Shelly Gen4 Smart Switches & Relays: The Hub-Free Approach

Shelly has built a genuinely distinctive niche in the smart home world: tiny, hidden-in-the-wall relays and switches that connect over Wi-Fi directly — no proprietary hub required, no Z-Wave or Zigbee radio, just a small module that fits behind an existing switch or inside a junction box and gives that switch smart capability without changing what's visible on the wall. The newest Gen4 lineup refines that formula with better power monitoring, dry contact support, and a growing family of add-on accessories.

Why Shelly's Approach Is Different

Most smart switches you install are visible — a new switch plate, a new set of buttons or a touchscreen where your old switch used to be. Shelly relays are designed to be invisible: they mount behind the existing switch, inside the wall box or junction box, and let your existing physical switch keep working exactly as it always has while also adding Wi-Fi smart control in parallel. This "invisible retrofit" approach is genuinely useful for households (or landlords) who don't want to change the visible hardware but do want smart control added underneath it.

The Core Gen4 Switch Lineup

Shelly 1 Gen4

Shelly 1 Mini Gen4

Shelly 1PM Gen4

The Shelly 1 Gen4 is the standard entry point — a one-channel relay with dry contact input support, meaning it can accept a signal from an existing physical switch to trigger the relay, preserving normal wall-switch behavior while adding Wi-Fi smart control. The Shelly 1 Mini Gen4 shrinks the same core function into a smaller footprint — critical for tight, crowded junction boxes where a standard-size relay simply won't fit alongside existing wiring.

The Shelly 1PM Gen4 adds real-time power monitoring on top of the same switching capability — useful for tracking actual energy usage on a specific circuit, identifying which devices are drawing unusual power, or building energy-usage automations (like alerting you if a device is drawing power it shouldn't be at 2am).

Compact Relay Options

Shelly 1PM Mini Gen4

The Shelly 1PM Mini Gen4 combines the compact form factor of the Mini line with power monitoring — the right choice when you need both a tight physical fit and energy tracking data, without stepping up to the full-size 1PM Gen4.

Multi-Input Control: Shelly Plus i4

Shelly Plus i4 DC Input Controller

Not every Shelly device is a relay. The Shelly Plus i4 DC Input Controller is a 4-channel input device — it doesn't switch anything itself, but reads up to four separate switch or button inputs and reports their state over Wi-Fi. This is useful for scenarios where you want to capture button presses or switch states from existing hardware to trigger scenes elsewhere in your smart home, without needing a separate relay for every single input point.

RGBW Lighting Control

Shelly Plus RGBW PM

The Shelly Plus RGBW PM drives color-changing LED strip lighting with full RGBW control plus power monitoring — a compact controller for under-cabinet lighting, accent lighting, or any RGBW LED strip project that needs Wi-Fi control without a separate dedicated lighting hub.

Extending Functionality: The Add-On Module

Shelly Plus Add-On Module

The Shelly Plus Add-On Module extends compatible Shelly Plus devices with additional input capability — a way to add extra external sensor or switch inputs to a Shelly relay that's already installed, without replacing the base device.

Who Shelly Fits Best

• Homeowners who want to keep existing switch hardware visible while adding smart control invisibly behind the wall plate
• Tight junction boxes where a standard-size Z-Wave or Wi-Fi switch won't physically fit — the Mini line solves this
• Energy monitoring on specific circuits via the PM (power monitoring) variants
• Households without a Z-Wave/Zigbee hub who prefer direct Wi-Fi connectivity

Quick Reference

FAQ

Q: Do Shelly devices require a hub, like Z-Wave or Zigbee devices do?
A: No — Shelly Gen4 devices connect directly to your home Wi-Fi network, with no separate hub required. They can be controlled via the Shelly app, integrated with voice assistants, or connected to home automation platforms like Home Assistant that support Wi-Fi device integration.

Q: What does "dry contact" mean on the Shelly 1 Gen4?
A: A dry contact input accepts a signal from an existing physical switch without passing line voltage through that connection — essentially reading whether the switch is in the on or off position, which lets your existing wall switch continue to work normally while the Shelly relay does the actual load switching in parallel.

Q: Will installing a Shelly relay behind my existing switch change how that switch looks or feels?
A: No — that's the core design premise. The relay is hidden inside the wall box or junction box; your existing visible switch hardware and its physical feel remain completely unchanged.

Q: Can Shelly devices work if my home Wi-Fi goes down?
A: Since Shelly relies on Wi-Fi rather than a local mesh protocol like Z-Wave, remote/app control and cloud-dependent automations will be affected by a Wi-Fi outage. Local automations configured directly on the device (via Shelly's built-in scripting) can continue to function even without internet access, though this depends on your specific configuration.

Shelly's Gen4 lineup is one of the most flexible ways to add Wi-Fi smart control behind existing switches without changing what's visible on the wall. Call our tech support team to confirm which model fits your junction box space and wiring configuration before you order.