops Making Sense
Every recommendation above assumes the cabin’s real daily load stays somewhere around 2–3kWh — a fridge, lights, connectivity, and a furnace blower. Add a well pump, real electric heat, a workshop, or year-round occupancy, and the math that made a $1,500–3,000 power station the right call stops working: at that point you’re no longer buying portable battery capacity, you’re building a permanent off-grid power system with a proper inverter/charger, a fixed battery bank sized for the actual house, and a solar array to match — a different budget and a different design process entirely. If the cabin’s headed that direction, that’s worth a real load-by-load conversation before spending on a fourth expansion battery for a station that was never built to be the whole system.
Can I run one of these off solar panels alone, with no wall charging?
Yes — all three accept substantial direct solar input on the base unit (the Delta Pro 3 up to roughly 2,600W, the AC300 and F3800 up to roughly 2,400W each — none of them capped anywhere near 1,000W), and that’s the normal way to run a cabin day to day. The catch is the cold-charging floor above: panels producing plenty of watts on a clear cold morning still can’t push them into a pack that’s below its charge-temperature threshold, so solar-only works fine in mild weather and needs the pack kept warm through a hard freeze.
Do I need the biggest expansion battery I can afford?
Usually not on day one. Sizing to a realistic 2–3 day autonomy target for the loads you actually run today — not a worst-case “what if everything ran at once” number — keeps the system sized to the cabin instead of to anxiety. The Bluetti AC300’s modular B300 batteries make it cheapest to grow into more capacity later if the cabin’s use changes; the other two cost more to add capacity retroactively.
What actually kills a LiFePO4 power station fastest in a cabin?
Two habits, both avoidable: routinely draining it past the BMS’s low-voltage cutoff instead of recharging with margin left, and repeatedly forcing charge cycles while the pack is cold-soaked near or below freezing — exactly the scenario an unattended, locked-up cabin creates every winter weekend. Keeping a reserve and keeping the unit warm before charging solves both.
Is a 4kWh-class power station enough to fully replace a generator at a cabin?
For a weekend cabin with efficient, moderate loads and decent solar exposure, generally yes — that’s exactly the job this tier is built for. For a cabin used through winter with unreliable sun for days at a stretch, most owners still keep a small generator or a grid connection as the actual backup for the battery, the same way a whole-home battery system keeps a generator as backup rather than replacing it outright.