2026 verdict
Behind a wall switch the two look identical, and the
Shelly 1PM Gen4 is the better smart relay because it adds power metering and full electrical protection.
It measures power, voltage and total consumption, and it guards against overvoltage, overcurrent and overpower as well as overheating, where the
Shelly 1 Gen4 only protects against heat. Everything else is shared: the same 37 x 42 x 16 mm body, a 16A rating, dry and wet contacts, AC or low-voltage DC supply, Wi-Fi, Bluetooth, Zigbee and Matter in one module, Zigbee routing, a three-year warranty and support for Alexa, Google Home, Apple Home, SmartThings and Home Assistant. The
Shelly 1 Gen4 is the cheaper of the two. Pick the
Shelly 1 Gen4 for garage doors, pumps and lights where only switching matters, and the
Shelly 1PM Gen4 for heaters, boilers or anything whose consumption you want to see.
What owners say
Owners of both Gen4 relays praise the same foundation: local control with no cloud, easy Home Assistant integration and the freedom to pick Wi-Fi, Zigbee or Matter. Shelly 1 Gen4 owners lean on the dry contacts for momentary garage door triggers, pool heater relays and low-voltage lights, and on detached mode to turn a dumb switch into a scene controller; they warn that Zigbee pairing can be painful, notably on Hubitat, and that it is a tight fit in a crowded box. Shelly 1PM Gen4 owners talk about the metering, watching how often a water heater runs, keeping a wall tablet charged between set levels and monitoring a boiler, and they complain about an unconventional wiring diagram, tiny printed instructions and firm button presses needed to switch radios.
