Compare
ProbeHarbor vs Shelly H&T Gen3 for freeze alerts
The Shelly H&T Gen3 costs $40.99, runs about a year on four AA batteries or from USB‑C, shows temperature and humidity on an e-paper display, and speaks Wi‑Fi, MQTT, and webhooks. It is a good sensor for a heated room. Shelly lists its ambient working temperature as 0°C to 40°C (32°F to 105°F) and 30–70% humidity, so an unheated garage or crawlspace in a cold snap is outside what it is rated for. ProbeHarbor is built for those spaces: a waterproof DS18B20 probe rated to −67°F on the pipe, with freeze, leak, and outage alerts and forecast warnings. If you already run Shelly gear indoors, its readings can reach ProbeHarbor through Home Assistant or MQTT.
ProbeHarbor vs Shelly H&T
| Capability | ProbeHarbor | Shelly H&T |
|---|---|---|
| Hardware | DIY: ESP32 / Pico / Arduino + DS18B20 or DHT22 | Finished Wi‑Fi sensor with e-paper display |
| Up-front cost | About $25 in parts per probe | $40.99 |
| Rated working temperature | DS18B20 probe: −67°F to 257°F | 32°F to 105°F (0°C to 40°C) |
| Pipe-mounted probe | Yes (waterproof DS18B20 on the pipe) | No; measures air at the device |
| Power | USB power at the board | 4 AA batteries (about 1 year) or USB‑C |
| Local integrations | Home Assistant (HACS), ESPHome, MQTT bridge | MQTT and webhooks (URL actions) |
| Leak / flood contacts | Yes, alert automatically when wet | Not on this device |
When to choose which
Choose ProbeHarbor when
- The space can drop below 32°F, which is outside the Shelly H&T's rated range
- You want the reading at the pipe, under the insulation, not the air in the room
- You want freeze, leak, and sensor-offline alerts and a forecast warning without building automations
- You want household members to receive alerts through household invites
Choose Shelly H&T when
- You are monitoring a heated room: a basement, utility room, or living space
- You want a battery sensor with a display and no wiring
- You already use the Shelly app, Home Assistant, or MQTT and will build the alert yourself
- Humidity in a conditioned space matters more than pipe temperature
Frequently asked questions
Straight answers for people comparing ProbeHarbor to Shelly H&T.
Can a Shelly H&T be used in an unheated garage?
Shelly lists the H&T Gen3's ambient working temperature as 0°C to 40°C (32°F to 105°F). A garage that drops below freezing is outside that range, so it is the wrong tool for a freeze alarm there.
Can a Shelly device send readings to ProbeHarbor?
Yes. The simplest route for an H&T is through Home Assistant or MQTT, which ProbeHarbor has an integration and a bridge recipe for. The ESPHome and Shelly recipes guide at probeharbor.dev/about/esphome-shelly-recipes covers posting directly from Shelly Plus and Gen2 modules.
Is a Shelly H&T cheaper than a ProbeHarbor probe?
No. The H&T Gen3 is $40.99; an ESP32 with a waterproof DS18B20 is about $25 in parts. The Shelly is finished and battery powered, which is what the extra money buys.
Sources
Shelly H&T details come from their own pages, checked October 2026. Prices change; check before you buy.
Related answers
Next steps
Start free with live charts, email alerts, and a family live share link, or compare plans when you need SMS, CSV history, and expanded Pro share scopes.