Home Energy Management — Common Questions

What's the Difference Between Power and Energy?

People mix these two up all the time, but power and energy describe different things. Power is the rate at which energy moves or converts — the "how fast." Energy is the total that has moved or converted — the "how much."

The unit for power is the watt (W); energy is normally counted in kilowatt-hours (kWh). If it helps, picture a road trip: power is like your speed at any instant, and energy is like the distance you've covered by the end.

Put formally, energy is the integral of power over time. When all you have is a series of sampled power readings, the energy used across a stretch of time has to be estimated numerically from those samples.

Why does any of this matter? Because the Energy dashboard expects entities of the correct type, and feeding it a power sensor where it wants an energy sensor simply won't work.

Turning a Power Sensor Into an Energy Sensor

WoowTech only ever sees a stream of individual power samples, not a smooth, continuous curve — so it can't compute energy exactly from sparse data. What it can do is approximate the integral numerically.

As long as the power value is read often enough — every few seconds is plenty — a method such as a Riemann sum will give a dependable estimate of the energy transferred. In practice, the integration integration handles this for you:

# configuration.yaml
sensor:
  - platform: integration
    source: sensor.workshop_heater_power
    name: Workshop Heater Energy
    unit_prefix: k
    unit_time: h
    method: left
    round: 3

That produces a sensor.workshop_heater_energy entity in kWh that the Energy dashboard can ingest.

Breaking One Meter Into Several Tariffs

If your readings come from a third-party gadget rather than straight off the utility meter or your provider's cloud, WoowTech can still split a single accumulating sensor into the separate rate bands your contract uses. The utility_meter integration lets you declare as many tariffs as you need:

# configuration.yaml
utility_meter:
  household_grid_energy:
    source: sensor.mains_import_energy
    cycle: monthly
    tariffs:
      - daytime
      - nighttime

You then switch the active band with the select.select_option action against the generated select.household_grid_energy entity (for example from an automation tied to your supplier's schedule), and each tariff accumulates independently.

I Don't See the Energy Dashboard

If the Energy entry is missing from your sidebar, the most common reason is that default_config: has been taken out of configuration.yaml. That line pulls in a bundle of integrations and UI pieces, the Energy dashboard among them. Put it back, or if you've deliberately removed it, re-enable the required integrations and interface elements by hand.

A Sensor Won't Appear in the Picker

Symptom

When you try to add a source to the Energy dashboard, the sensor you want isn't in the dropdown.

What to check

Open Settings > Developer tools > States and confirm the entity's attributes:

• device_class — energy or power for electricity, solar, and battery; gas for gas; water for water.
• state_class — measurement for a power sensor; total or total_increasing for accumulating energy/gas/water sensors.
• unit_of_measurement — has to be one of the units accepted for that category, and superscript characters (like the ³ in m³) must match exactly.

Two more things to verify:

• The entity has to live in the sensor domain. If your value sits in something like an input_number, wrap it in a template sensor first:

yaml # configuration.yaml template: - sensor: - name: Pantry Freezer Energy unit_of_measurement: kWh device_class: energy state_class: total_increasing state: "{{ states('input_number.pantry_freezer_kwh') | float(0) }}"

• Finally, open Settings > Developer tools > Statistics and clear up any errors flagged against the entity — a unit mismatch logged there will keep it out of the dashboard.