Product Review · Updated November 2026
EcoFlow Smart Generator 4000 Review: Automatic Outage Backup for the Delta Pro 3 (vs Anker 5500)
The EcoFlow Smart Generator 4000 (Dual Fuel) is a gasoline or propane generator built to recharge an EcoFlow DELTA Pro 3 through a 3,200W DC cable, and to start itself when the battery runs low. For a Delta Pro 3 owner who wants outage backup that keeps going after the battery is drained, it is the simplest add-on. Currently $1,259.00 on Amazon, it costs less than Anker's tri fuel SOLIX Smart Generator 5500, which is the better match if you own an Anker SOLIX E10.
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By Morgan Chen
Reviewed & approved by Juhi Sahni
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Published: November 7, 2026
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Updated:
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Editorial Standards
DC Charging
3,200
Watts into a DELTA Pro 3
AC Rated
3,200
Watts gas · 2,900W propane
Weight
83 lb
Dual fuel (gas / LPG)
Price
$1,259.00
Current on Amazon
SGA score: 77/100 (smart-generator rubric below).
In California? Read the California restriction before you order.
Quick Verdict: Which Smart Generator Should You Buy?
EcoFlow Smart Generator 4000 · 77/100
Pick it if you own a DELTA Pro 3. It plugs straight into the battery's DC input, charges at up to 3,200W and starts on its own when the battery falls to a level you set. Gasoline or propane.
Anker SOLIX Smart Generator 5500 · 83/100
Pick it if you own (or plan to buy) an Anker SOLIX E10. It adds natural gas as a third fuel, up to 4,500W of DC charging and a NEMA 3R weatherproof enclosure. F3800 Plus and F3000 owners get AC pass-through, not direct DC charging.
The Anker scores higher in our scoring because it has more output, a third fuel and better published fuel efficiency. The score matters less than which battery you own, though. Neither generator charges the other brand's power stations over DC. If you don't own either battery yet, start with our EcoFlow Delta Pro 3 review or Anker SOLIX E10 review.
What Is the EcoFlow Smart Generator?
The EcoFlow Smart Generator 4000 (Dual Fuel), model EFSG4000-US-EPA, is a 196cc four-stroke generator that EcoFlow sells mainly as a battery charger. Its Amazon listing leads with "3200W DC fast charging" into the DELTA Pro 3. Instead of you running extension cords from a generator to the house, the generator feeds the battery, and the battery powers your home through its own outlets, a transfer switch or EcoFlow's Smart Home Panel 2.
The "smart" part is control. The listing describes four automatic start modes: a custom start, a night-care mode, a PV-priority mode that lets solar go first, and smart reverse charging, which starts the engine when the DELTA Pro 3 battery drops. Retailer guides describe setting a low and high battery threshold in the EcoFlow app: the generator starts at the low mark and shuts off at the high mark. The app also shows CO concentration, temperature, oil and overload alerts, and EcoFlow says all of them except fuel alerts trigger an automatic shutdown.
EcoFlow's Amazon listing says it is compatible with the DELTA Pro 3 and the original DELTA Pro after a firmware update. One retailer guide says the original DELTA Pro also needs a separate adapter cable, so confirm that with EcoFlow before ordering for an older unit. The listing names no other EcoFlow stations. Our EcoFlow power station guide covers the rest of the lineup.
EcoFlow Smart Generator 4000 vs Anker SOLIX Smart Generator 5500: Specs
Figures come from each maker's Amazon listing, product page or manual, cross-checked against retailer spec sheets. Where sources disagree, both figures are shown with attribution.
