A reliable electricity system must meet both the minimum ‘base’ demand that is always present and the additional ‘peak’ demand that occurs at certain times. Different energy sources have different characteristics in terms of how well they can meet these needs.
Power demand (MW)
Peak | ████
| ██████████
Inter | ██████████████
| ████████████████████
Base |_██████████████████████████
0 6 12 18 24 Time (hours)
| Source | Suitable for base load? | Why |
|---|---|---|
| Coal | Yes (traditional) | Continuous, controllable output; slow to ramp up/down |
| Nuclear | Yes | Very high capacity factor; continuous; expensive to start/stop |
| Geothermal | Yes | Continuous natural heat source |
| Hydroelectric (large dams) | Yes (if sufficient water) | Controllable; can operate continuously |
| Biomass/biogas | Yes | Controllable combustion |
| Wind | No | Variable; cannot be predicted reliably |
| Solar PV | No | Only during daylight; variable |
| Source | Suitable for peak load? | Why |
|---|---|---|
| Natural gas (OCGT) | Excellent | Can start in minutes; highly flexible |
| Pumped hydro | Excellent | Very fast response; stores energy |
| Battery storage | Excellent | Millisecond response; limited duration |
| Demand response | Yes | Reduce consumption instead of adding supply |
| Coal | Poor | Takes 8+ hours to start; inflexible |
| Nuclear | Poor | Very inflexible; not designed for rapid cycling |
Individual-scale strategies:
- Rooftop solar PV: Generates electricity during daylight hours (reduces grid demand)
- Home battery storage (e.g. Tesla Powerwall): Stores solar for evening use; reduces peak demand on the grid
- Smart meters and time-of-use pricing: Incentivise shifting high-energy activities (dishwasher, washing machine) to off-peak times
- Energy efficiency: Reduce total consumption — best ‘source’ of supply is energy not used
- Heat pumps: More efficient than resistive heating; reduce peak demand on cold winter mornings
Grid-scale strategies:
- Pumped hydro storage (e.g. Snowy 2.0): Large-scale energy storage; 2,000 MW capacity; can supply peak demand for ~7 days
- Grid-scale battery storage: Fast response (within milliseconds); suitable for short-duration peaks
- Interconnectors: Transmit power between regions to balance supply and demand across distances
- Demand response programs: Industrial users (smelters, water treatment) agree to reduce consumption during peak events in exchange for payment
- Virtual power plants (VPPs): Aggregate thousands of rooftop solar + battery systems into a coordinated resource
- Renewable + storage combinations: Wind and solar with battery or pumped hydro can together replicate base load reliability
As electrification of transport, heating and industry accelerates:
- Total electricity demand will increase (EVs, heat pumps, electrolysers for hydrogen)
- Pattern of demand will shift (overnight EV charging; flat industrial electricity loads)
- Variable renewable generation will dominate → greater need for storage and grid flexibility
Australia’s AEMO (Australian Energy Market Operator) projects that meeting reliability and emissions targets requires:
- Massive increase in renewable capacity (solar, wind, offshore wind)
- ~5× current grid-scale storage capacity by 2030
- Improved transmission interconnectors between states
VCAA FOCUS: Distinguish clearly between base load (continuous, reliable) and peak load (high demand, short duration, rapid response needed). Relate specific energy sources to their suitability for each role. Note that the transition to renewables requires addressing the variability challenge — through storage, interconnection and demand management.