plug

SONOFF S31

budget local: excellent Wi-Fi

Price: budget band last checked Mar 22, 2026
HA fit: excellent
Works offline: yes
Setup: advanced
Hub needed: no

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SONOFF S31 smart plug with energy monitoring

Quick verdict

The S31 is the cheapest path to energy monitoring smart plugs that actually work locally. Flash it with Tasmota or ESPHome and you've got a fully local plug with power tracking. Stock firmware is cloud-dependent, so plan on flashing — it's easy and well-documented.

Standout: Budget energy-monitoring smart plug that is easily flashable to Tasmota for fully local control.

Notes last checked Mar 22, 2026.

Compatibility snapshot

Home Assistant excellent

Apple Home none

Google Home okay

Alexa okay

Works offline yes

Setup advanced

Extra hub needed no

Power plug-in

Local control facts

Home Assistant: tasmota integration, Local Push (home-assistant.io, checked Sep 10, 2026)

Why it stands out

energy monitoring built in — track power usage per device
easily flashable to Tasmota or ESPHome for fully local control
compact form factor that does not block adjacent outlets

Reasons to hesitate

stock eWeLink firmware is cloud-dependent — flashing is recommended
flashing requires opening the case or using a serial adapter
no Matter or Thread support

Best for

Home Assistant tinkerers who want cheap energy-monitoring plugs with Tasmota
anyone comfortable flashing firmware for the best local-control smart plug value

Avoid if

you want plug-and-play local control without flashing firmware
you are not comfortable opening devices or flashing custom firmware

Privacy and local-control notes

Flashable to Tasmota or ESPHome for fully local, cloud-free operation. Stock firmware uses eWeLink cloud.

Home Assistant support: supported · integration path: Tasmota / ESPHome / eWeLink.

Built with ESPHome - see the ESPHome guide for Home Assistant →

Buying reality check

Price notes: One of the cheapest energy-monitoring smart plugs available. Incredible value when flashed to Tasmota.

Compare side by side: see plug comparisons →

Verified against

The compatibility notes above have not been through the source audit yet. The manufacturer's page is here; the notes were last checked Mar 22, 2026.

Spotted something wrong? Report an error on this page and I will check it against the source and fix it.

Buying guide for this category

Still deciding between products? Start with the broader category guide.

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