| Spec | EcoFlow Smart Generator 4000 | Anker SOLIX Smart Generator 5500 |
|---|---|---|
| Price | $1,259.00 | Check price at Amazon → |
| SGA score | 77/100 | 83/100 |
| Fuels | Gasoline, propane (LPG) | Gasoline, propane, natural gas |
| DC charging output | 3,200W at 40–60V (XT150) | Up to 4,500W (Turbo); 4kW Eco; output up to 400V |
| AC rated (running) output | 3,200W gasoline / 2,900W propane, 120V | 3,600W, 120V |
| Peak / starting | 3,500W (EcoFlow manual spec table) or 4,000W "with X-Boost" (retailer listings) | 5,500W (Amazon listing; Anker FAQ says 5,500VA); Anker's spec table lists 4,500W gas/propane, 4,000W natural gas |
| Energy per fuel load (maker figures) | 8 kWh per 1.59 gal gasoline tank; up to 24 kWh per 20-lb propane tank | 17 kWh per 2.64 gal (10 L) gasoline tank; propane figure not published |
| Runtime (maker figure) | 8 h at 25% load per gasoline tank | Not published as hours |
| Noise (published) | 70 dB at 7 m (23 ft), full load | 69 dB(A) at 23 ft, Eco mode |
| Weight | 83 lb | 110 lb (Anker) |
| Auto start | On DELTA Pro 3 battery level, plus night-care, PV-priority and custom modes | Auto start by battery state of charge; scheduled start |
| CO safety | App CO alert with automatic shutdown | CO alert and CO protection (automatic shutdown) |
| Weather | No enclosure rating published | NEMA 3R; −4°F to 131°F |
| Works with | DELTA Pro 3, DELTA Pro (firmware update) | E10 (DC); F3000, F3800, F3800 Plus via AC |
| California | Retailers: not CARB-approved, cannot ship to CA | Amazon listing: "not available in CA" |
| Warranty | 3 years (listing) | 3 years (listing) |
About the conflicting AC figures: EcoFlow's user manual (V1.2) and retailer spec sheets agree on a rated 3,200W on gasoline and 2,900W on propane. The peak is where they disagree: the manual's spec table gives 3,500W, while retailers advertise "4,000W peak with X-Boost". Size your loads against the 3,200W rated figure, which every source agrees on. The two noise figures were taken under different conditions (full load vs Eco mode), so they are not a like-for-like comparison.
Pairing the EcoFlow Smart Generator With the Delta Pro 3
This is the setup EcoFlow designed the generator around. The DELTA Pro 3 (4,096 Wh, 4,000W, 95/100 in our scoring) runs the house, and the Smart Generator refills it over DC instead of through the AC charger. EcoFlow's listing claims it "saves 40% of fuel" when fully charging the DELTA Pro 3, without stating the baseline in the listing. That is EcoFlow's own figure, and we have not seen an independent measurement of it.
How an automatic outage cycle works
- The grid goes down. The DELTA Pro 3 (or a Smart Home Panel 2) takes over your circuits on battery.
- When the battery falls to the low threshold you set in the EcoFlow app, the generator starts on its own.
- It charges the battery over the DC cable while the battery keeps powering the house.
- At your high threshold it shuts down, and the house runs quietly on battery again until the next cycle.
Runtime math: how far a tank goes
Estimates use EcoFlow's published energy figures and about 85% of the DELTA Pro 3's rated capacity as usable (4,096 Wh × 0.85 ≈ 3,482 Wh). Real results will be lower in cold weather and with heavy surge loads.
| Average home load | Battery alone | + one gas tank (8 kWh) | + one 20-lb propane tank (24 kWh) |
|---|---|---|---|
| 300W (fridge, router, lights) | ~11.6 h | ~+27 h | ~+80 h |
| 500W (+ freezer, CPAP, fans) | ~7 h | ~+16 h | ~+48 h |
| 1,000W (+ well pump, microwave use) | ~3.5 h | ~+8 h | ~+24 h |
Battery alone = 3,482 Wh ÷ load. Added hours = maker kWh figure ÷ load, before charging losses, so treat the generator columns as best-case upper bounds. At 3,200W, refilling those 3,482 usable Wh takes a little over an hour of engine time, before charge taper near full.
For whole-home wiring, the DELTA Pro 3 connects to your panel through a transfer switch, an interlock kit or the Smart Home Panel 2. Our transfer switch guide for solar generators explains the options, and our smart home panel guide compares EcoFlow's panel with Anker's and Jackery's. For the full parts list around one or two units, including the 50 Amp Hub and extra batteries, see our EcoFlow Delta Pro 3 home backup setup guide.
