Smart EV Charging: Save 40% on Electricity Costs

Electric vehicle ownership comes with many benefits, but one challenge that catches many new EV owners off-guard is the impact on their electricity bill. A typical EV can add $50-150 to your monthly energy costs if charged inefficiently. However, with smart automation through Home Assistant, you can dramatically reduce these costs while actually improving your charging experience.

💰 Real Savings Example

One of our community members reduced their EV charging costs from €180/month to €108/month (40% savings) by implementing the automations covered in this guide. Their setup automatically charges during off-peak hours and prioritizes free solar energy when available.

The Problem with Dumb Charging

Most EV owners simply plug in when they get home, typically between 5-7 PM. This is precisely when electricity is most expensive in many markets due to peak demand pricing. Additionally, this charging pattern:

Occurs during the highest-cost time-of-use periods
Wastes free solar energy that could be used for charging
Strains the electrical grid during peak hours
Prevents taking advantage of negative pricing periods
Doesn't coordinate with home battery systems

Smart Charging Fundamentals

Intelligent EV charging optimization focuses on three key principles:

1. Time-Based Optimization

Schedule charging during off-peak hours when electricity rates are lowest. In many European markets, this can mean rates as low as €0.05/kWh at night versus €0.35/kWh during peak hours.

2. Solar-First Charging

Prioritize charging when your solar panels are producing excess energy. This essentially provides "free" charging from your own renewable generation.

3. Grid-Aware Charging

Dynamically adjust charging rates based on grid conditions, pricing signals, and your household's total energy demand.

Prerequisites and Hardware

Before implementing smart charging, you'll need:

Compatible Charger

The foundation of smart charging is a controllable charger. Popular Home Assistant-compatible options include:

Zappi (Recommended): Excellent solar integration, robust Home Assistant support
Wallbox Pulsar Plus: Good value option with API control
EVSE WiFi: DIY-friendly option for technical users
Tesla Wall Connector: Works with Tesla vehicles and increasing third-party support

Energy Monitoring

Essential for optimal charging decisions:

Whole-home energy monitor (Shelly EM, IoTaWatt, etc.)
Solar production monitoring (if applicable)
Smart meter integration for real-time pricing

💡 Pro Tip

If you're planning to install solar panels, consider doing so before implementing smart EV charging. The combination provides the highest savings potential and fastest return on investment.

Basic Time-of-Use Charging

Let's start with a simple automation that charges your EV during off-peak hours. This alone can save 20-30% on charging costs.

Setting Up Rate Periods

First, define your utility's rate periods:

# configuration.yaml
input_select:
  electricity_rate_period:
    name: "Current Rate Period"
    options:
      - "Peak"
      - "Shoulder"
      - "Off-Peak"
    initial: "Peak"

sensor:
  - platform: template
    sensors:
      current_electricity_rate:
        friendly_name: "Current Rate"
        unit_of_measurement: "€/kWh"
        value_template: >
          {% set period = states('input_select.electricity_rate_period') %}
          {% if period == 'Peak' %}
            0.31
          {% elif period == 'Shoulder' %}
            0.18
          {% else %}
            0.09
          {% endif %}
            

Rate Period Automation

# automations.yaml
- alias: "Set Off-Peak Rate"
  trigger:
    - platform: time
      at: "22:00:00"
  action:
    - service: input_select.select_option
      target:
        entity_id: input_select.electricity_rate_period
      data:
        option: "Off-Peak"

- alias: "Set Peak Rate"
  trigger:
    - platform: time
      at: "07:00:00"
  action:
    - service: input_select.select_option
      target:
        entity_id: input_select.electricity_rate_period
      data:
        option: "Peak"

- alias: "Set Shoulder Rate"
  trigger:
    - platform: time
      at: "14:00:00"
  action:
    - service: input_select.select_option
      target:
        entity_id: input_select.electricity_rate_period
      data:
        option: "Shoulder"
            

Smart Charging Automation

- alias: "Smart EV Charging Control"
  trigger:
    - platform: state
      entity_id: input_select.electricity_rate_period
    - platform: state
      entity_id: device_tracker.my_ev
      to: "home"
    - platform: numeric_state
      entity_id: sensor.ev_battery_level
      below: 80
  condition:
    - condition: state
      entity_id: device_tracker.my_ev
      state: "home"
    - condition: numeric_state
      entity_id: sensor.ev_battery_level
      below: 80
  action:
    - choose:
        - conditions:
            - condition: state
              entity_id: input_select.electricity_rate_period
              state: "Off-Peak"
          sequence:
            - service: switch.turn_on
              entity_id: switch.ev_charger
            - service: notify.mobile_app
              data:
                title: "EV Charging Started"
                message: "Charging at off-peak rate (€{{ states('sensor.current_electricity_rate') }}/kWh)"
        - conditions:
            - condition: state
              entity_id: input_select.electricity_rate_period
              state: "Peak"
          sequence:
            - service: switch.turn_off
              entity_id: switch.ev_charger
            - service: notify.mobile_app
              data:
                title: "EV Charging Paused"
                message: "Waiting for off-peak rates to resume charging"
      default:
        - service: switch.turn_on
          entity_id: switch.ev_charger
            

