How Load Shedding Works in Smart Energy Systems

Rising electricity costs. Solar panels on every second roof. EV chargers, pool pumps, and ducted air conditioning all competing for the same supply. Managing energy in a modern building is no longer simple — and the manual approach doesn't cut it.

Automated load shedding is how smart buildings handle this. It's one of the most effective tools in energy management, and when it's set up properly, it works invisibly — keeping essential systems running while trimming the expensive peaks.

Load shedding isn't about cutting power. It's about making smarter decisions — automatically and instantly — about which loads matter most at any given moment.

What Is Load Shedding?

In building automation, load shedding means automatically turning off or reducing non-critical electrical loads when energy use approaches a defined threshold.

That threshold might be triggered by:

• Solar generation dropping due to cloud cover or time of day
• Battery state-of-charge falling below a safe level
• Grid draw exceeding a demand limit or tariff threshold
• Generator capacity being approached in an off-grid scenario

The system responds in milliseconds — pausing or reducing loads in a defined priority order — and restores them automatically once conditions improve.

How It Actually Works

The logic is straightforward, even if the implementation requires proper programming:

Every step is logged. Facility managers can review exactly when loads were shed, for how long, and what energy was saved — through a dashboard, BMS display, or cloud portal.

Load Priority Tiers

Good load shedding design starts with classifying every circuit by priority. Here's how a typical site is structured:

The exact tiers are configured to suit each site. An aged care facility has very different priorities to a light manufacturing warehouse — and the programming reflects that.

Real-World Applications

Commercial building with solar

A 50-person office with a 30kW rooftop solar array uses load shedding to stay under its agreed network demand limit during cloudy periods. When solar output drops, the system progressively reduces HVAC setpoints and dims non-essential lighting. The result: no demand penalty charges, even on overcast days.

High-end residential with battery

A Gold Coast waterfront home with a 20kWh battery uses load shedding to protect overnight reserves. When battery SOC drops below 25%, pool heating pauses and the EV charger steps down to 6A. The family wakes up with 15% battery still available — rather than zero.

Multi-unit apartment block

Common area circuits — car park lighting, lift lobbies, ventilation fans — are monitored and shed during peak evening demand. The building stays under its NMI limit, avoiding network excess charges that would otherwise be passed to the body corporate.

What We Use to Build It

At Circuit Logic, we implement load shedding using WAGO PLCs, KNX logic blocks, and Modbus-connected meters — depending on the site's existing infrastructure and scale. The tools we typically combine:

• CT clamp sub-metering on each circuit or distribution board
• Solar inverter integration via Modbus or SunSpec
• Battery management system data (SOC, charge/discharge rate)
• WAGO CODESYS logic for threshold evaluation and relay control
• WebVisu dashboards for live monitoring and manual override