Anker SOLIX Smart Generator 5500: E10, F3800 Plus and F3000
Anker's generator is bigger and more expensive. Its listing gives 5,500W starting power, up to 4,500W of DC output for battery charging or 3,600W of AC to run appliances directly, and three fuels: gasoline, propane or natural gas. The enclosure is NEMA 3R weatherproof, and Anker rates it for −4°F to 131°F.
The important detail is which Anker station gets what. The DC connection is built for the Anker SOLIX E10, through a dedicated cable that carries both power and control signals. Anker's own integration guide says the generator's output runs up to 400V, so it cannot be connected directly to the F3800 Plus or F3000, which Anker calls low-voltage portable stations. Those stations can still control the generator's automatic start/stop.
| Anker station | How it connects (Anker guide) | Auto start/stop |
|---|---|---|
| SOLIX E10 | DC coupling by dedicated cable, up to 4,500W | Yes, by battery state of charge |
| SOLIX F3800 Plus | 120V / 1,800W AC pass-through; an AC charging cable (1,800W) and generator adapter (3,000W) are listed for Q4 2026 | Yes (Anker guide) |
| SOLIX F3000 | 120V / 3,600W AC pass-through | Yes (Anker guide) |
| SOLIX F3800 | 120V / 1,800W AC pass-through; charging input listed for Q1 2027 | Not stated |
Anker's guide notes that "product features and delivery timelines may change". Check the current status before buying the generator for an F-series station.
In practice, an F3800 Plus owner today gets generator power passed through to the house at 1,800W, not the 4,500W DC fast charge that E10 owners get. An F3000 owner gets 3,600W of pass-through, so the generator carries the house load without draining the F3000's battery. That still adds up to a longer outage, but it isn't the same as the EcoFlow and DELTA Pro 3 arrangement, where the generator refills the battery directly.
Smart Generator vs Inverter Generator
An inverter generator such as the Westinghouse iGen5000DFc from our best inverter generator picks powers appliances directly through its own outlets, and it works with any brand of power station that has an AC input. A smart generator is built to charge a battery, and its best features only work with one brand's batteries.
A smart generator makes sense if you...
- ✓ Already own a DELTA Pro 3 or SOLIX E10 and want outages longer than the battery can cover alone.
- ✓ Want the engine to start and stop by itself, including overnight.
- ✓ Want short engine run times instead of a generator running all day at light load.
- ✓ Have propane (or, for the Anker, natural gas) and want to avoid storing gasoline.
Buy a regular inverter or propane generator if you...
- ✗ Own a Jackery, Bluetti or older EcoFlow station. These smart features won't work with them.
- ✗ Want 240V or 30A/50A outlets for a transfer switch with no battery in between. Our best propane generator picks cover that.
- ✗ Want a light generator for camping. At 83 to 110 lb, these are not one.
- ✗ Live in California (see below).
If you are still deciding between a battery system and a fuel generator in the first place, our solar generator vs gas generator comparison covers cost, noise and maintenance. Note that the smart generators here are scored on their own rubric (below), so their scores aren't directly comparable with our inverter generator scores.
California: Neither Smart Generator Is Sold There
- Anker SOLIX Smart Generator 5500: the Amazon listing states "Smart Generator not available in CA" and points California buyers to the E10 battery and solar instead.
- EcoFlow Smart Generator 4000: EcoFlow's Amazon listing does not mention California. The model is the EPA version (EFSG4000-US-EPA), and authorized retailers including Solartown and Outbound Power list it as not CARB-approved and not shippable to California. We could not load EcoFlow's own product page to confirm, and one retailer has claimed it can ship there, so California buyers should get written confirmation from EcoFlow before ordering.
Neither maker claims CARB certification for these models. We have not listed any certification beyond what the makers state: EcoFlow's manual includes an EPA emissions control warranty, and Anker's spec table lists EPA conformity. California readers who need outage backup should look at battery-only systems. Our home battery backup guide covers options that need no fuel.
