In Brief
Electrification is widely misunderstood as simply replacing fossil fuels with electrons. Its true strategic value lies in flexibility. As Australia's grid saturates with variable renewable generation, the value of energy shifts from volume consumed to timing of consumption. This article explores the Sponge Effect: the capacity for transport and industrial heat loads to absorb cheap renewable surpluses, and outlines why organisations that decouple energy demand from the clock will capture significant competitive advantage. The market mechanisms enabling this shift, from flexibility agreements to negative price arbitrage, are emerging but remain underdeveloped.
The Sponge Effect
The central challenge of the energy transition is no longer generation cost. It is dispatchability. Solar is effectively free at noon. Wind is often abundant at 3 AM. The grid’s problem is that demand, traditionally rigid, does not align with this supply.
The Sponge Effect describes the deliberate orchestration of flexible loads to absorb this renewable abundance. Unlike traditional demand response, which turns things off during peaks, the Sponge Effect turns things on during troughs.
energy cost reduction achievable through managed EV charging during renewable surplus versus unmanaged evening peak charging
ITCSAU energy transition analysis, 2025
Two seasonal windows define the opportunity. Midday solar surplus from 10 AM to 3 PM creates the primary absorption window. Overnight wind generation from midnight to 5 AM creates the secondary window. Together, these periods represent the cheapest energy available on the NEM, and the hours when the grid most needs demand to absorb supply.
This capability is rare. Most industrial processes run flat out. Most EV charging happens at 6 PM. The organisations that break these habits transform energy from a fixed cost into a trading asset.
The Two-Season Opportunity
Solar Surplus (10am-3pm)
- Abundant cheap solar creates duck curve valley
- Perfect window for fleet depot charging
- Pre-cool warehouses and commercial buildings
- Thermal storage charges at near-zero cost
Wind Opportunity (12am-5am)
- Strong overnight wind generation
- Second window for industrial base load
- Overnight EV charging at minimal cost
- Negative price intervals increasingly common
Transport Electrification: The Sleeping Giant
Australia’s transport sector is electrifying. AEMO forecasts that EV adoption will add tens of terawatt-hours to annual demand by the 2030s. If this charging is unmanaged, it will stress local distribution networks. One hundred EVs plugging in on a single substation at 6 PM creates a new peak that infrastructure was not designed to handle.
Managed EV charging is the perfect sponge. The vehicles sit idle for predictable hours. The batteries accept charge at controllable rates. The load is deferrable without operational consequence. No other asset class combines these three characteristics at scale.
Depot fleets represent the highest-value opportunity. Buses and delivery vans sit idle for predictable windows. They can charge exclusively during solar soak periods from 10 AM to 2 PM or overnight wind peaks. OCPP-compliant charging infrastructure enables automated scheduling against wholesale price signals, ensuring vehicles charge when energy is cheapest rather than when they return to base.
Destination charging converts carparks into solar sponges. Five hundred cars plugged in at an office park can absorb megawatts of rooftop solar that would otherwise be curtailed. Workplace charging infrastructure designed for managed scheduling captures value that unmanaged Level 2 chargers cannot access.
The financial case is clear. Unmanaged charging triggers peak demand network charges and coincides with the most expensive wholesale price intervals. Managed charging during renewable abundance avoids both costs simultaneously. For a fleet of 50 vehicles, the difference between managed and unmanaged charging can exceed $200,000 annually in energy and network costs, according to published fleet electrification studies.
Vehicle-to-grid capability amplifies the value further. A fleet that charges during solar surplus and exports during evening peak effectively arbitrages the wholesale market, earning revenue from a transport asset during its idle hours. This transforms fleet electrification from a fuel cost decision into an energy market position.
Industrial Heat and Market Mechanics
Electrifying industrial process heat is often dismissed as too expensive. This assumes the industry pays the average wholesale price. Thermal batteries change the equation.
An industrial boiler does not need to run on electricity exactly when the steam is needed. It can heat a thermal mass, whether sand, brick, or molten salt, when electricity is free or negatively priced, and discharge heat as steam throughout the day. This decouples the timing of electricity consumption from heat demand.
In 2024, the NEM experienced record negative price intervals. An electrified boiler with thermal storage could have been paid to consume energy during the day, avoided gas price exposure entirely, and reduced carbon emissions to near zero.
