This lesson ties standby, rate plans, PV surplus, and dynamic prices into practical scenarios. I'll also show three levels of action: a plain notification, a semi-automatic suggestion, and a full automation with an override. Plan on about 75 to 90 minutes.

Savings start with observation

Before you write your first payback-aware automation, you need a few days or weeks of data. Without it, you don't know whether standby draw is 5 W or 50 W, whether your PV surplus at noon is 2 kW or 200 W, or whether a dynamic price during a given period is genuinely low relative to your own thresholds and billing rules.

Standby: when to switch off, and when it isn't worth it

Standby is low power draw when a device is technically switched off but still energized. In Lesson 4 you measured standby through an outlet and sent notifications about it. Here we sharpen when that actually makes financial sense.

The rule from Lesson 4 still holds: notification first, an optional auto-shutoff second, with an input_boolean off by default. Standby is a good first automation topic, because it's easy to measure and verify.

Rate plans in plain terms

A rate plan is how you're billed for energy by your utility. Home Assistant can't switch your rate plan for you, but you need to know which one you're on, because it decides whether an automation even makes sense.

PV surplus: when to switch on a device

A PV surplus happens when you're producing more than the home is using and you start exporting to the grid. That's a sensible moment to run a device you'd otherwise have to power from the grid later anyway: a water heater, dishwasher, washing machine, dryer, or EV charger.

To judge a surplus, you need a genuine export signal, or negative grid power with a known sign convention. "PV above 1500 W and low import" alone doesn't mean a surplus: the home could still be buying energy from the grid. The most reliable option is a dedicated export power sensor.

template:
  - binary_sensor:
      - name: "PV Surplus Now"
        unique_id: pv_surplus_now
        icon: mdi:solar-power
        availability: >
          {{ states('sensor.export_power') not in ['unknown', 'unavailable', 'none'] }}
        state: >
          {{ states('sensor.export_power') | float > 1500 }}
        delay_on: "00:10:00"
        delay_off: "00:05:00"

Hysteresis: so the automation doesn't flap every minute

With energy, hysteresis, the gap between your on-threshold and off-threshold, matters a lot. If you switch a device on at 1500 W of surplus and off at the same 1500 W, the automation can flap constantly. It's better to switch on at a higher threshold and only switch off after a longer dip, or at a much lower threshold.

Dynamic pricing: when the price is low, and when it's high

A dynamic wholesale price changes over time, but it isn't automatically the buy price under your own agreement. For decisions about drawing power, use the price coming from your dynamic rate plan, or your own buy-price sensor. A wholesale price can matter for a solar export credit, or when your own plan is genuinely tied to the market.

Dynamic pricing and solar: not every surplus has the same value

This distinction matters. Energy used on-site from your own PV is usually the most valuable to you, because you're not buying it from the grid. Exported energy has a value that depends on your net metering or export-credit arrangement and the current market price. Energy drawn from the grid at a high dynamic price costs more than at a low one.

That's why "switch on the water heater when there's a PV surplus" often makes more sense than "switch on the water heater when the dynamic price is low," if you're already producing at that same time. Use your own energy first, then optimize against the market price.

A simple payback threshold

Before automating a device, do a rough calculation of whether it's worth it. The simple formula from Lesson 3 is enough.

You can keep thresholds in an input_number, so you can adjust them easily without editing the automation.

input_number:
  cheap_price_threshold_per_mwh:
    name: "Cheap Price Threshold"
    min: 0
    max: 400
    step: 1
    unit_of_measurement: "$/MWh"
    icon: mdi:cash-minus
    initial: 60

Three modes: notify, semi-automatic, automatic

Don't jump straight to a full automation. In the energy module we use three levels. Each one requires more trust in the data and more buy-in from the household.

input_boolean as an automation override

Every payback-aware automation should have a kill switch. In Lesson 4 you used an input_boolean as an override for standby auto-shutoff. We apply the same mechanism more broadly here: one switch per scenario, off by default.

input_boolean:
  auto_pv_water_heater:
    name: "Auto: Water Heater on PV Surplus"
    icon: mdi:water-boiler
    initial: false

  auto_price_dishwasher:
    name: "Auto: Dishwasher at a Cheap Price"
    icon: mdi:dishwasher
    initial: false

Payback-aware automation examples

Below are six scenarios. Each starts with a notification. The automatic version requires the input_boolean override to be on. Swap entity names for your own.

1. Water heater on PV surplus (notification)

automation:
  - alias: "Energy: water heater, PV surplus"
    description: "Suggests switching on the water heater during a PV surplus"
    mode: single
    triggers:
      - trigger: state
        entity_id: binary_sensor.pv_surplus_now
        to: "on"
    conditions:
      - condition: state
        entity_id: switch.water_heater
        state: "off"
    actions:
      - action: notify.mobile_app_your_phone
        data:
          title: "PV Surplus"
          message: "Confirmed PV surplus (export). You can switch on the water heater."