Safety: Carbon Monoxide Rules Still Apply
Both of these generators burn gasoline or propane, and both produce carbon monoxide. Auto start makes this more important, because the engine can start in the middle of the night without anyone watching. According to the CPSC, an average of nearly 100 people in the U.S. die each year from CO poisoning caused by portable generators.
- Outdoors only, at least 20 feet from the house. CPSC: "Operate portable generators outside only, at least 20 feet away from the house." The CDC says to keep a generator at least 20 feet from any doors, windows or vents.
- Never in a garage, basement, crawlspace or shed, even with the door open (CPSC). Point the exhaust away from the house.
- Install CO alarms. The built-in CO shutoff protects the area around the generator, not the inside of your house. Anker's own page says its CO sensor is not a substitute for indoor CO detectors. Put battery-backed alarms on every level. See our best portable carbon monoxide detector picks.
- Keep it dry without enclosing it. The Anker carries a NEMA 3R rating. EcoFlow publishes no enclosure rating, so in rain or snow use a vented generator cover made for running units. Our best generator tent guide explains the options. A cover doesn't change the 20-foot rule.
If you need a placement plan for a winter outage, our winter storm power backup guide walks through it step by step.
EcoFlow Smart Generator 3000 vs 4000
EcoFlow also makes a smaller Smart Generator 3000 (Dual Fuel), model EFSG3000-US-EPA. Retailer listings such as HVACDirect describe it as rated 2,000W on gasoline and 1,800W on propane with a 3,000W peak, roughly 48 lb, and pairing with the Delta 3 series. We could only confirm those figures from retailer listings, not from EcoFlow, and they disagree on its warranty. We also could not find it on Amazon, so we don't link or score it here.
The simple rule is that the 4000 is the one that pairs with the DELTA Pro 3 and original DELTA Pro over DC. If you own a smaller Delta 3 model, check EcoFlow's compatibility list for the 3000 before buying. Our which EcoFlow Delta should I buy guide explains the differences between the stations.
EcoFlow Smart Generator 4000: Pros & Cons
Pros
- ✓ 3,200W DC charging straight into a DELTA Pro 3
- ✓ Starts automatically on low battery, with night-care and PV-priority modes
- ✓ Gasoline or propane; EcoFlow lists up to 24 kWh from a 20-lb tank
- ✓ App CO, temperature, oil and overload alerts with automatic shutdown
- ✓ Lower price than the Anker 5500
- ✓ 3-year warranty (listing)
Cons
- ✗ Smart features only work with the DELTA Pro 3 and DELTA Pro
- ✗ Retailers say it is not CARB-approved and cannot ship to California
- ✗ 70 dB at 7 m at full load: an engine, not a battery
- ✗ 83 lb, with no published enclosure (weather) rating
- ✗ No natural gas option (the Anker has one)
- ✗ Peak AC figure differs between sources (3,500W vs 4,000W)
How We Score Smart Generators
Our scores are calculated from published specs, the maker's own figures and current Amazon prices. We have not run these generators ourselves. Each dimension is scored 0–90. A spec that isn't published is left out and its weight is shared across the other dimensions; it never counts as zero.
| Dimension (weight) | How it's scored | EcoFlow 4000 | Anker 5500 |
|---|---|---|---|
| Output (25%) | Average of AC-running and DC-charging scores, on the same watt scale as our gas generators | 77.0 | 86.0 |
| Fuel flexibility (15%) | Tri fuel 90, dual 80, gas only 40 | 80 | 90 |
| Station integration (20%) | Direct DC into a same-brand station 40 + auto start on battery level 30 + app control and alerts 20 | 90 | 90 |
| Runtime per fuel (15%) | Maker kWh per gallon of gasoline vs the best (Anker 6.44, EcoFlow 5.03) | 70.3 | 90 |
| Noise (10%) | 90 − 2.5 × (published dB − 52); both published at 7 m | 45.0 | 47.5 |
| Value & warranty (15%) | 70% price per continuous watt vs the lowest, 30% warranty (3 years = 80) | 87.0 | 79.8 |
| SGA score | Weighted total, rounded | 77 | 83 |
Value uses Amazon prices on November 7, 2026, so it can shift as prices change. Full method: Editorial Standards.
