Bringing the Electricity Grid Into WoowTech
To manage energy at home you really need three things: how much you draw, where that power comes from, and when you use it. The vast majority of households pull electricity from a public grid. A utility meter records what passes through, and your supplier bills you for it. Because the cost of a kilowatt-hour can shift through the day or follow live market rates, knowing your timing matters as much as knowing your total.
Time-of-Day Pricing
A growing number of suppliers no longer charge a flat rate. Instead, the day is carved into pricing windows — typically a Peak band and an Off-Peak band — as a way of nudging customers to move heavy loads to quieter hours. Peak hours line up with the moments when nearly everyone draws power at once, so the price climbs; Off-Peak windows fall when supply is plentiful and demand is light, so the rate drops.
If your contract spreads consumption across more than one rate band, the energy FAQ explains how to break a single meter reading into separate tariff buckets.
Getting the Data Into WoowTech
WoowTech can't track grid usage until it has a live source of meter readings. There are many ways to feed it that data, ranging from off-the-shelf gadgets to fully home-built sensors.
Tapping the Meter Directly
P1 serial port Meters in the Netherlands, Belgium, and Luxembourg expose a P1 port that streams readings in real time. A budget-friendly way to read it is the SlimmeLezer+, an ESPHome firmware device that plugs straight into the port and shows up in WoowTech automatically.
Zigbee Smart Energy profile Some meters in the US, UK, Canada, and Australia speak the Zigbee Smart Energy profile over the air. Going this route usually means using a certified radio and asking your utility to authorize (provision) the device first. The Rainforest Automation Eagle is one reader that exposes a local API.
Counting the meter's blink A lot of meters carry a small LED that pulses once for every fixed unit of energy that passes. WoowTech Glow is an open ESPHome project that watches that LED and turns the blink rate into a consumption figure.
IEC 62056-21 optical interface This standard sends data over an infrared link on the face of the meter. PiggyMeter is a tidy ESPHome-based option that reads it with minimal fuss.
Smart Message Language (SML)
Widespread on German meters, SML can be ingested either through ESPHome directly or through the open-source sml2mqtt bridge, which republishes the values over MQTT.
Camera plus on-device OCR The AI-on-the-Edge project runs on an inexpensive ESP32-CAM, photographs the meter's display, reads the digits locally, and announces itself to WoowTech through MQTT discovery.
Over-the-air radio capture
In the US and Canada many meters broadcast their readings using the AMR/ERT protocols. A cheap RTL-SDR USB receiver paired with the rtlamr decoder can pick those broadcasts up; the rtlamr2mqtt packaging makes the whole thing drop into WoowTech.
Clamp-On Current Sensors
A current transformer (CT) clamp wraps around a live conductor and infers power draw from the magnetic field of the current flowing through it — no electrical contact required. Popular choices:
- Shelly EM — a ready-made unit with a local API and a polished WoowTech integration.
- Roll-your-own — ESPHome supports CT clamp current inputs as well as dedicated metering chips such as the ATM90E32 for a DIY build.
- LeChacal RPICT HATs — boards that sit on a Raspberry Pi, stack for extra channels, cover single- and three-phase setups, and report over MQTT.
Fitting a CT clamp means working inside your consumer unit / breaker panel. Treat this as an electrician's job — in many places a licensed professional is legally required.
Pulling From Your Supplier
A handful of energy companies expose your near-live consumption through an API that WoowTech can read directly, sparing you any extra hardware.
Wiring It Up Manually
If you bring readings in through the MQTT or Template integrations yourself, make sure each sensor carries the right metadata: a device_class, a state_class, and a unit_of_measurement. Without those, the Energy dashboard won't recognize the sensor.
When a Sensor Won't Show Up
Don't see your power or energy entity in the Energy dashboard pickers? The usual culprit is the Recorder — confirm the sensor isn't being excluded from recorded history, since the dashboard relies on stored statistics.