Heat processes below 200 degrees Celsius, which account for a significant share of industrial energy use, can be served by industrial heat pumps or resistive heating with thermal storage. Above this threshold, emerging high-temperature solutions using molten salt or ceramic storage extend the electrification envelope further.
The technology exists. The market design does not.
Most commercial electricity contracts use flat or peak/off-peak pricing. They insulate customers from wholesale volatility. Consequently, customers have no incentive to act as sponges. An organisation with a perfectly flexible load and a flat-rate contract captures zero value from that flexibility.
This is the central market failure. The NEM’s five-minute settlement intervals create genuine price volatility, with wholesale prices regularly ranging from negative $100 to positive $500 per megawatt-hour within a single day. Flexible loads could arbitrage this volatility. Current contract structures prevent them from doing so.
Flexibility agreements are emerging as the market mechanism that bridges this gap. Under these arrangements, retailers share arbitrage value with customers who can verify their load shifting. The customer moves consumption to surplus windows; the retailer captures the wholesale price differential; both benefit. These agreements remain underdeveloped relative to the opportunity, but early adopters are demonstrating 30 to 40% reductions in effective energy costs.
Network tariff reform is equally important. Current demand charges penalise peak consumption but do not reward demand shifting. A tariff structure that values load absorbed during surplus periods would create the financial signal that flexibility agreements alone cannot scale. The Australian Energy Regulator’s ongoing tariff reform process provides the mechanism, but progress has been slow relative to the opportunity.
The OCPP (Open Charge Point Protocol) standard is the technical enabler for transport flexibility. Chargers that comply with OCPP can receive scheduling commands from fleet management or energy trading platforms, enabling automated response to wholesale price signals. For organisations planning fleet electrification, OCPP compliance should be a non-negotiable procurement requirement from day one. Chargers installed without OCPP capability cannot participate in managed charging programs and lock organisations out of flexibility value for the hardware’s operational lifetime.
The Flexibility Infrastructure Gap
The barrier to scaling the Sponge Effect is not technology. It is infrastructure readiness. Most organisations lack the three prerequisites for load flexibility: price-responsive control systems, contractual structures that expose them to wholesale signals, and monitoring infrastructure that verifies their demand shifting.
Building management systems in most commercial facilities cannot respond to five-minute wholesale price intervals. They operate on fixed schedules or manual overrides. Retrofitting automated BMS integration with wholesale price APIs is a capital investment, but one that pays for itself through avoided peak charges within 18 to 24 months for facilities above 500 kW peak demand.
The workforce capability gap compounds the infrastructure gap. Energy procurement teams trained on fixed-price contract negotiation are not equipped to evaluate flexibility agreements, spot exposure strategies, or demand response aggregation offers. Organisations need energy trading literacy alongside traditional procurement capability.
Strategic Execution
For energy sector leaders and large energy consumers, the Sponge Effect demands action across fleet, facilities, and procurement.
Load Flexibility Implementation
| Action | Owner | Timeline | Priority |
|---|---|---|---|
| Map fleet idle windows against renewable generation profiles | Fleet / Operations | Near-term | critical |
| Audit thermal processes below 200°C for electrification potential | Engineering / Sustainability | Near-term | critical |
| Negotiate flexibility or spot-exposed energy contracts | Procurement / Energy | Near-term | high |
| Deploy OCPP-compliant charging infrastructure across all sites | Facilities / IT | Medium-term | high |
| Integrate BMS with wholesale price API for automated demand response | Technology / Facilities | Medium-term | high |
| Evaluate thermal storage for industrial process heat applications | Engineering / Capital Planning | Medium-term | medium |
The electrification of transport and industry is often viewed as a burden on the grid. In reality, it is the grid’s salvation, if managed correctly. The Sponge Effect turns energy consumption into a service that stabilises the network and creates economic value for participants.
Early movers are already demonstrating the model. Organisations with managed fleet charging, flexible industrial processes, and spot-exposed contracts are capturing energy cost advantages that rigid consumers cannot access. These advantages compound as renewable penetration increases and negative price intervals become more frequent.
The grid does not need more baseload demand. It needs intelligent, flexible demand that absorbs renewable abundance and withdraws during scarcity. The organisations that build this flexibility will transform energy from a fixed cost into a strategic asset. Those that electrify without flexibility will simply replace one rigid cost structure with another. The window to build flexibility infrastructure is now, before fleet procurement and contract decisions lock organisations into the next decade of energy economics.