2. Water heater on PV surplus (automatic with override)

automation:
  - alias: "Energy: water heater on confirmed PV surplus"
    description: "Controls heating consent only under safe conditions"
    mode: restart
    triggers:
      - trigger: state
        entity_id: binary_sensor.pv_surplus_now
        to: "on"
    conditions:
      - condition: state
        entity_id: input_boolean.auto_pv_water_heater
        state: "on"
      - condition: state
        entity_id: switch.water_heater
        state: "off"
      - condition: numeric_state
        entity_id: sensor.water_heater_temperature
        below: 55
      - condition: time
        after: "08:00:00"
        before: "20:00:00"
    actions:
      - action: switch.turn_on
        target:
          entity_id: switch.water_heater
      - wait_for_trigger:
          - trigger: state
            entity_id: binary_sensor.pv_surplus_now
            to: "off"
            for:
              minutes: 5
          - trigger: numeric_state
            entity_id: sensor.water_heater_temperature
            above: 59
        timeout:
          hours: 2
        continue_on_timeout: true
      - action: switch.turn_off
        target:
          entity_id: switch.water_heater
      - action: notify.mobile_app_your_phone
        data:
          title: "Water Heater"
          message: "Heating cycle finished, or stopped after the surplus ended."

3. Dishwasher at a cheap dynamic price (notification)

automation:
  - alias: "Energy: dishwasher, cheap dynamic price"
    description: "Reminds you about the dishwasher when the price drops below the threshold"
    mode: single
    triggers:
      - trigger: template
        value_template: >
          {{ states('sensor.energy_price_now_per_mwh') | float(9999)
             < states('input_number.cheap_price_threshold_per_mwh') | float(60) }}
        for:
          minutes: 10
    conditions:
      - condition: state
        entity_id: switch.dishwasher
        state: "off"
      - condition: time
        after: "07:00:00"
        before: "22:00:00"
    actions:
      - action: notify.mobile_app_your_phone
        data:
          title: "Cheap Energy"
          message: >
            Price: {{ states('sensor.energy_price_now_per_mwh') }} $/MWh.
            A good moment for the dishwasher.

4. Washing machine on a cheaper overnight rate

automation:
  - alias: "Energy: washing machine, overnight rate"
    description: "Reminds you about the washing machine during the cheaper overnight rate"
    mode: single
    triggers:
      - trigger: time
        at: "22:30:00"
    conditions:
      - condition: state
        entity_id: switch.washing_machine
        state: "off"
    actions:
      - action: notify.mobile_app_your_phone
        data:
          title: "Overnight Rate"
          message: "Cheaper energy now. You can start the washing machine."

5. EV charger: PV or a cheap dynamic price

automation:
  - alias: "Energy: EV charger, PV or cheap dynamic price"
    description: "Suggests charging when there's a PV surplus or a low dynamic price"
    mode: single
    triggers:
      - trigger: state
        entity_id: binary_sensor.pv_surplus_now
        to: "on"
      - trigger: template
        value_template: >
          {{ states('sensor.energy_price_now_per_mwh') | float(9999)
             < states('input_number.cheap_price_threshold_per_mwh') | float(60) }}
    conditions:
      - condition: state
        entity_id: switch.ev_charger
        state: "off"
    actions:
      - action: notify.mobile_app_your_phone
        data:
          title: "EV Charging"
          message: "A good moment to charge: PV surplus or a low dynamic price."

6. Air conditioning: avoid a high buy price

automation:
  - alias: "Energy: air conditioning during a high buy price"
    mode: single
    triggers:
      - trigger: numeric_state
        entity_id: sensor.energy_buy_price
        above: 0.30
      - trigger: state
        entity_id: climate.living_room_ac
        to: "cool"
    conditions:
      - condition: state
        entity_id: climate.living_room_ac
        state: "cool"
      - condition: numeric_state
        entity_id: sensor.energy_buy_price
        above: 0.30
    actions:
      - action: notify.mobile_app_your_phone
        data:
          title: "High Energy Price"
          message: "The air conditioner is running during a high buy-price period."

What not to automate at the start

Common mistakes

Assignment: pick one payback-aware automation

Key takeaways

What's next

In Lesson 8 we'll build a modern energy dashboard: a power flow card, an energy flow view, ApexCharts, and gradient charts. That'll be your everyday panel, showing production, import, export, self-consumption, dynamic pricing, and the effect of your automations all in one place.

If you finish this lesson with one working payback-aware automation, even just as a notification, you've moved from measurement to a real decision. That's the moment Home Assistant starts genuinely saving you money, instead of just showing you numbers.