Why I Track Every Watt: Building a Home Energy Dashboard
Six months ago I installed a Shelly EM on my main breaker panel. Since then I have collected over 4 million data points about my home energy consumption. Here is what I learned and how you can build the same monitoring system for under $80.
The Setup
The Shelly EM clips onto your breaker panel wires without cutting anything. It measures real-time wattage and reports to Home Assistant via WiFi. I paired it with a Grafana dashboard that shows consumption by hour, day, and month.
What the Data Revealed
My biggest surprise was phantom load. Devices on standby were consuming 340 watts continuously – that is $30 per month doing nothing. The second insight was my heat pump cycling pattern. It was running 12-minute cycles instead of longer, more efficient 20-minute ones because my thermostat deadband was too tight.
Changes I Made
Smart plugs on entertainment center and office equipment cut phantom load by 280 watts. Widening the thermostat deadband from 0.5F to 1.5F reduced compressor cycles by 35% and lowered my electricity bill by $47 per month. Total investment: $120 in smart plugs plus the $45 Shelly EM. Payback period: 23 days.
The point is simple. You cannot improve what you do not measure. A home energy dashboard is the foundation of any serious optimization effort.
