Charge the fleet without exceeding the connection
Twenty buses return with an overnight charging requirement. Buying faster chargers will not remove the site's import constraint; the operator needs a feasible schedule by departure time.
Permanent case linkYour task
Build a feasible charging schedule, price it and stress-test the available connection capacity.
Your role
Fleet-energy analyst comparing charging schedules
Practice data & worked solution
Energy requirement meets a power ceiling
Original synthetic two-block night. Twenty identical buses each need 120 kWh stored by 06:00. Grid-to-battery efficiency 90%. All vehicles are available throughout; chargers can share load continuously with adequate individual ratings. The 600 kW connection limit includes the fixed 100 kW base load. Prices are energy-only; no demand charges, taxes or battery degradation.
| Block | Hours | Connection limit kW | Other site load kW | Price AUD per kWh |
|---|---|---|---|---|
| 22:00–02:00 | 4 | 600 | 100 | 0.12 |
| 02:00–06:00 | 4 | 600 | 100 | 0.25 |
Your analysis
- Calculate required battery energy and grid energy. Check whether the cheapest block can supply it all.
- Allocate as much charging as possible to the cheap block. Compare charging-only cost with a flat eight-hour schedule.
- Reduce the connection limit to 400 kW in both blocks. Quantify the battery-energy shortfall and test an extra hour at the same available charging power.
Worked solution
Power and energy
The buses need 2,400 kWh stored, requiring 2,400/0.90 = 2,666.67 kWh at the grid. Charging headroom is 500 kW. The four cheap hours supply at most 2,000 kWh, so 666.67 kWh must be bought later. Do not apply the 90% efficiency twice.
A feasible low-cost schedule
Charge at 500 kW for the first block and 166.67 kW for the second. Charging-only cost is 2,000 × 0.12 + 666.67 × 0.25 = A$406.67. A flat 333.33 kW charging schedule costs A$493.33, so the saving is A$86.67. Base-load cost is excluded from both comparisons and does not change.
Reduced connection
A 400 kW limit leaves 300 kW for charging. Eight hours supply 2,400 kWh from the grid and 2,160 kWh to batteries, a 240 kWh shortfall. The missing 266.67 grid kWh needs 0.889 extra hours at 300 kW. An extra hour is sufficient only if vehicles, staffing, network permission and departure times allow it.
Review your response
- Boundary: site import includes non-charging load.
- Schedule: each block respects power and departure constraints.
- Cost: compare like-for-like charging energy, not inconsistent site totals.
- Transfer: quantify the shortfall before suggesting more chargers or a larger connection.
This checklist supports self-review. No tutor marking or independent credential is included.
Related topics 5
Sources & evidence
All figures are original teaching inputs, not observations or published forecasts. The official source supplies industry context, not this dataset. Source link checked 17 October 2026. A live project needs charger efficiency curves, vehicle arrival and departure times, battery limits, site demand profiles and network approval.
AEMO network connections — process and requirements