Flexibility is the new efficiency. Organisations that decouple energy demand from the clock will capture the competitive advantage of the next decade.
Questions for Leadership
Do we know our fleet's idle windows and their alignment with renewable generation peaks?
Managed fleet charging during solar surplus or overnight wind transforms EVs from grid burden to grid asset. Without idle window mapping, charging defaults to expensive evening peaks.
Are our energy contracts structured to expose us to spot price signals or flexibility value?
Flat-rate contracts eliminate incentive to shift load. Spot-exposed or flexibility agreements capture value from consuming energy when supply exceeds demand.
Can our building management systems respond automatically to wholesale price signals?
Manual demand response cannot capture five-minute price intervals. Automated BMS integration enables real-time load shifting across HVAC, lighting, and process loads.
What proportion of our industrial heat processes operate below 200°C and could be electrified with thermal storage?
Heat below 200°C can be served by heat pumps or resistive heating with thermal storage, enabling negative price arbitrage unavailable to gas-fired processes.
Have we modelled the financial impact of managed versus unmanaged EV charging across our facilities?
Unmanaged charging triggers peak demand network charges. Managed charging during renewable abundance can reduce energy costs by 40-60% while avoiding infrastructure upgrades.
The Strategic Imperative
The electrification of transport and industry is not merely a decarbonisation strategy; it is a fundamental restructuring of how organisations interact with energy markets. The Sponge Effect represents the next competitive frontier: organisations that reshape consumption to match renewable abundance will capture energy cost advantages that rigid consumers cannot access.
For Australian boards, the strategic implications are immediate. Fleet electrification decisions made today determine whether vehicles charge during expensive peaks or renewable surplus periods for the next decade. Industrial process heat investments lock in either gas price exposure or access to increasingly frequent negative price intervals. Building management systems either respond to price signals automatically or they do not.
The market mechanisms enabling flexible load are emerging but immature. Flexibility agreements, real-time price exposure, and demand response aggregation remain underdeveloped relative to the opportunity. Organisations that invest in load flexibility infrastructure now, including OCPP-compliant charging, thermal storage, and automated BMS integration, will capture value as these markets mature.
The grid does not need more baseload demand. It needs intelligent, flexible demand that absorbs renewable abundance and withdraws during scarcity. The organisations that build this infrastructure will transform energy from a fixed cost into a strategic asset. Those that electrify without flexibility will simply replace one rigid cost structure with another.
Frequently Asked Questions
What is the Sponge Effect in energy systems?
The Sponge Effect describes the deliberate orchestration of flexible electrical loads to absorb renewable energy surpluses rather than curtailing generation. Unlike traditional demand response which reduces consumption during peaks, the Sponge Effect increases consumption during troughs such as midday solar surplus or overnight wind generation, transforming flexible loads like EV charging and thermal storage into grid-balancing assets.
How does managed EV charging reduce grid stress?
Unmanaged EV charging creates concentrated demand spikes when vehicles plug in after work hours, typically during existing peak periods from 5 to 8 PM. Managed charging uses price signals and scheduling algorithms to shift charging to periods of renewable abundance. This distributes load across low-demand periods, reducing infrastructure upgrade requirements and energy costs simultaneously.
What are thermal batteries and how do they enable industrial electrification?
Thermal batteries store heat energy in materials like sand, brick, or molten salt that can be heated using electricity during periods of low or negative wholesale prices. The stored heat is then discharged as process steam or hot water when needed throughout the day. This decouples the timing of electricity consumption from heat demand, enabling industrial facilities to exploit renewable energy abundance without changing production schedules.
What are negative price intervals and how can organisations benefit from them?
Negative price intervals occur in the National Electricity Market when renewable generation exceeds demand, meaning generators must pay to dispatch electricity. Organisations with flexible loads and appropriate contract structures can be paid to consume energy during these periods. Thermal storage, managed EV charging, and water heating are loads that can shift consumption to capture negative price value while maintaining operational requirements.
What market reforms are needed to support the Sponge Effect at scale?
Current commercial electricity contracts predominantly use flat or peak/off-peak pricing that insulates customers from wholesale volatility and eliminates incentives for load flexibility. Scaling the Sponge Effect requires real-time price exposure for flexible loads, standardised flexibility agreements sharing arbitrage value between retailers and customers, and network tariff structures rewarding demand shifting rather than penalising peak consumption.