Shelly devices: what the models mean and how to use them in Optimaatti

Shelly is a smart-home ecosystem with switches (relay/dimmer), meters (energy), and sensors. In Optimaatti, Shelly is essentially the control and measurement interface: Optimaatti decides when a device should run, and Shelly executes the switching.

In this article:

• what different Shelly model names mean
• which use cases different devices fit best
• how to connect Shelly devices to Optimaatti (MQTT)
• what to consider for reliability and safety

1) Quick glossary of Shelly model names

Shelly names usually include a few key parts. Once you understand them, you can often pick the right model in the store.

Plus vs Pro

• Shelly Plus: consumer-focused, Wi‑Fi, a solid default choice for homes.
• Shelly Pro: typically DIN-rail for the electrical cabinet, often Ethernet support and more “professional” form factor.

Optimaatti works with both using the same principle: connect via MQTT and control using rules.

1, 2, 4… (number of channels)

The number often indicates how many outputs you can switch:

• 1: one output
• 2: two outputs
• 4: four outputs

If you control two separate loads (two heating circuits, two lighting groups), a 2-channel model can be a good fit.

PM and EM (measurement)

• PM: “Power Measurement” — the device measures power/energy on the controlled output.
• EM / 3EM: separate energy meters. 3EM usually means three-phase measurement.

Measurement is especially useful in Optimaatti:

• better cost analysis and savings reports
• you see what automation actually does

Plug / Plug S

A Shelly Plug is an easy way to start:

• no electrical installation required (as long as the load is suitable)
• often includes energy metering

Good targets: water heater (if plug-connected), circulation pump, dryer, portable heaters.

2) What does Shelly do in Optimaatti?

Optimaatti is the “brain”, Shelly is the “hands”:

• Optimaatti fetches electricity prices and makes decisions based on rules / predictive control (MPC)
• Shelly executes control: on/off (and sometimes dimming) and reports state back

Typical Optimaatti usage:

• price rules: turn on when price is below a threshold or during the cheapest hours
• schedule rules: force on/off at specific times
• temperature rules: turn heating on/off based on a sensor threshold
• predictive control (MPC): predictive control that adapts heating to price and comfort
• offline scheduling: schedules can be stored on the device to keep working during outages

3) How to connect Shelly to Optimaatti (MQTT)

Optimaatti uses MQTT to connect devices. Think of MQTT as a message bus where:

• Shelly publishes state and measurements
• Optimaatti publishes control commands

Step 1: get MQTT credentials from Optimaatti

In the app you’ll find the MQTT host, port, username and password. Use them exactly.

Step 2: enable MQTT in Shelly

Open the Shelly web UI (on your LAN) and:

• enable MQTT
• enter Optimaatti host/port/user/password
• save and confirm the device connects

Step 3: verify the device appears in Optimaatti

Once MQTT works, the device shows up in your device list. Then you can:

• name it clearly
• set its usage type (heating / lighting / other)
• create your first rule

4) How do I choose the right Shelly model?

A few practical rules of thumb.

Water heater

• If you only need on/off: a 1-channel relay (Plus/Pro) is usually enough.
• If you want consumption data: choose a PM model or add separate metering.

Underfloor heating / electric radiators

• Reliability is important, and temperature data helps.
• A common setup is:
  • a relay (Shelly)
  • a temperature sensor (Shelly sensor or another) + temperature rule / predictive control (MPC)

Lighting

• On/off is often enough.
• For dimming you need a dimmer model.

Whole-home consumption and main fuse

• For measuring whole-home power or per-phase power: EM/3EM.
• This helps you understand how automation impacts overall demand.

5) What does “channel/output” mean in Optimaatti?

Many Shelly devices have multiple outputs. In Optimaatti:

• a device may appear as one device, but has multiple controllable outputs
• rules can target a specific output

If you control two separate loads with one 2-channel Shelly, make sure rules target the correct channel.

6) Reliability and safety

• Electrical work should be done by a professional. Large loads and incorrect installation can be a fire risk.
• Use offline schedules when possible: the device follows the schedule even if the internet drops.
• Use strong, unique credentials. Don’t share or hardcode MQTT credentials.
• Keep firmware updated for security and stability.

7) How does Shelly show up in Optimaatti reports?

When the device has energy metering:

• Cost analysis can compute consumption and savings more accurately
• Device state history helps you see when the device was on and how prices/rules affected it

If a device is only a relay without metering, control still works, but reporting is more limited.

Summary

Shelly devices are a key building block in Optimaatti: they turn automation into real-world control. If you pick the right model (channels, metering, installation format) and connect it via MQTT, you get:

• automatic price rules and schedules
• temperature-based control
• predictive control (MPC) (if enabled)
• reporting (especially with metering)

Next step: connect your first Shelly and create a simple rule. When the basics work, you can add predictive control (MPC) and fine-tune pricing/VAT settings so reports match your contract.