Solar-Integrated Charging

If you have solar panels, you can achieve even greater savings by prioritizing solar charging. This approach can provide essentially free charging during sunny days.

Solar Surplus Calculation

sensor:
  - platform: template
    sensors:
      solar_surplus:
        friendly_name: "Solar Surplus"
        unit_of_measurement: "W"
        value_template: >
          {% set solar_production = states('sensor.solar_power')|float %}
          {% set house_consumption = states('sensor.house_power')|float %}
          {% set surplus = solar_production - house_consumption %}
          {{ surplus if surplus > 0 else 0 }}
      
      ev_charging_from_solar:
        friendly_name: "EV Charging from Solar"
        unit_of_measurement: "%"
        value_template: >
          {% set ev_power = states('sensor.ev_charger_power')|float %}
          {% set solar_surplus = states('sensor.solar_surplus')|float %}
          {% if ev_power > 0 %}
            {{ ((solar_surplus / ev_power) * 100)|round(0)|int if ev_power <= solar_surplus else 0 }}
          {% else %}
            0
          {% endif %}
            

Dynamic Solar Charging

- alias: "Solar-First EV Charging"
  trigger:
    - platform: state
      entity_id: sensor.solar_surplus
    - platform: state
      entity_id: device_tracker.my_ev
      to: "home"
  condition:
    - condition: state
      entity_id: device_tracker.my_ev
      state: "home"
    - condition: numeric_state
      entity_id: sensor.ev_battery_level
      below: 85
    - condition: sun
      after: sunrise
      before: sunset
  action:
    - choose:
        # High solar surplus - charge at full rate
        - conditions:
            - condition: numeric_state
              entity_id: sensor.solar_surplus
              above: 5000
          sequence:
            - service: number.set_value
              target:
                entity_id: number.ev_charger_current
              data:
                value: 32
            - service: switch.turn_on
              entity_id: switch.ev_charger
        
        # Medium surplus - reduce charging rate
        - conditions:
            - condition: numeric_state
              entity_id: sensor.solar_surplus
              above: 2000
              below: 5000
          sequence:
            - service: number.set_value
              target:
                entity_id: number.ev_charger_current
              data:
                value: 16
            - service: switch.turn_on
              entity_id: switch.ev_charger
        
        # Low surplus - minimum charging
        - conditions:
            - condition: numeric_state
              entity_id: sensor.solar_surplus
              above: 1400
              below: 2000
          sequence:
            - service: number.set_value
              target:
                entity_id: number.ev_charger_current
              data:
                value: 6
            - service: switch.turn_on
              entity_id: switch.ev_charger
      
      # Insufficient surplus - stop charging (unless off-peak)
      default:
        - condition: not
          conditions:
            - condition: state
              entity_id: input_select.electricity_rate_period
              state: "Off-Peak"
        - service: switch.turn_off
          entity_id: switch.ev_charger
            

💡 Advanced Tip

Consider implementing a "learning" algorithm that tracks your driving patterns and adjusts charging schedules based on historical departure times and required charge levels. This prevents situations where you need to leave but the car isn't sufficiently charged.

Advanced Features

Dynamic Pricing Integration

For markets with real-time pricing, integrate live electricity rates:

# Add Nordpool integration for dynamic pricing
sensor:
  - platform: nordpool
    region: "DE"
    currency: "EUR"
    
  - platform: template
    sensors:
      cheapest_hours_today:
        friendly_name: "Cheapest 4 Hours Today"
        value_template: >
          {% set prices = state_attr('sensor.nordpool_kwh_de_eur_3_10_021', 'raw_today') %}
          {% set sorted_prices = prices | sort(attribute='value') %}
          {{ sorted_prices[:4] | map(attribute='hour') | list }}
            

Emergency Override

Always include manual overrides for emergency situations:

input_boolean:
  ev_emergency_charge:
    name: "Emergency EV Charge"
    icon: mdi:car-emergency

automation:
  - alias: "Emergency EV Charge Override"
    trigger:
      - platform: state
        entity_id: input_boolean.ev_emergency_charge
        to: "on"
    action:
      - service: switch.turn_on
        entity_id: switch.ev_charger
      - service: number.set_value
        target:
          entity_id: number.ev_charger_current
        data:
          value: 32
      - delay: "02:00:00"  # Auto-disable after 2 hours
      - service: input_boolean.turn_off
        entity_id: input_boolean.ev_emergency_charge
            

