Claude to build a home-energy controller

Simon Monk used Claude Code across more than ninety development sessions to build a controller for his Sydney home's solar panels, Powerwall battery and electric vehicle. The system began on a Mac Studio and moved to a Raspberry Pi connected to Home Assistant.

A crucial design change came from observed failures. The early language-model controller had about ten rules but invented prices and made inconsistent decisions. Monk moved the actual control into deterministic Python rules, running every thirty minutes. Claude Code remained the tool used to build and debug the system; it should not be confused with an LLM autonomously choosing the current charging actions.

The project also gained a forecast that calibrated hourly bias using previous observations. A more sophisticated optimization model ran in shadow mode, allowing comparison without handing it control. That comparison later proved unreliable: two Home Assistant configuration instances had diverged, leaving the shadow model without battery state-of-charge data for seven weeks.

Monk reports that monthly demand charges fell from $88 to $6, but that is his account of this installation, not independently verified savings or a result transferable to every tariff. The useful lesson is operational: check decisions against observed data, keep experimental control in shadow mode, and investigate configuration consistency before trusting a comparison.

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Source: www.linkedin.com · Simon Monk