SolaX X1-IES hybrid inverter: specifications and warranty

The SolaX X1-IES is a single-phase, all-in-one home energy storage system: inverter, battery and controls in one enclosure, sold in power ratings from 2.5 kW to 8 kW¹. It is the single-phase member of SolaX's IES family, alongside the three-phase X3-IES, and it is aimed at homes that want solar, battery and backup in one box rather than a wall of separate units³.

The headline numbers are these. Continuous power runs from 2.5 kW to 8 kW, battery storage from 5.1 kWh with one module to 10.2 kWh with two, round-trip efficiency up to 98%, and a grid-failure changeover under 10 ms¹. The battery is LFP chemistry rated at more than 6,000 cycles, and the unit carries a 10 year battery warranty¹.

What that buys a household is a system that can run the house from its own roof and its own battery for much of the day, and keep selected circuits alive when the grid drops. What it does not buy is independence from the grid, from a supplier, or from SolaX's cloud service for the smart features. Those limits are set out below alongside the specifications.

What the X1-IES is: a single-phase, all-in-one storage system

SolaX describes the X1-IES as an all-in-one residential ESS, meaning the inverter, the battery and the energy management sit in one coordinated unit rather than as separate boxes on a garage wall¹. The design is described as all-in-one, plug-and-play, with multi-mode operation². The X1-IES-A is the variant of the same platform, and SolaX groups both under single-phase residential use³.

The distinction that matters most for a UK house is phase. Most homes are wired single-phase, and the X1-IES is built for that. SolaX's three-phase products, the X3-IES and X3-IES-A, are for properties with a three-phase supply, and the X3-IES-P is described as a three-phase hybrid storage system built specifically for residential applications⁶. A householder with a standard single-phase supply cannot use the three-phase units without a supply upgrade, so the X1-IES is the relevant family.

The all-in-one format has a practical consequence beyond tidiness. Because the battery and inverter are matched and shipped together, the system is sized as a package rather than assembled from parts, which simplifies the design stage. It also means the battery is not a separate purchase from a different maker, so there is one warranty relationship rather than two. For a household weighing hybrid inverters against a separate battery and inverter, the trade is flexibility for simplicity.

Power and battery range: 2.5 to 8 kW, and 5.1 to 10.2 kWh

The X1-IES spans 2.5 kW to 8 kW of continuous power, with models listed from the X1-IES-2.5K through to the X1-IES-8K⁴. That range covers a one-bedroom flat at the bottom and a large family house with a heat pump or an electric vehicle at the top. SolaX's own sizing guidance for inverters is that the unit should be matched to the array and the household load rather than bought at the largest size available, since an oversized inverter spends its life at low output where it is least efficient⁸.

Storage scales in modules. The datasheet lists one, two, three or four batteries, with a single module giving 5.1 kWh of rated energy and two giving 10.2 kWh¹. SolaX describes the X1-IES battery modules as spanning 5 to 20 kWh⁵. That is a large amount of storage for a domestic property, and enough to carry a well-insulated house through a winter evening and overnight.

The charge and discharge current is 50 A⁴. That figure governs how fast the battery can be filled from solar or cheap-rate electricity, and how much instantaneous load it can serve. A high current rating means a large battery is not throttled by a slow inverter, and short high-demand appliances can be run from the battery rather than imported. For a household on a time-of-use tariff, that combination is what makes overnight charging and evening discharge worthwhile.

Efficiency, chemistry and cycle life

SolaX states up to 98% round-trip efficiency for the X1-IES⁴. Round-trip efficiency is the proportion of energy that survives a full cycle in and out of the battery, so a 98% figure means roughly two units lost for every hundred stored. For comparison, SolaX quotes 98.5% for the three-phase X3-IES and up to 97% for the X1-Hybrid G4⁹. The differences between these figures are small and reflect different test conditions as much as different hardware.

