Your energy bill doubled last month. You have no idea why. The utility company shows you one number — a monthly total — and expects you to just pay it.
What if you tracked every spike yourself? On your own server. No app that sells your usage data to advertisers.
Here's how to build a private energy log in an afternoon.
1. Log readings instead of guessing
Most people check their meter once a month — when the bill arrives. That's too late.
Start with a simple habit: snap your meter reading every Sunday. Store the number, the date, and a note ("ran AC all weekend"). Four readings a month beats one. You'll see the trend climb before the bill confirms it.
A self-hosted spreadsheet or a tiny Grafana dashboard works. The point is: the data lives on your machine, not in a utility app that profiles your schedule.
2. Use a cheap smart plug — locally
Want to know what's really eating power? Put a smart plug on one suspect device — the old fridge, the space heater, the gaming rig.
Buy a plug that works with Home Assistant and flash it or pick one with local control. Many cloud plugs phone home every few seconds, reporting exactly when you're awake and active. A locally-controlled plug keeps that pattern inside your walls.
You'll find out that one 15-year-old fridge is quietly costing you more than everything else combined.
3. Build a one-screen dashboard
Numbers in a table are easy to ignore. A line that spikes is not.
Run Home Assistant or Grafana in a Docker container. Feed it your weekly readings and plug data. Set the chart to show cost, not just watts — multiply by your rate. Suddenly "0.4 kWh" becomes "that's 12 cents an hour, every hour, all night."
Seeing money, not units, changes behavior fast.
4. Set a threshold alert
The real win: catch the problem while you can still act.
Configure an alert when daily use crosses a line you set. Home Assistant can ping your phone, send an email, or flash a light. When your usage jumps 40% over your normal day, you'll know that day — not 29 days later when the bill lands.
This is the difference between "why is my bill so high?" and "the water heater element is failing, let me fix it now."
Why self-host this at all
Utility apps and smart-home clouds build a minute-by-minute map of your life: when you wake, when you leave, when you sleep. That map is worth money to data brokers.
Keep it local and the map stays yours.
Your one action today: write down your meter reading right now, with the date. Next Sunday, write it again. You've already started the log — the dashboard can come later.