What the advertised 3600 Wh are really worth
The Delta Pro carries a 3600 Wh LiFePO4 battery, rated for 6500 cycles before dropping to 50 % of its original capacity. In one reading, 3291 Wh are actually delivered at the AC output, or 91 % of the rated value. In a second reading, carried out on another continent with a different protocol, the order of magnitude remains consistent, around 85 %. The two measurements do not follow the exact same protocol, so they do not compare down to the last digit, but they converge on a solid range for this type of product.
The 6500-cycle figure remains a manufacturer datapoint, repeated consistently across many sites but never reproduced by an independent lab to date. The best-batteries.com editorial team has owned and used this unit since October 2021, with no sign of weakness to date, a long, first-hand track record on how well the cell holds up over time. An independent usage report after two years of daily use reaches the same conclusion, with no perceptible capacity loss. Both positive signals concern the battery cell itself, to be distinguished from the isolated incidents covered further below, which concern the switching electronics rather than the battery.
A history of backup-mode failures worth knowing about
The Delta Pro includes a UPS function (uninterruptible power supply), which automatically switches to battery power in the event of a mains outage. It is precisely in this mode, called EPS at EcoFlow, that a set of serious failures was documented in 2022: cracking sounds, flashing, smoke, with an error code 121 identified on several separate units. The cause was acknowledged by EcoFlow (a fault during inverter switching in EPS mode) and corrected by a firmware update released in July 2022.
A more recent and separate incident is documented on the German market: a jet of flame from the ventilation grilles on a unit used alongside an induction hob, after repeated use in partial discharge. The case was referred to the relevant local authorities, with no public conclusion available to date; the leading theory points to an inverter component rather than the battery itself.
Recharging, a genuine measured strength
On this point, the Delta Pro does better than its own spec sheet. The often-cited figure of 2.7 hours actually applies to the American market (1800 W at 120 V); for Europe, EcoFlow states around 1.9 hours at 2900 W. A full charge is measured at 98 minutes with 2680 W actually delivered, faster than the European claim itself.
The MultiCharge function, which combines mains, solar and generator input to reach up to an advertised 6500 W, has not, on the other hand, been the subject of any isolated independent measurement found to date: this combined figure remains an uncorroborated manufacturer datapoint.
Expandable to 25 kWh, on paper
The central argument for the Delta Pro remains its expandable ecosystem: adding extra batteries and pairing two units via a Smart Home Panel takes the advertised capacity up to 25 kWh. Over two years of use with this configuration (two units and a Smart Home Panel), the balance sheet remains positive, with a warranty replacement obtained in under two weeks following one incident.
A bug causing uneven charge distribution between the main unit and the additional batteries has also been documented (one concrete case: one unit at 1.5 % charge while an additional battery stayed at 60 %), partially fixed by a firmware update in late 2022 with no confirmation that it was fully resolved.
A more concrete problem today: the extension battery dedicated to this model is itself out of stock directly at EcoFlow at the time of writing. The expandability argument, however real on paper, becomes hard to put into practice for a new buyer as long as this part remains unavailable.
Can you still buy it new today?
This is the most important question to ask before anything else. The original Delta Pro has almost entirely disappeared from the new-unit retail circuit in France. The official EcoFlow site shows it as out of stock, with only an email alert form in place of the buy button. The three major general retailers checked no longer list it at all; only its successor, the Delta Pro 3, now appears on their shelves.
The rare stock still visible is found on marketplaces, at prices well above the catalog price of 1699 €, up to more than double. A French buyer publicly reported this gap in early 2026, after discovering the far lower official price once the purchase had already been made elsewhere.
The secondhand market, a more realistic alternative
Unlike the new market, the secondhand market between private individuals in France remains active and reasonably priced, without the overpricing seen on professional marketplaces: units commonly change hands between 1200 and 1850 €, accessories and linking cables included in some listings. For anyone who accepts a reduced or absent warranty, this is today the most realistic way to get this model at a price consistent with its original positioning.
Brand reliability and after-sales service
At the brand level rather than the product alone, EcoFlow shows an overall rating of 3.6 out of 5 on Trustpilot France, across its whole range, with a response given to around a third of negative reviews within an average of one month. A recurring failure required several exchanges over four months before resolution, in one documented case. Conversely, a warranty replacement was obtained in under two weeks in another documented case. The signal remains mixed, consistent with a large general-purpose brand rather than a specific black mark against this product.
Against its successor, the Delta Pro 3
The Delta Pro 3 has taken over as the flagship model in EcoFlow's high-capacity lineup, at a notably higher price (3299 € confirmed across five independent sources at the time of writing) for a higher base capacity (4096 Wh) and greater power. The original Delta Pro keeps an advantage on paper with a wider advertised expandability (25 kWh versus 12 kWh) and a higher advertised cycle count, but both arguments matter less as long as new units remain hard to find and its own extension battery stays unavailable.
Who it's for
The Delta Pro suits anyone who can still find it at catalog price from a reliable retailer, or who accepts the secondhand market in exchange for a consistent price: in that case, it is a solid energy base, with decent measured efficiency and mains recharging that beats its own claim. Particular vigilance is recommended for automatic backup-mode use, with the firmware kept up to date.
It does not suit anyone who needs an immediate new purchase at the listed price: current availability makes that goal unrealistic in France, and the Delta Pro 3 or another in-stock reference remain the more direct choice for that scenario.