The battery chemistry is LFP, written LiFePO4, and SolaX describes the X1-IES-A battery as cobalt free LiFePO4⁴. LFP is the chemistry most home storage makers have settled on because it is thermally stable and degrades slowly. The datasheet rates the battery at more than 6,000 cycles¹.

Cycle life is not the same as calendar life, and neither is a promise about a particular installation. A battery cycled once a day at 6,000 cycles is a very different proposition from one cycled twice a day, and depth of discharge affects how much capacity is available in practice¹¹. What the figure does tell a household is the order of magnitude: this is a battery designed to last the life of a typical solar installation rather than to be replaced midway.

Solar input and EPS output: 200% oversizing, two MPPTs

The X1-IES accepts up to 200% PV input power, meaning an array twice the inverter's rated capacity can be connected⁴. Oversizing is standard practice in the UK because a panel rarely produces its rated output: a west-facing array in Manchester and a south-facing array in Cornwall behave very differently, and the inverter's rating is a ceiling on output, not on connected panels. SolaX lists 200% oversizing and 200% PV input power on the datasheet¹.

There are two MPPTs across the model range, with an MPPT voltage range of 40 to 560 V⁴. Two trackers matter on a UK roof because they let two roof faces, or two strings with different shading, operate independently. A single-tracker inverter averages the two, so shade on one string drags down the other. The 40 to 560 V window is wide enough to accommodate a short string on a small roof and a longer string on a larger one without falling below the start-up voltage.

On the output side, the X1-IES supports up to 200% EPS output for 10 seconds on some operating conditions⁴. EPS is the emergency power supply mode: the circuit the inverter keeps live when the grid is down. A 200% surge for 10 seconds is what lets a fridge compressor, a pump or a small motor start, since these draw several times their running current at the moment of switch-on. The same 200% for 10 seconds figure appears across SolaX's storage range, including the X1-VAST and X3-IES-A¹².

For a household, the combination of 200% oversizing and 200% peak output means the system can be specified around real winter generation and real motor loads rather than around nameplate figures. The limits are the inverter's continuous rating and the size of the EPS circuit, not the array.

Backup and changeover: under 10 ms

SolaX states a UPS-level switchover under 10 ms on the X1-IES family, and the datasheet lists a switchover time of under 10 ms for EPS off-grid output with a battery connected⁴. The X1-IES-A is listed at under 10 ms⁴.

Ten milliseconds is roughly half a cycle of mains electricity. In practice that means lights stay on, a router stays up and a laptop does not reboot. It does not mean every appliance rides through. Motors and compressors may stall and restart, and anything with a sensitive power supply can still trip. The honest description is that the transfer is fast enough to be unnoticed by most equipment, not that the house never notices.

The wider SolaX range shows how much this figure varies by model. The X3-NEO-LV is listed at under 3 ms for a single unit, and the X1-LITE LV at under 6 ms¹⁴. Those are faster, but they are different products for different installations. For the X1-IES, under 10 ms is the figure to work from, and it is competitive with the hybrid inverters SolaX sells alongside it¹⁶.

What this means for independence is specific. The X1-IES keeps a chosen set of circuits alive during a power cut, drawing on the battery and, if the sun is out, on the array. It does not make the house independent of the grid, because the inverter is grid-tied and synchronised to the mains for normal operation, and it does not remove the need for a supplier for the energy the battery cannot cover. It reduces the consequences of an outage rather than removing the connection.

Cold weather and outdoor siting

The X1-IES is rated for an operating temperature range of -35 to 60 degrees C, with derating above 45 degrees C, and it uses natural cooling rather than a fan¹. Natural cooling means no moving part to fail and no fan noise, which matters for a unit mounted near a bedroom window. The trade is that heat has to escape by convection, so siting with clearance matters more than it would on a fan-cooled unit.

SolaX describes the X1-IES-A as having integrated battery heating technology for operation down to -30 degrees C³. Battery heating is the feature that makes cold-weather siting credible: LFP cells lose usable capacity and accept charge more slowly when they are cold, and a heater brings them into a workable band before charging begins. Without it, a battery in an unheated garage or on an external wall would underperform through a UK winter.

