Isolation

Optocoupler and power isolation keep relay switching spikes and mains faults away from the ESP32. Industrial boards like Waveshare’s add isolated power and RS485, which is far more robust for permanent installs than a bare budget board.

Power Input

Many boards include an AC-DC supply so they run directly from mains; others take 5–30 V DC or more. A wide DC input (up to 60 V on some) suits vehicles, solar systems and 24 V industrial supplies.

Channel Count and Rating

Count your loads and add spares. Check the contact rating (typically 10 A at 250 VAC) and derate for motors, pumps and compressors, which draw large inrush currents; use a contactor for heavy loads.

Connectivity

Wi-Fi and Bluetooth are standard. RS485 lets the board talk Modbus to meters and sensors, Ethernet or PoE gives a reliable wired link, and Matter or Zigbee (on newer Shelly devices) connects to ecosystems without a hub.

Programming and Enclosure

Dev-style boards with USB-C are easiest to program. Budget boards often need a USB-to-serial adapter on a header. For permanent installs, a DIN-rail case or proper enclosure is essential.

Waveshare’s 8-channel version gives you two more relays plus digital inputs, which is useful for reading wall switches, door contacts or float sensors on the same board. Like the 6-channel model, it uses an ESP32-S3 with an isolated RS485 interface and isolation protection, so it suits whole-house lighting circuits, multi-zone irrigation or a small machine controller. It’s rated about 4.8 stars from 13 ratings and was well stocked when we checked, which makes it the practical pick while the 6-channel board is scarce.

For control panels where Wi-Fi isn’t reliable enough, such as a garage, a pump house or a commercial site, this version of Waveshare’s 8-channel board adds a PoE Ethernet port. One network cable can power the board and connect it to Home Assistant or a Modbus TCP system, while the RS485 port talks to field devices. It keeps the same relays, digital inputs and isolation circuits as the Wi-Fi model, and Waveshare supports the Arduino IDE. It has about 5 stars from 9 ratings, with good stock. Our ESP32 Ethernet and PoE guide covers more wired boards.

Sometimes you only need to switch one load: a water heater, a pump or a ventilation fan. Waveshare’s 1-channel ESP32-S3 relay does exactly that in a rail-mount case that clips into a standard DIN-rail enclosure, with a 10 A, 250 VAC relay, RS485 and the same isolation protection as its bigger siblings. Because it’s enclosed, it’s a much tidier and safer choice for a distribution board than an open PCB. Reviews are perfect but few (5 stars from 5 ratings), with 19 in stock.

DORHEA’s 4-channel ESP32 relay board is a popular budget choice for ESPHome and Tasmota projects (about 4.2 stars from 21 ratings). It combines an ESP32-WROOM-32E module with 4 MB of flash, four relays and an onboard AC-DC switching supply that runs from either AC 220 V or DC 5–30 V, plus reset and programmable buttons. All I/O and the UART download port are broken out, so flash it with a USB-to-serial adapter. There’s no isolation beyond the basic relay drivers, so keep it in a proper enclosure and treat the whole board as live when it’s mains powered.

ACEIRMC’s board covers the same ground as the DORHEA model with a wider power input: its onboard supply accepts AC 90–250 V, DC 7–30 V or a direct 5 V feed, so the same board works in 120 V and 230 V countries or from a 12/24 V DC supply. It has an ESP32 module with 4 MB of flash, four 5 V relays and all I/O and UART pins broken out for development. It has about 4.1 stars from 20 ratings. The same caveats apply: no case, limited isolation, and a USB-to-serial adapter needed for flashing. A 2-pack (B0DTK2PB26) is also listed.

When you need eight outputs on a budget, such as for irrigation zones, aquarium equipment or a model railway, DORHEA’s 8-channel ESP32 relay board is the low-cost option (about 4.2 stars from 21 ratings). It uses the ESP32-WROOM-32E and runs from a DC 5–30 V supply, so it pairs well with a 12 V or 24 V power supply and low-voltage loads like solenoid valves. As with all budget relay boards, add your own enclosure and isolation for anything permanent. Only 5 were left when we checked.

