An AC+ that is neither the AC nor the Pro: three devices not to be confused
The name invites confusion, and confusion is expensive at the till. The SolarFlow 2400 AC+ (model ZDSF2400AC+, introduced in February 2026) is a single block: a 2400 W bidirectional inverter and a 2400 Wh LiFePO4 battery (50 Ah at 48 V) in a 326 x 294 x 251 mm case weighing 27.8 kg. It has no input for solar panels: it only stores alternating current, either the surplus from solar panels that are already installed or mains electricity when it is cheap.
The SolarFlow 2400 AC that came before it is a different product: an inverter sold without storage, paired with AB3000X modules that do not fit under the AC+. The SolarFlow 2400 Pro shares the AC+ case and electronics but adds four MPPT solar inputs. The figures in this review apply to the AC+ only.
| Criterion | 2400 AC+ (this product) | 2400 AC | 2400 Pro |
|---|---|---|---|
| Base battery | 2400 Wh built in | None, AB3000X modules sold separately | 2400 Wh built in |
| Direct solar input | None (AC coupling) | None (AC coupling) | 4 MPPT, 3000 W |
| Expansion modules | AB3000L (AB1000 and AB2000 per the manual) | AB3000X | AB3000L |
| Maximum capacity | 16.8 kWh (5 modules) | 17.28 kWh (6 modules) | 16.8 kWh (5 modules) |
Efficiency: about 88% at 800 W, well short of the claimed 93%
Zendure claims up to 93% round-trip efficiency on the AC side, thanks to silicon carbide semiconductors. Over full cycles from 10 to 100% with 800 W on both charge and discharge, the figure comes out at 87.3, 88.2, 88.7 and then 88.4%, or about 88%. The five-point gap with the spec sheet amounts to roughly fifty watt-hours lost for every kWh stored.
That figure does not tell the whole story, because the inverter draws an almost fixed amount of power: the lower the load, the more that draw weighs. In zero-export regulation, when the battery delivers only 100 to 200 W, efficiency drops to between 78 and 82%. That is a common regime overnight, and therefore the one that counts for real savings. The unit works best when it is made to work hard, for instance by emptying it over a few hours at peak tariffs or by taking advantage of negative prices.
On standby the unit draws about 3 W when it runs on its own battery, and under 1 W when the grid supplies it: at 3 W continuously, that amounts to around 25 kWh a year. Switching it fully off removes the draw, and enabling the backup socket increases it. As a point of reference, the earlier SolarFlow 2400 AC, with a separate inverter, sits a little lower, between 86 and 87%.
2400 W on the spec sheet, 800 W at the socket
The 2400 W that features in the marketing is not available out of the box. The unit ships with grid export limited to 800 W, and the manual lists ceilings by country to stay within the rules for plug-in kits: 800 W in Germany, Belgium, the Netherlands and Austria, 900 W in France, 600 W in Switzerland and 350 W in Italy. The UK is not on that list. Going above the ceiling requires a dedicated circuit checked by an electrician, followed by a signed declaration in the app confirming that the check took place. The manufacturer accepts liability only for the quality and safety of the unit, not for the installation.
Three other figures frame these values: the battery accepts 2400 W on both charge and discharge, the AC input handles up to 3200 W, and the backup socket delivers 3200 W as long as the grid is present, with 2400 W coming from the battery and the rest from the mains. That last step has nothing to do with export: it exists to power a demanding appliance directly from the unit.
The 800 W ceiling changes how the spec sheet should be read: in the evening, an oven, a hob and a washing machine together far exceed that threshold, and the shortfall is then drawn from the grid. The full 2400 W is for those prepared to have a dedicated circuit fitted, with an electrician's bill on top of the price of the unit.
Control: a smart meter is essential, ZENKI still uneven
Without a smart meter, the AC+ follows a fixed charge and discharge plan, 200 W by default. To match discharge to the household's consumption, it needs a compatible meter: the maker's Smart Meter 3CT-S or 1CT-S (connected to the RJ45 port, which is an RS485 port and not a network socket), a Shelly Pro 3EM or an EverHome EcoTracker. In the UK a Smart Meter 1CT-S is included in the current launch offer.
| Mode | How it works | Requirements |
|---|---|---|
| Auto | Priority to the meter, then to the smart plug, then to the base plan; follows prices if a dynamic tariff is entered | Meter recommended |
| ZENKI | Weather forecasts, consumption history and electricity prices (more than 840 European suppliers) | Internet connection, meter, about a week of learning |
| Expert | Four sub-modes: meter, smart plug, base load (10 time slots), electricity price with thresholds | Manual settings |
ZENKI's decisions are sometimes hard to justify: charging from the grid when the next day's solar surplus has been forecast, discharging at a tariff that is not particularly high, or charging overnight at off-peak rates so that there is no room left for the morning sun. Auto mode, which is more predictable, is the safest choice for anyone without a dynamic tariff. ZENKI covers 25 UK energy suppliers for its tariff data.
