EcoFlow STREAM Ultra X and STREAM Ultra review (UK)

The STREAM Ultra X and STREAM Ultra are EcoFlow's balcony-scale batteries: a box that takes up to 2,000 W of solar panels on four inputs, stores what the house doesn't use, and feeds it back into your wiring in the evening. On 1 October 2026 EcoFlow UK had the Ultra X at £1,299 and the Ultra at £899. For the rest of the range, including the 5 kWh STREAM 5000, see our guide to every STREAM model.

STREAM Ultra X vs STREAM Ultra: the specs

EcoFlow's own FAQ names three differences: the Ultra X has twice the battery, charges faster, and has a different front case. The spec tables add the weight and size. Everything else matches:

Both use LFP cells and have no fans. EcoFlow lists 2,300 W as the most device power either supports; the sockets give 1,200 W and the feed into the house wiring is 800 W. Both were on sale below list price when we checked, and EcoFlow's pages carry a 30-day price guarantee.

Which one should you buy?

• The Ultra X if you want to cover most of a typical evening, or you're likely to add panels up to the full 2,000 W. At about £338 per kWh of storage against the Ultra's £468, it's the better buy per unit of battery.
• The Ultra if the evening load is small, the budget is tight, or it has to be carried up stairs: at 23.1 kg it's far easier to move than the 38.8 kg Ultra X.
• An Ultra plus an AC Pro if you want the Ultra X's capacity split over two boxes. The AC Pro is a £699 1.92 kWh battery with no solar input that joins by a parallel cable, and two linked units can supply 2,300 W together.

Can you plug it into a socket in the UK?

No. Since 27 August 2026, SI 2026 No. 848 lets a verified solar kit be plugged into a socket, but its definition excludes a device “designed to import electrical energy from a low voltage consumer's installation for the purpose of storing energy for later supply”. The Ultra X charges from the grid at 1,200 W and the Ultra at 1,050 W, so on our reading both are outside it, as every battery is.

EcoFlow's UK FAQ agrees: “In the UK, local regulations require the EcoFlow STREAM DIY Cable to be wired into the distribution board, which must be done by a certified installer or electrician.” The Ultra and AC Pro pages go further and say the unit is supplied with a stripped-end cable and “must be installed by a certified, registered electrician”. The Ultra X page also carries a bullet saying set-up “requires no electrician”, next to a line that plug-in rules are “expected” in the coming months. Both are out of date. Go by the FAQ.

If you want solar you can plug in yourself, EcoFlow's battery-free STREAM plug-in kits are a different product and were verified on 22 September. They're among the 84 kits on our certification tracker.

Backup in a power cut

Both units keep their own sockets live when the grid goes down, up to 1,200 W. EcoFlow's manuals are careful about it: switching to battery power “may take up to 3 seconds”, and the unit is “not designed to function as an uninterruptible power supply”. One paid EcoFlow promotion on YouTube describes a 10 ms switchover; go by the manual. Only what's plugged into the unit keeps running, not the house.

Expanding it

EcoFlow allows up to six STREAM devices in one system, which is 23 kWh of Ultra X or 11.52 kWh of Ultra. In practice the add-on is the STREAM AC Pro at £699, joined with a £20 parallel cable. The Ultra X page mentions “STREAM Extra Batteries”, but no product by that name was on EcoFlow's UK store when we looked. EcoFlow sells the Ultra X with one or two AC Pros as a bundle, for 5.76 or 7.68 kWh in total.

The app, smart meters and subscriptions

A smart meter tells the battery what the house is drawing, so it can discharge to match. EcoFlow's manual lists its own Smart Meter, the EcoFlow × Shelly meter, Shelly 3EM and Pro 3EM, and the Tibber Pulse, and tariff links for Octopus and Tibber among others. EcoFlow's UK page says its AI time-of-use feature “requires a subscription”, and full control needs Wi-Fi and the app; Bluetooth alone gives limited local control. EcoFlow doesn't mention Home Assistant, though owners do report feeding the data into it.

What UK owners have measured

We haven't tested either unit, so these are the UK owners with actual numbers. Watch who supplied the kit: review units and paid promotions are common with EcoFlow.

A year on a STREAM Ultra: £335.13

Jonathan Tracey ran a STREAM Ultra and an AC Pro for a year on four panels hung vertically on a fence. After 365 days the system had saved £335.13, which he says is 16% of what it would have cost him, about £2,100, putting break-even at about five years. Part of that saving came from charging on a cheap overnight tariff in winter rather than from the sun, while vertical panels are close to the worst angle you can choose, so the two effects pull in opposite directions. EcoFlow supplied the units and, he says, had no editorial control.

An Ultra X bought with his own money

Tony, of Tony and Teddy's World, bought an Ultra X himself and paired it with a STREAM Max, about 5.8 kWh between them. In 28 days of April his panels brought in 138.87 kWh. It's a two-unit system, so read it as what a well-sited setup can do in spring, not a single-unit figure.

Two limits other owners found

UpsideDownFork, who links to EcoFlow with an affiliate code, found the Ultra X capped solar input at about 850 W while running off-grid, rising to 1,300 W once reconnected. Andrew Till, in a video marked as a paid promotion with EcoFlow, measured about 1.2 kW from the sockets off-grid and charged his car from it at about 1.15 kW. Neither is independent in the way Tony's is, but both measured what they report.

EcoFlow's savings claims

EcoFlow's UK pages quote savings of up to £1,729 a year for the Ultra X and £963 for the Ultra. The footnotes base them on German electricity prices and, for the Ultra X, a system of six units with 5 kW of panels. Tracey's £335 on one Ultra and an AC Pro is the better guide. Our savings calculator models the solar half for your postcode.

Where to buy

EcoFlow sells both direct and through its own Amazon UK listings, sold by EcoFlow Germany GmbH. The board at the top carries EcoFlow's prices with the date they were read; open the Amazon listing for its number, because the two don't always match.

Weighing a bigger battery? The STREAM 5000 vs Solarbank 4 Pro comparison covers the 5 kWh class.

Frequently asked questions