This compact 2-channel ESP32 relay board stands out for its DC 5–60 V input range, which covers 12 V vehicles, 24 V industrial supplies and 48 V solar or battery systems without a separate converter (about 4.6 stars from 22 ratings). It has an ESP32 with 4 MB flash, two relays for loads up to AC 250 V or DC 30 V, programmable and reset buttons, and all I/O plus the UART download port broken out. It’s a good fit for switching a camper’s water pump and lights, or a solar system’s load disconnect.

With over 1,200 ratings (about 4.6 stars), the Shelly 1 Gen3 is the most popular smart relay in this guide. It’s a tiny 16 A, single-channel relay with dry contacts that fits behind a light switch or inside a socket box, connects over Wi-Fi and Matter, and doubles as a Bluetooth gateway. Dry contacts mean it can switch a garage door opener, boiler or low-voltage circuit as well as mains lighting. It works locally with Home Assistant, and the Shelly community documents ESPHome flashing for Gen3 devices. This listing is a 4-pack. As with any in-wall device, installation should follow local electrical code.

The Shelly 1 Mini Gen4 shrinks the relay even further for shallow wall boxes and adds Zigbee to Wi-Fi and Matter, so it can join a Zigbee network or work over Wi-Fi with no hub required. Shelly says the Gen4 platform uses an upgraded processor with 8 MB of memory for faster, more reliable operation. It switches loads up to 8 A through dry contacts, which is plenty for lighting circuits and small appliances. It has about 4.5 stars from 840+ ratings.

For a consumer unit or distribution board, the Shelly Pro 1 is a professional-style DIN-rail relay with both LAN and Wi-Fi, a 16 A potential-free contact and a Bluetooth gateway (about 4.6 stars from 443 ratings). Wired Ethernet makes it more dependable than in-wall Wi-Fi relays inside a metal cabinet, and it suits lighting circuits, water heaters and HVAC equipment in homes and small commercial sites. It integrates with Home Assistant, Alexa and Google Home without a hub. Installation in a distribution board must be done by a qualified electrician.

Permanent multi-circuit install?

A Waveshare industrial 6 or 8-channel board with isolation and RS485.

Learning relay control?

The LILYGO T-Relay on 5 V with low-voltage loads.

Behind a light switch?

A Shelly 1 Gen3, or the 1 Mini Gen4 for shallow boxes.

In a DIN-rail panel?

The Waveshare 1-channel in its rail case, or the Shelly Pro 1.

12, 24 or 48 V system?

The 2-channel DC 5–60 V board or the DORHEA 8-channel.

Tight budget, enclosed project?

The DORHEA or ACEIRMC 4-channel boards.

Can I use these boards with ESPHome and Home Assistant?

Yes. Any ESP32 relay board can run ESPHome: each relay becomes a switch entity driven by a GPIO, and Home Assistant discovers the device automatically. Check the board’s documentation for which GPIO drives each relay, and set the relays to restore a safe state (usually off) after a power cut.

Is it safe to switch mains voltage with an ESP32 relay board?

Only when it’s installed correctly: a suitable enclosure, proper fusing, correct wire gauges, separation between mains and low-voltage wiring, and compliance with local electrical codes. If you’re not qualified, have an electrician do the mains side. Certified products like Shelly relays are designed and tested for in-wall installation, which bare dev boards are not.

Can a 10 A relay run a pump or motor?

Small ones, yes, but motors and compressors draw several times their running current at start-up, which wears relay contacts quickly. For pumps, heaters and air conditioners, use the ESP32 relay to switch a properly rated contactor, and fit a snubber or flyback diode on inductive DC loads such as solenoid valves.

What is RS485 used for on these boards?

RS485 is a robust, long-distance serial bus used by Modbus RTU devices such as energy meters, temperature sensors, VFDs and solar inverters. With an RS485 port, the ESP32 can read those devices and switch relays based on their values, for example turning off a load when solar output drops.

How do I program a relay board without USB?

Disconnect all mains power first, then connect a 3.3 V USB-to-serial adapter to the board’s TX, RX and GND pins, hold the programming (IO0) button while resetting, and upload. After the first flash, ESPHome and Arduino OTA updates let you update firmware over Wi-Fi without opening the enclosure.