Regulation is fast, within a few seconds, but it deliberately keeps a margin of about 50 W around zero to spare the relay. A small residual export therefore remains, most visible in winter. Over a six-hour night, cumulative import stays at around 20 to 40 Wh with a Shelly meter or the maker's D0 reader, for an export below 15 Wh. This margin belongs to the manufacturer's own energy manager: it can be avoided by controlling the unit through the local API or MQTT, with Home Assistant for example.
That leaves cloud dependence: the app goes through the manufacturer's servers, ZENKI needs a connection to retrieve prices and weather, and the unit accepts only 2.4 GHz Wi-Fi. Without a connection it falls back on less refined local rules. A local API (HTTP) and an official Home Assistant integration that can be pointed at a local MQTT broker allow a way round this for those who can configure them. The manufacturer publishes no subscription price for HEMS or ZENKI, and promised in 2025 that its functions would remain free for the warranty period of each unit, which is ten years for the AC+.
From 2.4 to 16.8 kWh: what expansion costs
The 2.4 kWh base capacity is tight for a full evening: it covers a frugal household, not a family that cooks on electricity. Expansion is by 2.88 kWh AB3000L modules that stack under the unit, are recognised automatically and go up to five, or 16.8 kWh in total. Power stays at 2400 W whatever the number of modules: 16.8 kWh empties in about seven hours at full power, against under an hour for the unit alone.
On compatibility, the manufacturer also declares the AB1000 and AB2000 modules compatible but recommends only the AB3000L: the other models do not fit the unit's dimensions, and after-sales support may be limited for a non-recommended configuration. The AB3000X from the earlier 2400 AC does not fit.
On 9 October 2026 the 2.4 kWh unit is listed at £899 with the manufacturer, in stock and with a Smart Meter 1CT-S included under a launch offer that runs to 15 October, and each module costs £699. The cost per kWh of the full configuration falls to £262, an attractive level for AC-coupled storage, but the starting capacity remains the most expensive per kWh (£375).
| Configuration | Capacity | Price | Price per kWh |
|---|---|---|---|
| Unit alone | 2.4 kWh | £899 | £375 |
| Unit + 1 module | 5.28 kWh | £1,598 | £303 |
| Unit + 2 modules | 8.16 kWh | £2,297 | £281 |
| Unit + 3 modules | 11.04 kWh | £2,996 | £271 |
| Unit + 4 modules | 13.92 kWh | £3,695 | £265 |
| Unit + 5 modules | 16.8 kWh | £4,394 | £262 |
The backup socket: powerful, but not an uninterruptible supply
The Schuko-type socket on the side is disabled by default and is switched on from the app. It delivers 2400 W continuously and up to 3600 W for 200 ms when an appliance starts; with the grid present, it rises to 3200 W, the top-up coming from the mains. It also accepts, as an input, a micro-inverter of 2400 W at most to charge the battery, but only while the unit is connected to the grid. A petrol or diesel generator must never be connected to it. When the grid disappears, it switches over to the battery.
There are three limits to know about. First, no switchover time is guaranteed: the manual gives none, and the manufacturer does not present the unit as an uninterruptible power supply (UPS). A desktop computer or a server needs its own protection. Second, only the appliances plugged into this socket are backed up, not the rest of the home. Finally, runtime melts away: at 2400 W, the unit's 2.4 kWh last under an hour.
Normal mode keeps the socket live permanently and nibbles at the battery; Eco mode puts it to sleep after two hours without a load. Enabling the socket raises the standby draw, and the battery may then drop below the reserve that has been set. A fridge, a router, lighting and a laptop are fine; an induction hob or a water heater empties the battery very quickly.
Installation and compliance: what changes in the UK
The UK listing presents the AC+ differently from the plug-in devices sold in Germany or France. The unit is certified under ENA G98, and the manufacturer's own UK guidance is to hardwire it to the consumer unit using the hardwiring terminals supplied, with the work carried out by a Part P-qualified electrician. That puts it closer to a fitted home battery than to a device simply plugged into a socket. The manual's country table does not list the UK, and its default export limit of 800 W applies until it is changed in the app after an electrician's check.
Physical installation is quick once the wiring is done: the unit weighs 27.8 kg and has two handles on the sides; it can go indoors or outdoors (IP65), out of direct sun and rain, with at least 15 cm between the aerial and the wall and the clearances in the manual around the rear fins. The meter, whose clamps go into the consumer unit, takes half an hour to an hour. The manual states that the system is grid-tied and that it is up to the user to check what is allowed locally.
