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The Challenge
The existing system used a standard string inverter from a different manufacturer, so a compatible battery solution was needed. The customer also wanted the battery to act as a backup during grid outages — a requirement that not all battery systems support.
Our Solution
We installed a Fox ESS All-in-One inverter/battery unit alongside the existing generation inverter, using AC coupling. This approach works with any solar system regardless of brand. The Fox ESS unit supports backup power mode, providing islanding capability during a power cut for essential circuits.
The Outcome
Self-consumption has increased from 38% to 84%, reducing grid imports by over 1,800 kWh per year. Annual electricity cost savings have increased by approximately £540, giving a payback period for the battery of around 6 years. The customer used the backup mode during a local grid fault in March 2026.
System Installed
Fox ESS All-in-One 9.5 kWh battery, AC coupling with existing SMA inverter, CT clamp, backup power relay
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