Peak Shaving with Home Assistant: Cut Your Demand Charges

Peak shaving can affect your electricity bill when your tariff charges for measured peak demand. The concept is simple: prevent grid power from spiking above a chosen threshold. Home Assistant can help you monitor and coordinate flexible loads.

Whether you have an EV or controllable appliances, you can test peak-shaving strategies against your own measured peak and tariff. Battery control requires vendor-specific safeguards and is not supplied by the SmartWattFlow dashboard guide.

What Is Peak Shaving?

Peak shaving means reducing your maximum power draw during high-demand periods. Instead of pulling 8 kW from the grid when your EV charger, heat pump, and oven all run simultaneously, you keep consumption below a set limit—say 5 kW.

Why does this matter? Two reasons:

• Demand charges: Some tariffs charge for measured peak demand as well as energy. Check your current network tariff for the exact calculation and minimum billed peak.
• Grid stability: Some countries (Netherlands, Belgium, parts of Germany) are introducing capacity-based tariffs that penalize high peaks. Lower peaks = lower bills.

Strategy 1: Load Shifting (No Battery Needed)

The simplest form of peak shaving: don't run heavy appliances simultaneously. This requires zero hardware investment—just smart scheduling.

Identify Your Peak Creators

Check your energy dashboard for the biggest consumers. Typical culprits:

• EV charger: 3.7-11 kW
• Heat pump: 2-5 kW
• Electric oven: 2-3 kW
• Dryer: 2-3 kW
• Washing machine (heating cycle): 2 kW

Automation: Sequential Appliance Control

This automation prevents the EV charger from running when total household power exceeds a threshold:

# Peak Shaving - Pause EV charging during high demand
alias: "Peak Shaving - EV Pause"
trigger:
  - platform: numeric_state
    entity_id: sensor.grid_power
    above: 4000
    for: "00:01:00"
condition:
  - condition: state
    entity_id: switch.ev_charger
    state: "on"
action:
  - service: switch.turn_off
    target:
      entity_id: switch.ev_charger
  - service: notify.mobile_app
    data:
      title: "Peak Shaving Active"
      message: "EV charging paused - grid power above 4 kW"

Pair this with a matching automation that resumes charging when power drops below 3 kW. The 1 kW gap prevents rapid on/off cycling.

Pausing the charger is the blunt version of this. Because the car is usually the largest and most flexible load in the house, it pays to schedule it properly rather than just interrupt it—our guide to EV smart charging with Home Assistant covers price-aware and solar-surplus charging that keeps your peaks down without you ever hitting the threshold.

Strategy 2: Battery-Based Peak Shaving

If you have a home battery (Tesla Powerwall, BYD, Huawei Luna), you can use it to absorb demand spikes. The battery discharges when grid power exceeds your threshold, keeping your grid draw flat.

The Logic

1. Monitor real-time grid power consumption
2. When grid power exceeds the threshold (e.g., 5 kW), command the battery to discharge
3. The discharge amount equals the difference: if grid is at 7 kW and threshold is 5 kW, discharge 2 kW
4. When grid power drops below threshold, stop battery discharge

# Battery Peak Shaving - Discharge above threshold
alias: "Battery Peak Shaving"
trigger:
  - platform: numeric_state
    entity_id: sensor.grid_power
    above: 5000
condition:
  - condition: numeric_state
    entity_id: sensor.battery_soc
    above: 20  # Keep 20% reserve
action:
  - service: number.set_value
    target:
      entity_id: number.battery_discharge_power
    data:
      value: >
        {{ (states('sensor.grid_power') | int - 5000) | abs }}

Strategy 3: Solar Self-Consumption Optimization

If you have solar panels, peak shaving works in reverse during sunny hours. Instead of exporting surplus to the grid at low feed-in tariffs, use it to pre-charge your battery or pre-heat your home. This reduces afternoon/evening peaks when solar production drops.

The concept: When solar production exceeds consumption, divert energy to scheduled loads (hot water, EV, battery) instead of exporting. Then when evening demand peaks hit, you've already handled those loads.

Setting Your Peak Threshold

Choose the threshold from measurement and safety constraints. Too low can trigger excessive load shedding; too high may not change the billed peak.

How to Test a Threshold

1. Check your energy dashboard for the past month's peak power readings
2. Look at your utility bill for the demand charge component
3. Choose a small, testable reduction from your own measured baseline
4. Monitor through representative conditions and adjust based on comfort, safety, and trigger frequency

Never copy a threshold from another household: the safe target depends on your loads, wiring, device controls, and tariff calculation.

Monitoring Peak Shaving Performance

Create a template sensor to track your daily maximum grid power. This lets you see the direct impact of peak shaving over time:

template:
  - sensor:
      - name: "Daily Peak Power"
        unit_of_measurement: "W"
        state: >
          {{ state_attr('sensor.grid_power', 'max_value')
             | default(states('sensor.grid_power'), true) }}

Track this value over weeks. A successful peak shaving setup should show a clear downward trend in daily peaks, with fewer and smaller spikes above your threshold.

Calculate the Effect from Your Tariff

First confirm how your supplier or network operator bills peak demand. If it uses a linear annual rate, one transparent scenario is (measured current peak − tested target peak) × the published annual rate per kW. If it uses monthly peaks, minimum values, bands, or taxes, reproduce those rules instead.

Compare that annual scenario with all hardware, installation, degradation, and maintenance costs. Existing equipment is not “free,” and a battery payback cannot be inferred from peak reduction alone.