For stacking, the manual recommends fixing the unit and its modules together with the brackets and screws supplied. In May 2026 the manufacturer published a safety notice about the earlier 2400 AC, whose terminals can overheat when the stack is not sitting flat; the AC+ is not named, but checking that the stack is level and tightening the fixings applies here too.
Silence, heat, safety and warranty
The metal case with its fins doubles as a heatsink: there is no fan, so no noise apart from the click of the relay each time charging starts or stops. After two hours of charging at 800 W, the hottest point (the rear face) reaches 33 °C, with the other points staying between 25 and 31 °C. The IP65 rating applies to the case; the backup socket is not watertight in use or with its cover open.
ZenGuard combines three levels of protection: a dual BMS (local, with cell health monitoring in the cloud), a mechanical pressure-relief valve and an aerosol extinguishing module that triggers at around 170 °C. The battery heats itself in cold weather (discharge from -20 °C to 55 °C, charging from 0 °C) and discharge stops at 5% charge.
The warranty is ten years for the unit and for the AB3000L modules, with 6000 cycles claimed and a service life of up to fifteen years. The cell clause deserves a read: it lapses if the battery is not fully charged within 30 days of delivery and then recharged at least once every three months. A no-fault return remains possible within 30 days, but the return shipping costs of an appliance this heavy are charged to the buyer.
The track record is eight months, and the firmware still has teething troubles. The reserve set by the user is not always respected during the first cycles: the battery can end up at 2 or 5% when the reserve is 15 or 10%, so the first few days need watching. In one isolated case it stays stuck at 8%, with an update that needs 10% charge to install. Error 52 (“grid voltage too low”, shown while the voltage is normal) led in one isolated case to the manufacturer replacing the units. No recall of this model has been announced to date. The manufacturer has, however, had a fire on the AiO 2400 in 2025, from which it rules out the cells, and issued the May 2026 safety notice on the earlier 2400 AC: those two products are distinct from the AC+, but they weigh on confidence in the brand.
Against the other home batteries
Against the other home batteries, the AC+ stands out first for its AC power: 2400 W, against 1000 to 1200 W for the Hoymiles and the two MPPT models, with only the Marstek edging past it (2500 W). Its starting price is below those of the Anker and the EcoFlow, which regain the advantage as soon as panels have to be connected without a micro-inverter, thanks to their solar inputs.
| Criterion | Zendure SolarFlow 2400 AC+ | Hoymiles HiBattery 1920 AC | Marstek Venus E 3.0 | Anker Solix Solarbank 3 E2700 Pro | EcoFlow Stream Ultra X |
|---|---|---|---|---|---|
| Starting capacity | 2.4 kWh | 1.92 kWh | 5.12 kWh | 2.69 kWh | 3.84 kWh |
| Maximum capacity | 16.8 kWh | 11.52 kWh | Not expandable | 16.13 kWh | 23.04 kWh |
| Maximum AC power | 2400 W | 1000 W | 2500 W | 1200 W | 1200 W |
| Direct solar input | None | None | None | 4 MPPT, 3600 W | 4 MPPT, 2000 W |
| Weight | 27.8 kg | 24 kg | 60 kg | 29.2 kg | 39 kg |
| Catalogue price | £899 | £674 | £1,400 | £897 | £1,299 |
| Price per starting kWh | £375 | £351 | £273 | £334 | £338 |
The Hoymiles is the cheapest but the least powerful, and its expansion stops at 11.52 kWh. The Marstek offers the cheapest kWh, but its capacity is fixed and its 60 kg makes it hard to move. Against the only AC-coupled rival of comparable power, the Marstek, the AC+ gains in expandability and weighs half as much (27.8 kg against 60 kg), but offers half the capacity to start with.
Who the AC+ suits, and who it does not
The AC+ is aimed first at people who already have panels and an inverter or micro-inverters, want to store the surplus without touching the solar wiring and have a communicating meter within reach. It also suits a home without panels but with a dynamic tariff, since charging can come from the grid. A balcony-kit micro-inverter can even be plugged into its side socket.
It suits less well anyone who wants to connect panels directly (the SolarFlow 2400 Pro is designed for that), anyone expecting uninterrupted backup for sensitive equipment, or anyone who demands zero export to the watt without going through the local API. It also suits badly anyone hoping to use the full 2400 W without an electrician.
A practical buying tip: start with the unit alone and the meter, check how the first cycles behave (discharge reserve, app and firmware up to date), then add AB3000L modules once the need for capacity is confirmed. The modules from the earlier 2400 AC are of no use here.
