Comparison of Shelly Plus Addon with Shelly Plus Uni
The Shelly Plus Addon and the Shelly Plus Uni are both used to integrate external sensors into the Shelly system. A comparison of these solutions is always useful if the inputs of the primary host device are not sufficient for recording the sensor data. The functionality can either be extended directly via the plug-on Plus Addon or realised as a completely independent module using the Shelly Plus Uni.
The Shelly Plus AddOn is an add-on board for certain Shelly models (e.g. Shelly Plus 1 or 1PM). It enhances them with additional inputs such as analogue sensors, temperature sensors (DS18B20) or switches. The AddOn itself does not function independently, but expands the functions of the main device.
The Shelly Plus Uni in contrast, is a standalone, universal module. It can directly integrate sensors or switches, control two outputs, and operates entirely over Wi-Fi – without an additional base unit. This makes it suitable for flexible applications where a fixed installation or relays are not required.
Comparison of technical data
| Shelly Plus Addon | Shelly Plus Uni | |
| Appearance |  |  |
| Type | Extension module (attachment) | Stand-alone device |
| Requires host device | Yes (compatible: Shelly Plus 1/1PM, Shelly Plus 2PM, Shelly Plus i4/i4DC) | No (works directly in WlLAN) |
| Power supply | About the host device | 5V DC/9-28V DC |
| Digital inputs | 1 (potential-free or with voltage) | 2 |
| Analogue inputs | 1 (0-10V) | 1 (0-10V / 0-30V) |
| Outputs | None of your own (uses host relay) | 2 potential-free outputs (up to 100mA) |
| Sensors | Up to 5x DS18B20 or 1x DHT22 | Up to 5x DS18B20 or 1x DHT22 |
| Connection type | Is plugged into the Shelly Plus relay | Loose cable ends (strands) |
| Special feature | Safest solution for 230V environments | Extremely small, ideal for DIY & low voltage |
| Documentation | Shelly Plus Add-on Documentation | Shelly Plus Uni Documentation |
Integration of a wide variety of sensors
- Shelly temperature sensor
- Soil moisture sensor
- Motion detector
- Rain sensor
- photoresistor
Decision support
Question
Recommendation
Do you already have a Shelly Plus relay on site?
Plus Addon
Explanation: Utilises the power and WLAN of the existing Shelly. Saves an extra power supply unit, space and an additional IP address in the network.
Do you need to switch a 230V load (e.g. radiant heater)?
Plus Addon
Explanation: Only the add-on can safely switch large loads via the host relay. It also offers an electrically isolated sensor interface.
Do you work with 12V DC or 24V AC?
Plus Uni
Explanation: The Uni is designed for low voltage (e.g. bell transformer). It is extremely flexible and fault-tolerant thanks to its wide voltage range of 9-28V DC.
Do you need to record two separate signals (e.g. 2 contacts)?
Plus Uni
Explanation: While the add-on only has one digital input, the Uni has two. Ideal for monitoring two contacts simultaneously with just one device.
Do you have extremely little space (e.g. behind a circuit board)?
Plus Uni
Explanation: Smaller than half a credit card and without a fixed housing. It fits into small housings where a Shelly with an add-on would be too deep.