Shelly 1 Gen3 vs Shelly 2PM Gen4

The Shelly 2PM Gen4 is better overall thanks to its two channels, per-channel energy monitoring, full overheating/overvoltage/overcurrent/overpower protection, added Zigbee and cover mode, plus a higher owner rating. The Shelly 1 Gen3 is the pick when you only need one channel, want DC power or want to spend less.

Channel count and scope. The 2PM Gen4 controls two circuits, adds per-channel metering, a roller-shutter cover mode and a full protection suite. The Gen3 is a single-channel relay with no metering. Both need a neutral wire on mains power.

Yes. The 2PM Gen4 has an interlock/cover mode with obstacle detection built for roller shutters, blinds and gates, driving a motor up and down from one module. The Shelly 1 Gen3 is a single-channel relay without cover mode, so it is not suited to that job.

On mains power, yes, both do, so neither suits a switch box that lacks one. The Shelly 1 Gen3 can instead be powered from a 12V or 24-48V DC supply, where no neutral is needed; the Shelly 2PM Gen4 does not document a DC supply.

Buy the Shelly 1 Gen3 if you need one channel, want to power it from low-voltage DC, or want the cheaper module. Its dry and wet contacts make it a flexible fit for garage doors, pumps and irrigation without energy monitoring.

Buy the Shelly 2PM Gen4 if you need to control two circuits or automate roller shutters, want per-channel energy monitoring, full protection and Zigbee flexibility, and your box has a neutral wire.