What the product is and who it suits

Fox ESS T15-G3 is a 15kW three-phase string inverter in the T Series (G3) range. It is intended for grid-connected solar PV systems and sits in the middle of Fox's higher-output three-phase string line, giving buyers more headroom than 10kW or 12kW models without moving up to 20kW or 25kW hardware. Fox positions the range for three-phase domestic and small-scale commercial installations, which makes the T15-G3 a sensible choice for larger homes and small commercial premises where array size and site supply call for a true three-phase solution. On the LAMPS site it also sits naturally alongside the wider three-phase solar inverter range and the broader Fox ESS line-up.

The practical point of this variant is output. A 15kW AC rating gives more scope for larger rooftop or ground-mounted PV designs than lower-output models. At the same time, the T15-G3 remains compact enough for normal inverter locations, with a listed enclosure size of 370 × 480 × 183.5mm and a weight of 21kg. That combination matters for installers who want a step up in power without moving to a much bulkier commercial chassis.

Key features and practical benefits

Generation performance is built around a wide 140 to 1000V MPPT operating window, a 140V start-up voltage, two independent MPPTs and a maximum efficiency of 98.6%. Fox also lists 99.8% MPPT efficiency and 97.8% European efficiency. In practice, that means the inverter can start earlier in lower light, hold a wide range of string voltages, and manage more complex roof layouts without forcing the whole array onto a single tracking point. For sites with separate east and west roof faces, or different string lengths within sensible design limits, the dual-MPPT layout helps reduce mismatch and makes system design less restrictive.

The T15-G3 also allows up to 22,500W of maximum PV input power, with 28A maximum input current and 36.4A maximum short-circuit current. Fox lists 2+2 strings per MPPT on this 15kW model. That gives designers useful flexibility on larger arrays and helps the inverter suit installations where the DC side is intentionally oversized within manufacturer limits to stretch output across more of the day.

• 15,000W rated AC output with 16,500VA maximum output apparent power
• 22,500W maximum PV input power for larger three-phase array designs
• Two MPPTs with 2+2 strings per tracker on the T15-G3
• 140V start-up voltage and 140 to 1000V MPPT range
• 98.6% maximum efficiency, 97.8% European efficiency and 99.8% MPPT efficiency

Technical detail that matters in practice

Some inverter specifications look technical but have a direct buying impact. Rated output current on the T15-G3 is 21.7A, with a maximum output current of 23.9A. Total harmonic distortion is listed below 3%, and power factor is adjustable from 0.8 leading to 0.8 lagging. Those details matter on sites where grid behaviour, power quality and export behaviour form part of the approval or commissioning conversation, especially on larger properties and small commercial projects.

Fox also lists rated grid voltage options of 3/N/PE, 220/380, 230/400 and 240/415V at 50/60Hz. That underlines the fact that the T15-G3 is for genuine three-phase grid environments, not a workaround for oversized single-phase systems. A higher-output inverter is only useful where the incoming supply and the installation design allow it.

Noise and cooling matter too. The T15-G3 uses fan cooling rather than the natural convection approach seen on some smaller models in the same family. Fox lists typical noise below 55dB. For most plant rooms, service areas and protected outdoor walls that is still a manageable level, but it is worth knowing because it is different from smaller, quieter convection-cooled units. Operating temperature is listed from -25°C to 60°C, humidity from 0 to 100% with no condensation, and maximum operating altitude at 3000m. Those figures make it a credible outdoor unit for UK conditions when installed to the manual and with sensible siting.

Installation, monitoring and control

Housing protection is IP65, so the inverter is suitable for outdoor installation where the site layout demands it. A compact footprint and 21kg unit weight help with siting, while the manual makes clear that installation and maintenance should be carried out by qualified electricians. That is important on three-phase equipment, where cable sizing, protection, isolation and commissioning all need to line up with the site design and local rules.

Monitoring and communications are stronger than the basic spec line might suggest. Fox describes multiple communication options including WiFi, 4G, RS485 and meter connection. The inverter can be monitored locally or remotely through those interfaces, and FoxCloud V2.0 is the monitoring platform referenced in the datasheet. WiFi and 4G devices are optional, while the communication port also supports RS485-1 for inverter monitoring and RS485-2 for smart meter connection. For buyers who need more than a simple fit-and-forget inverter, that opens the door to ongoing performance visibility, remote fault awareness and easier aftercare.

The smart meter side is especially useful. Fox states that the T-G3 inverter has integrated export limitation functionality, and the manual says a power meter must be installed on the grid side to use it. The same section also refers to CT or meter feedback for hard and soft export limiting. That matters on constrained connections, sites with DNO export rules, and projects where self-consumption strategy is part of the brief. For related system components, buyers often pair an inverter like this with optimisers and meters, suitable solar panels, and proven solar mounting systems.

Protection, compliance and warranty

Fox gives the T15-G3 a well-developed protection set for this class of inverter. The datasheet lists insulation monitoring, residual current monitoring, DC reverse polarity protection, anti-islanding protection by frequency shift, AC short-circuit protection, AC overcurrent protection, AC overvoltage protection, DC/AC Type II surge protection, a DC switch, optional AFCI, and Class I protective class. PV string current monitoring is marked optional on the T15-G3. For installers and specifiers, the value here is not just a longer feature list. These are the functions that support safer installation, clearer fault handling and a neater route through commissioning on real sites.

Safety compliance is listed as IEC62109-1/2. Grid regulation lines shown in the datasheet include G98, G99 and EN50549-1, alongside other regional standards. That makes the inverter easier to specify for UK work where recognised grid and safety standards matter. As always, the final installation still needs to follow the current local approval and commissioning process.

Warranty is worth reading closely because Fox gives both a standard period and a route to longer cover. Under the current UK & Ireland Fox inverter warranty policy, the standard warranty is sixty months from the date of installation, capped at sixty-five months from the date of manufacture, whichever comes first. For T Series units, Fox also states that an additional sixty months can be provided beyond the standard term when the product is registered through the Fox website within the stated timeframe and successfully registered to the Fox Cloud platform using a Fox datalogger for remote monitoring. For buyers who want the best long-term cover, registration should not be left until much later in the project lifecycle.

Why this variant may be the right choice

The main reason to choose the T15-G3 over a smaller T Series model is straightforward. It gives 15kW rated AC output and 22.5kW maximum PV input capacity in a package that is still recognisably a mainstream three-phase string inverter rather than a jump into a more specialised commercial platform. That makes it a good middle-ground choice for sites that have already outgrown 10kW or 12kW equipment but do not need the 20kW or 25kW end of the range.

That matters for system matching. A designer working with a larger domestic roof or a small commercial array can choose the T15-G3 because it provides more headroom without automatically forcing a bigger step in budget, electrical design or installation space. If the project is closer to 10kW AC output, the Fox ESS T10-G3 is the nearer sibling. If the array size or site demand points higher, the Fox ESS T20-G3 moves the range up to 20kW. The T15-G3 is the model that fills the gap between those two decisions.

Battery plans are another area where care matters. The T Series datasheet states that the range is fully optimised for upgrade to the Fox range of battery storage system, with additional Fox equipment required. That gives buyers a path into storage planning inside the same ecosystem, but it is still important to treat the T15-G3 as a string inverter first and confirm the exact upgrade hardware before ordering a storage add-on. Buyers already looking at storage can review the wider solar batteries range alongside the inverter page.

Frequently asked questions

Loading delivery information...