Built my own solar water heater monitor — e-paper display, LoRa, no WiFi, and no more cold showers

[u/Creative-Trip-8032]

Hey folks —
I live in a home with a solar water heater, and I got tired of guessing whether the tank was hot enough for a shower or if I needed to switch on backup heating.

So I built a system that monitors my solar tank temperature + outdoor weather conditions, shows it on an e-paper display indoors, and runs fully on LoRa — no WiFi, no wiring to the roof, no cloud dependency unless you want it.

Here’s what it does:

• Measures tank temperature with a PT100 industrial sensor
• Tracks weather via SHT30
• Transmits data wirelessly (LoRa, range is solid even through walls)
• Indoor unit shows tank temp + weather on an always-on e-paper display
• Optional cloud dashboard via Grafana (for alerts and history)
• Battery life: Over a year per unit

I’m testing it now, and planning to launch it soon via Kickstarter. I’d love to hear what other smart home folks think — especially:

• Would you want this to integrate with something like Home Assistant?
• Should I prioritize the cloud dashboard or local-only features?

Images:

• Display showing hot water temp
• Sensor attached to tank
• Grafana dashboard

Appreciate any feedback or wishlist ideas — especially from other solar/home energy nerds here!

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(If you're curious, I made a short video demo here: https://www.youtube.com/watch?v=TqCx3jfl0tQ )
Early signup page for launch: https://omnisense.gr