Bringing the Electricity Grid Into WoowTech
To manage energy at home you really need three things: how much you draw, where that power comes from, and when you use it. The vast majority of households pull electricity from a public grid. A utility meter records what passes through, and your supplier bills you for it. Because the cost of a kilowatt-hour can shift through the day or follow live market rates, knowing your timing matters as much as knowing your total.
Time-of-Day Pricing
A growing number of suppliers no longer charge a flat rate. Instead, the day is carved into pricing windows — typically a Peak band and an Off-Peak band — as a way of nudging customers to move heavy loads to quieter hours. Peak hours line up with the moments when nearly everyone draws power at once, so the price climbs; Off-Peak windows fall when supply is plentiful and demand is light, so the rate drops.
If your contract spreads consumption across more than one rate band, the energy FAQ explains how to break a single meter reading into separate tariff buckets.
Getting the Data Into WoowTech
WoowTech can't track grid usage until it has a live source of meter readings. There are many ways to feed it that data, ranging from off-the-shelf gadgets to fully home-built sensors.
Tapping the Meter Directly
P1 serial port Meters in the Netherlands, Belgium, and Luxembourg expose a P1 port that streams readings in real time. A budget-friendly way to read it is the SlimmeLezer+, an ESPHome firmware device that plugs straight into the port and shows up in WoowTech automatically.
Zigbee Smart Energy profile Some meters in the US, UK, Canada, and Australia speak the Zigbee Smart Energy profile over the air. Going this route usually means using a certified radio and asking your utility to authorize (provision) the device first. The Rainforest Automation Eagle is one reader that exposes a local API.
Counting the meter's blink A lot of meters carry a small LED that pulses once for every fixed unit of energy that passes. WoowTech Glow is an open ESPHome project that watches that LED and turns the blink rate into a consumption figure.
IEC 62056-21 optical interface This standard sends data over an infrared link on the face of the meter. PiggyMeter is a tidy ESPHome-based option that reads it with minimal fuss.
Smart Message Language (SML)
Widespread on German meters, SML can be ingested either through ESPHome directly or through the open-source sml2mqtt bridge, which republishes the values over MQTT.
Camera plus on-device OCR The AI-on-the-Edge project runs on an inexpensive ESP32-CAM, photographs the meter's display, reads the digits locally, and announces itself to WoowTech through MQTT discovery.
Over-the-air radio capture
In the US and Canada many meters broadcast their readings using the AMR/ERT protocols. A cheap RTL-SDR USB receiver paired with the rtlamr decoder can pick those broadcasts up; the rtlamr2mqtt packaging makes the whole thing drop into WoowTech.
Clamp-On Current Sensors
A current transformer (CT) clamp wraps around a live conductor and infers power draw from the magnetic field of the current flowing through it — no electrical contact required. Popular choices:
- Shelly EM — a ready-made unit with a local API and a polished WoowTech integration.
- Roll-your-own — ESPHome supports CT clamp current inputs as well as dedicated metering chips such as the ATM90E32 for a DIY build.
- LeChacal RPICT HATs — boards that sit on a Raspberry Pi, stack for extra channels, cover single- and three-phase setups, and report over MQTT.
Fitting a CT clamp means working inside your consumer unit / breaker panel. Treat this as an electrician's job — in many places a licensed professional is legally required.
Pulling From Your Supplier
A handful of energy companies expose your near-live consumption through an API that WoowTech can read directly, sparing you any extra hardware.
Wiring It Up Manually
If you bring readings in through the MQTT or Template integrations yourself, make sure each sensor carries the right metadata: a device_class, a state_class, and a unit_of_measurement. Without those, the Energy dashboard won't recognize the sensor.
When a Sensor Won't Show Up
Don't see your power or energy entity in the Energy dashboard pickers? The usual culprit is the Recorder — confirm the sensor isn't being excluded from recorded history, since the dashboard relies on stored statistics.
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