Bottom Line
If you own a DELTA Pro 3 and live outside California, the EcoFlow Smart Generator 4000 is the natural way to make its outage backup last longer.
It charges the battery directly over DC, starts itself when the battery runs low and can run on propane instead of stored gasoline. At $1,259.00 on Amazon, it costs less than Anker's 5500, which is the stronger generator on paper but delivers its DC fast charging only to the E10. Whichever you choose, run it 20 feet from the house and keep CO alarms inside.
Sources & Data Verification
Specs are cross-referenced between each maker's Amazon listing, product page or manual and independent retailer spec sheets. Fuel, runtime and efficiency figures are the makers' published claims. Learn more on our Editorial Standards page.
- • EcoFlow — Smart Generator 4000 (Dual Fuel) Amazon listing (features and compatibility), accessed November 7, 2026
- • EcoFlow — Smart Generator 4000 user manual V1.2 (rated power, tank, weight, dimensions)
- • Mighty Generators — Smart Generator 4000 overview (DC voltage, noise, auto-start thresholds, California)
- • Solartown — EFSG4000-US-EPA spec listing
- • Anker — SOLIX Smart Generator 5500 product page and Amazon listing
- • Anker — Smart Generator 5500 integration guide with portable power stations
- • CPSC — Winter weather safety tips: fires and carbon monoxide
- • CDC — Use a generator safely
Frequently Asked Questions
Does the EcoFlow Smart Generator work with the Delta Pro 3?
Yes. The DELTA Pro 3 is the main station it is designed for. It charges the battery over DC at up to 3,200W and can start automatically when the battery drops to a level you set in the EcoFlow app. EcoFlow's listing also names the original DELTA Pro after a firmware update; one retailer says that older model needs an adapter cable.
Can I buy the EcoFlow or Anker smart generator in California?
Anker's Amazon listing says the Smart Generator 5500 is not available in California. For the EcoFlow Smart Generator 4000, authorized retailers list it as not CARB-approved and not shippable to California. EcoFlow's Amazon listing doesn't address it, so California buyers should confirm with EcoFlow before ordering.
How much fuel does the EcoFlow Smart Generator use?
EcoFlow says one 1.59-gallon gasoline tank produces about 8 kWh, or 8 hours at 25% load, and a 20-lb propane tank produces up to 24 kWh. That 24 kWh is nearly seven refills of a DELTA Pro 3's usable capacity (about 3,480 Wh) from empty, before charging losses. These are maker figures, and real fuel use depends on load and temperature.
What is the difference between a smart generator and an inverter generator?
An inverter generator powers appliances through its own outlets and works with any power station that has an AC input. A smart generator is designed to charge a specific brand's battery, often over DC, and to start and stop itself based on that battery's charge level. Smart generators make sense if you already own a DELTA Pro 3 or Anker E10; otherwise a regular inverter or propane generator is more flexible.
Can the Anker SOLIX Smart Generator 5500 charge an F3800 Plus or F3000?
Not directly. Anker says the generator's output reaches 400V, so it cannot connect directly to the F3800 Plus or F3000. Those stations use 120V AC pass-through instead (1,800W for the F3800 Plus, 3,600W for the F3000), and they can still control the generator's auto start/stop. Anker lists an AC charging cable for the F3800 Plus for Q4 2026 and says timelines may change. Direct DC charging at up to 4,500W is for the SOLIX E10.
Is it safe to run a smart generator in my garage?
No. CPSC says never to run a portable generator inside a home, garage, basement, crawlspace or shed, and to run it outside at least 20 feet from the house. CDC guidance is to keep it at least 20 feet from doors, windows and vents. A built-in CO shutoff does not replace battery-backed CO alarms inside the home.