The datasheet lists natural cooling for the X1-IES, and the X1-Hybrid G4 datasheet lists both natural cooling and smart air cooling across its variants¹. Protection ratings vary across the SolaX range: the X1-Hybrid G4 is IP65, the X3-IES-P is IP66, and the X1-Micro Series is IP67¹⁶. The X1-IES datasheet does not state an IP rating in the material available, so outdoor siting should be confirmed with the installer against the installation manual rather than assumed from the family.

Smart features and monitoring

The X1-IES supports load management and time-of-use optimisation, and SolaX describes the all-in-one systems as emphasising smart energy management through SolaXCloud with forecast-led strategy control⁶. SolaXCloud provides real-time monitoring, load management and time-of-use optimisation, and SolaX's smart energy management material highlights real-time monitoring, tariff optimisation and automated energy control³.

The X1-IES-A adds Smart Schedule, intelligent loads management and Smart Scene¹⁹. In practice these are the features that let a household charge the battery when electricity is cheap and discharge it when it is expensive, and that decide whether surplus solar goes to the battery, to a hot water diverter or to an EV charger. SolaX lists smart load management for devices such as heat pumps and EV chargers on its hybrid range¹⁶.

This is where the dependence sits. Monitoring, tariff optimisation and remote control run through SolaXCloud, which means a home broadband connection, SolaX's servers and the SolaX app. A household that wants the battery to charge on a cheap overnight rate and discharge at peak is relying on that chain working. Local operation continues without it, but the automated optimisation does not. For a household whose reason for buying storage is independence, that is a real qualification: the system reduces dependence on the grid and the supplier, and adds a dependence on a cloud service and a manufacturer's software.

Cost in the UK

SolaX does not publish a UK list price for the X1-IES, and prices are installer-quoted. The figures that exist in the market are bundle prices for comparable all-in-one storage systems, which give a sense of the order of magnitude rather than a quote for this unit. One distributor's bundle pricing for a competing all-in-one system runs from £1,798 for a unit with a hub, through £2,198 and £2,398 for single-battery bundles, to £3,898 and £4,097 for larger configurations²⁰.

For context on the smaller end of home energy storage, independent guidance on plug-in solar suggests costs could start around £400 for a basic set up²². That is a different product category entirely, with no backup capability and a fraction of the storage, but it sets the floor against which larger systems are judged.

Three things move the price of an X1-IES installation: the power rating chosen, the number of battery modules, and the electrical work needed for the EPS circuits. A like-for-like replacement of an existing inverter is less work than a new installation with a dedicated backup circuit. VAT treatment is not stated in the figures above, so they should be read as quoted rather than as confirmed VAT-inclusive prices.

Availability is a separate question from price. SolaX battery systems reach UK households through UK installers²³. Stock timing varies by model and distributor: one trade listing showed the X1-IES 6.0K due in around 23 September 2026²⁴. Lead times are set at the point of order, and a household should confirm availability rather than assume it.

Warranty and registration

The X1-IES battery carries a 10 year warranty term¹. SolaX's warranty terms and conditions, version 1.7, took effect for products sold or installed on or after 10 September 2026, so the version in force at the point of sale is the one that governs a given unit¹⁹.

Warranty terms vary widely across the SolaX range, which is worth knowing when comparing models. The X1-Boost G4 carries 5 years¹⁸. The 10 year term on the X1-IES battery sits above that. Registration and claims run through SolaX's own process, and the paperwork that matters is the commissioning record and the serial numbers, which the installer should provide at handover.

For a household, the warranty is part of the independence picture rather than a footnote. A 10 year battery term covers the period over which the system is expected to pay back its cost, and it is a manufacturer's commitment rather than an installer's. It does not cover the installation work itself, which is a separate contract with the installer, and it does not cover the inverter's interaction with the rest of the system. Reading the terms alongside the solar panel warranties and degradation position gives a fuller picture of what is and is not covered over the life of an installation.