The Easun Power ISolar SMK series are off-grid inverters with UPS functionality, designed to power homes or businesses using PV and batteries - even in locations where the grid is unstable or unavailable. A key feature is zero transfer time, which effectively protects sensitive equipment (such as servers, monitoring systems, and automation) from power interruptions. The built-in MPPT charge controller ensures optimal energy harvest from solar panels, with benefits particularly noticeable under variable weather conditions. In practice, the SMK series uses a single MPPT, simplifying configuration for installations with uniformly oriented modules.
In terms of energy production efficiency, European efficiency is crucial - it demonstrates how the inverter performs under typical daily conditions, not just in an ideal test scenario. Monitoring is supported via Bluetooth and a mobile app, and communication with the system can be based on USB or RS232/RS485. Additionally, a BMS port is provided, facilitating integration with energy storage systems and battery operation monitoring. The series is primarily intended for residential and small commercial installations; it typically offers parallel operation and declared CE compliance, with warranty depending on the sales channel.
Ranking
Specifications
Pros and cons
A transfer time of 0 ms (true online UPS) effectively protects sensitive devices - servers, monitoring systems, and automation - from even the smallest power interruptions. Budget-friendly off-grid inverters (e.g., Voltronic Axpert) claim transfer times of 10-20 ms, which makes them unsuitable for protecting IT equipment.
The SMK series supports parallel connection to up to 9 inverters, enabling power expansion, for example, to 45 kW (9 × 5 kW). This is a rare feature in the budget-friendly off-grid inverter segment, providing scalability for small commercial installations.
The integrated BMS port (RS485/CAN-BUS/RS232) enables direct communication with LiFePO₄ energy storage systems without the need for additional converters. Monitoring via Bluetooth and a mobile app is available without the need to purchase separate Wi-Fi modules, which reduces the overall installation cost.
The declared THD (Total Harmonic Distortion) below 3% for linear loads and below 8% for non-linear loads complies with the EN 62040-3 standard for VFI-SS-111 class inverters, as confirmed by the technical data published in the ENF Solar Datasheet.
The 5K model provides a peak power of 10,000 VA for 5 seconds, allowing for the start-up of electric motors (pumps, compressors) without overloading. A 2:1 (surge:nominal) ratio is the industry standard, but is particularly important for installations with inductive loads.
ISolar SMK is marked as discontinued. This means limited availability of spare parts, lack of firmware updates, and the risk of no longer receiving service support after the warranty period expires. For new installations, actively developed series (such as ISolar SMH III or newer) are recommended.
The SMK series only has one MPPT input channel, which prevents connecting strings of panels with different orientations or tilt angles without performance losses. Competitive models in a comparable price range, such as the Deye SUN-5K-SG03LP1, offer 2 independent MPPT channels.
The inverter's efficiency in battery mode is declared at 90%, while more advanced premium-class units (such as Victron MultiPlus-II 5000 and SMA Sunny Island) achieve 95-96%. The difference of 5-6 percentage points translates into measurable losses during intensive off-grid operation.
Alternatives
About the ISolar SMK series
These answers cover the whole series. Where a figure differs, the specification above is this model's own.