SONOFF S31 WiFi Smart Plug Review: Energy Monitoring on a Budget
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ScoredYou don't need a full smart home system to figure out which appliance is quietly wrecking your electric bill. You need one plug and an app. The SONOFF S31 is a WiFi-connected outlet plug that adds remote control and energy monitoring to whatever you plug into it — a lamp, a space heater, a window AC unit, a fish tank pump, whatever's eating your power.
What It Is
The SONOFF S31 is a compact smart plug that sits between your device and the wall outlet, giving you app-based (and often voice-based) control over anything with a standard plug. What sets it apart from the most basic smart plugs is energy monitoring — it tracks how much power the connected device is drawing in real time, so you can see what's actually costing you money instead of guessing.
It connects over WiFi directly, no separate hub required, which keeps setup simple and cost down.
Who It's For
This is squarely a starter or budget-add-on product. It makes sense for:
- Someone dipping a toe into smart home gear for the first time who isn't ready to commit real money
- Anyone who wants to know exactly how much their space heater, mini fridge, or gaming PC costs per month
- People building out a multi-plug smart home setup who need extra outlets without blowing the budget
- Renters or apartment dwellers who want smart control without wiring or a hub investment
It's not for anyone who needs heavy-duty switching for high-draw appliances beyond what a standard plug handles, or buyers who specifically want a hub-based ecosystem like a full Zigbee or Z-Wave setup.
Key Features & Specs
- WiFi connectivity — no separate smart hub needed
- Real-time energy monitoring — track wattage and estimated usage/cost over time
- Remote app control — turn devices on/off from anywhere with a connection
- Compact single-outlet plug design — fits a standard wall outlet without fully blocking the second socket
- Typically compatible with major voice assistants for hands-free control (verify current compatibility on the listing before buying)
Pros
- Genuinely useful energy monitoring at a price point that's hard to find elsewhere
- No hub purchase required, keeping total cost of entry low
- Simple enough for a first-time smart home buyer to set up without a headache
- Easy add-on to an existing smart home setup without straining a budget
Cons
- Priced well below the typical smart home category, which shows up as basic build quality and a no-frills app rather than a polished flagship feel
- Single outlet means you'll need multiples to monitor more than one or two devices
- WiFi-direct setup adds another device competing for your router's bandwidth compared to hub-based systems
- Energy monitoring on budget plugs like this is "good enough for spotting trends," not lab-grade precision
The SONOFF S31 earns its spot for one reason: it makes energy monitoring cheap enough to actually try. It won't impress you with premium materials or a slick app, and the tradeoffs are real — single outlet, basic build, WiFi-only. But for the price, it does exactly what it claims: remote control plus a legitimately useful window into your power usage, no hub required.
If you want to know where your electricity bill is actually going before you invest in anything fancier, start here.
https://www.amazon.com/dp/B08TNF4835?tag=thebenchtest-20&tag=thebenchtest-20