Battery Integration

If you have a home battery system, coordinate charging to maximize efficiency:

- alias: "Coordinated Battery and EV Charging"
  trigger:
    - platform: state
      entity_id: sensor.battery_soc
    - platform: state
      entity_id: input_select.electricity_rate_period
  condition:
    - condition: state
      entity_id: device_tracker.my_ev
      state: "home"
  action:
    - choose:
        # If battery is full and rates are cheap, charge EV
        - conditions:
            - condition: numeric_state
              entity_id: sensor.battery_soc
              above: 95
            - condition: state
              entity_id: input_select.electricity_rate_period
              state: "Off-Peak"
          sequence:
            - service: switch.turn_on
              entity_id: switch.ev_charger
        
        # If battery is low, prioritize battery charging
        - conditions:
            - condition: numeric_state
              entity_id: sensor.battery_soc
              below: 20
          sequence:
            - service: switch.turn_off
              entity_id: switch.ev_charger
            

Monitoring and Optimization

Create a dashboard to track your charging efficiency and savings:

# Dashboard configuration
type: vertical-stack
cards:
  - type: horizontal-stack
    cards:
      - type: entity
        entity: sensor.ev_battery_level
        name: "EV Battery"
      - type: entity
        entity: sensor.current_electricity_rate
        name: "Current Rate"
      - type: entity
        entity: sensor.ev_charging_from_solar
        name: "Solar Charging"
  
  - type: history-graph
    entities:
      - sensor.ev_charger_power
      - sensor.solar_surplus
    hours_to_show: 24
  
  - type: statistics-graph
    entities:
      - sensor.daily_ev_charging_cost
    days_to_show: 30
    stat_types:
      - mean
      - min
      - max
            

Measuring Your Savings

Track the effectiveness of your smart charging setup:

sensor:
  - platform: template
    sensors:
      monthly_ev_charging_savings:
        friendly_name: "Monthly EV Charging Savings"
        unit_of_measurement: "€"
        value_template: >
          {% set kwh_charged = states('sensor.monthly_ev_energy')|float %}
          {% set peak_rate = 0.31 %}
          {% set actual_cost = states('sensor.monthly_ev_cost')|float %}
          {% set peak_cost = kwh_charged * peak_rate %}
          {{ (peak_cost - actual_cost)|round(2) }}
      
      ev_charging_efficiency:
        friendly_name: "Charging Efficiency"
        unit_of_measurement: "%"
        value_template: >
          {% set solar_kwh = states('sensor.monthly_ev_solar_charging')|float %}
          {% set total_kwh = states('sensor.monthly_ev_energy')|float %}
          {{ ((solar_kwh / total_kwh) * 100)|round(1) if total_kwh > 0 else 0 }}
            

Troubleshooting Common Issues

Charger Not Responding

Verify WiFi connectivity and Home Assistant integration status
Check for firmware updates on your charger
Ensure proper electrical installation and grounding
Test manual control through the charger's native app

Inconsistent Solar Charging

Verify solar production sensors are accurate
Check that cloud conditions aren't causing rapid switching
Implement hysteresis in your automations to prevent oscillation
Consider weather forecasting to predict solar production

Rate Period Misalignment

Verify your utility's actual rate schedule (they can change)
Account for daylight saving time transitions
Consider regional variations in rate periods
Implement fallback logic for holiday rate schedules

🎯 Optimization Results

After implementing these strategies, typical users see:

30-40% reduction in EV charging costs
60-80% of charging powered by solar (when available)
Reduced grid strain during peak hours
Extended battery life through optimized charging patterns

Future Enhancements

As your system matures, consider these advanced features:

Machine Learning: Implement predictive algorithms based on driving patterns
Vehicle Integration: Direct communication with your EV for battery status and scheduling
Community Coordination: Participate in demand response programs
Multi-Vehicle Management: Optimize charging across multiple EVs
Carbon Optimization: Charge when grid carbon intensity is lowest

Smart EV charging is one of the most impactful home automation projects you can implement. The combination of significant cost savings, environmental benefits, and improved convenience makes it an essential component of any smart home energy strategy.

⚠️ Safety Reminder

Always follow local electrical codes and regulations when installing EV charging equipment. Have a qualified electrician verify your installation, especially for high-amperage chargers. Never modify charging equipment beyond manufacturer specifications.