Compare real-world kWh rates, system sizes, and energy-saving strategies
1. Quick kWh-Cost Table (SE Queensland Tariff 11 – $0.27/kWh*)
| System Size (Cooling kW)** | Avg. kWh / hr | Cost / hr | 8-hr Business Day | 250-Day Year |
|---|---|---|---|---|
| 7 kW Split | 2.1 kWh | $0.57 | $4.56 | $1,140 |
| 14 kW Ducted Split | 4.2 kWh | $1.13 | $9.04 | $2,260 |
| 25 kW Light-commercial | 7.5 kWh | $2.03 | $16.24 | $4,060 |
| 50 kW Rooftop Unit | 14.4 kWh | $3.89 | $31.12 | $7,780 |
| 85 kW Rooftop Unit | 23.5 kWh | $6.34 | $50.72 | $12,680 |
*Tariff 11 QLD April 2025 — adjust for your retailer.
**Cooling kW = nominal system capacity; kWh consumption assumes average COP of 3.3 at 32 °C ambient.
2. How to Calculate Your Air Conditioning Running Costs
Formula:
Running cost ($) = (Cooling kW ÷ COP) × Electricity rate ($/kWh) × Operating hours
Example – 25 kW system:
25 kW ÷ 3.3 COP = 7.6 kWh × $0.27 = $2.05/hour
3. Seven Proven Ways to Cut Your HVAC Energy Bills
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Raise set-point by 1 °C to save up to 10% on energy.
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Change filters quarterly — dirty filters add 5–15% load.
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Fit variable-speed drives (VSDs) to supply fans — average 20% reduction.
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Enable economiser cycle for free cooling below 22 °C.
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Use BTMS monitoring to detect compressor short-cycling early.
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Night purge offices to remove heat before startup.
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Replace R22 or fixed-speed systems over 15 years old — new inverter models can halve kWh use.
Related reading: Commercial Air Conditioning Maintenance Checklist
4. Case Study – Brisbane Office Cuts $3,200 Annually
Problem: 25 kW rooftop units running continuously at low efficiency.
Solution: Shelair installed VSD controls and optimised airflow balance.
Result: 17% energy reduction = $3,200 saved per year. ROI ≈ 15 months.
5. Frequently Asked Questions
What’s the cheapest tariff for commercial HVAC?
Larger sites on Tariff 20 or demand-based tariffs can pay 10–15% less per kWh.
Does solar offset HVAC power costs?
Yes — most systems operate during daylight. A 30 kW solar array can offset 40% of annual HVAC consumption.
Should I leave AC on overnight?
Not usually. Overnight heat gain outweighs any stored cooling. Use night purge or temperature setback only.
6. Free Commercial Cooling Audit and kWh Calculator
Want to know your exact running costs and payback?
Book a free commercial cooling audit with Shelair — includes a 5-year workmanship guarantee on any approved upgrades.
Servicing Brisbane, Gold Coast and Sunshine Coast
Phone: 07 3204 9511
Email: info@shelair.com.au
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