- Introduction
- Why Use Smart Relays in Off-Grid Systems?
- Recommended Devices
- Conclusion
Introduction
Wi-Fi AC plugs are available in many brands and can control almost anything that plugs into a standard home AC outlet from anywhere using Wi-Fi, but what about DC devices?
I was recently asked by a customer how he could control a DC-powered device remotely over the internet, a device that itself relies on an internet connection to function. The challenge was that when his Victron Cerbo lost connection, he could reboot the modem using a WiFi-controlled AC plug, but he couldn’t reboot the Cerbo since it runs on DC power.
That question got me thinking about some of the DC control setups I’ve installed in the past. While a few worked, they were often unreliable or “flaky.” So I went searching for something better, a dependable relay device that could handle DC control, integrate with automation systems, and be managed remotely. That’s when I came across the Shelly Plus 1, a well-built smart relay that supports 24–240V AC/DC input, making it ideal for solar setups. It’s WiFi-enabled, app-controlled, and well-reviewed for stability and ease of integration.
Why Use Smart Relays in Off-Grid Systems?
Before smart relays came along, load management in off-grid systems was mostly manual. You’d either turn devices on and off yourself or build the system large enough to handle the worst-case demand. The problem with that approach is it often leads to wasted energy, oversized systems, and no real flexibility when power is limited.
Smart relays change that completely.
They allow your system to automatically manage when and how loads operate. For example:
- Load-shedding / priority control: Non-essential loads can automatically turn off when battery voltage or state of charge drops too low, protecting your batteries from deep discharge.
- Scheduled control: Certain loads, like a water pump, can be programmed to run only when solar production is highest, usually in the middle of the day.
- Remote control & monitoring: You can turn devices on or off remotely through WiFi, Bluetooth, or Zigbee, and even see their live status from anywhere.
- Safety & protection: Smart relays can disconnect loads if there’s an overcurrent, low voltage, or other fault condition, adding another layer of system protection.
Many solar equipment manufacturers now recommend using programmable relays, load-shedding controllers, or smart inverters to actively manage energy use and prevent overloads.
In fact, relay modules are often used in solar systems specifically to switch loads on or off based on the battery’s charge level, current flow, or other system conditions, helping everything work more efficiently and reliably.
Recommended Devices
Based on recent testing and feedback, the Shelly Plus 1 stands out as a strong choice. It’s compact, affordable, and compatible with both AC and DC voltage systems, including 12V, 24V, and 48V battery banks when used within its rated range.
Other notable options worth exploring include:
- Sonoff 4CH Pro R3 – Great for multi-load management, WiFi or RF controlled, with independent channel timers.
- SRNE Smart Relay Modules – Designed for solar applications and can be integrated with charge controllers.
- Victron GX Relay / Smart Relay Integration – For those already in the Victron ecosystem and wanting deeper system logic control.
Conclusion
I’ve tested the Shelly Plus 1, and it works great so far as I continue experimenting with different control setups. Once we connect this device to my customer’s system, I plan to share an update on how it performs over time.
Smart relays are quickly becoming an essential part of modern off-grid solar design. Whether you’re rebooting a DC device like a Cerbo remotely, optimizing loads to run during peak solar hours, or simply adding smarter protection to your setup, automation brings convenience, efficiency, and reliability together.
As systems get more advanced, the ability to remotely monitor, control, and adapt will be the difference between something that simply works, and something that works perfectly.
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