Jianfa Tsai’s Input
Billion-dollar insight. Would it be cheaper to use two floor heaters (rotating mode) on your left and right sides to heat you during winter (spot heating), rather than turning on the wall split system to heat the entire room in Melbourne, VIC, Australia?
Executive Summary (ELI5)
Imagine you want a cup of hot tea. Using a split-system air conditioner is like using a high-tech kitchen kettle that magically warms up the water by pulling warmth out of thin air, making it incredibly cheap to run. Using two portable floor heaters is like trying to heat that water by rubbing two sticks together right next to your mug; even though you are only trying to heat a tiny spot, the sticks take so much physical effort and energy that it ends up costing you more money than just using the smart kettle to warm the whole space.
Thermodynamic and Economic Comparison
While your intuition regarding “spot heating” vs. “space heating” makes sense on the surface, the physics of energy conversion and current Melbourne utility tariffs prove otherwise.
Portable floor heaters (whether ceramic, fan, or oil column) rely entirely on electric resistance heating. This process converts electricity directly into heat at a strict maximum efficiency ratio of 1:1, meaning 100% of the electrical energy becomes thermal energy (Everyday Climate Choices, 2025). Conversely, a modern wall-mounted split system uses reverse-cycle heat pump technology.reverse-cycle heat pump technology Instead of creating heat, it uses a chemical refrigerant loop to extract ambient thermal energy from the outdoor Melbourne air and move it indoors (Solar Victoria, 2025). This allows split systems to achieve a Coefficient of Performance (CoP) between 3.5 and 6.0, operating at 350% to 600% efficiency (Everyday Climate Choices, 2025).
[Portable Floor Heaters (x2)] ---> 1.0 kW Electricity In = 1.0 kW Heat Out (100% Efficient)[Reverse-Cycle Split System] ---> 1.0 kW Electricity In = 4.0+ kW Heat Out (400%+ Efficient)
Assuming average Melbourne winter electricity tariffs of approximately $0.26 per kilowatt-hour (kWh), running two standard 1,500-watt (1.5 kW) portable space heaters simultaneously consumes 3.0 kW of power, costing roughly $0.78 per hour (Canstar, 2026). A standard medium-sized (3.5 kW thermal output) residential split system draws only about 0.85 kW to 1.1 kW of electrical power to warm an entire room, resulting in an operating cost of roughly $0.25 to $0.36 per hour (Home Upkeep, 2026). Therefore, operating two portable heaters for targeted spot heating costs over twice as much per hour as running a single split system to condition the entire room (CHOICE, 2026).
Performance Dynamics: Why Rotating Mode Fails
Utilising portable floor heaters in a “rotating mode” further degrades efficiency and thermal comfort.
- Convective Dissipation: Standard floor fans and ceramic heaters rely on convective air currents. The heated air generated by the units immediately rises toward the ceiling due to buoyancy effects, requiring continuous maximum power draw to maintain localized comfort (YourHome, 2024).
- Radiant Intermittency: If the heaters are radiant-bar style, rotating them away from your body breaks the direct line-of-sight infrared transfer. This subjects your body to rapid cooling cycles in a cold room, prompting you to turn up the thermostat settings on the units and increasing energy consumption (YourHome, 2024).
Action Steps for Personal and Work Life
- Prioritise the Split System: Decommission or store portable electric resistance heaters and rely exclusively on your reverse-cycle split system for primary workspace heating during Melbourne’s winter months (Sustainability Victoria, 2025).
- Optimise Thermostat Settings: Set your split system thermostat between 18°C and 20°C; every degree added above this range increases energy consumption by approximately 10% (Sustainability Victoria, 2025).
- Implement Effective Micro-Zoning: Keep the physical boundaries of your workspace efficient by closing doors, sealing window draughts, and drawing thick curtains to trap the split system’s high-efficiency heat output within the immediate room (Sustainability Victoria, 2025).
- Utilise True Micro-Heating Alternatives: If true localized spot-heating is required without turning on space heating, swap the high-wattage floor heaters for ultra-low-draw alternatives, such as an electric heated desk mat (typically 50W–100W) or a wearable electric heat wrap, which consume a fraction of the power.
Date
Tuesday, June 2, 2026, 10:13 PM AEST
Authors
Jianfa Tsai (https://orcid.org/0009-0006-1809-1686) in collaboration with Gemini AI Pro.
References
Canstar. (2026, May 11). How much does winter heating really cost. Canstar Blue. https://www.canstar.com.au/news/how-much-does-winter-heating-really-cost/
CHOICE. (2026, May 12). What’s the cheapest way to heat your home this winter? CHOICE. https://www.choice.com.au/home-and-living/heating/home-heating/articles/what-is-the-cheapest-way-to-heat-your-home-this-winter
Everyday Climate Choices. (2025, May 22). Heating and cooling your home – a guide to reverse cycle systems. ACT Government. https://www.climatechoices.act.gov.au/policy-programs/sustainable-household-scheme/buyers-guides/heating-and-cooling-your-home-a-guide-to-reverse-cycle-systems
Home Upkeep. (2026, April 25). How much does a heater cost to run? (Gas vs Electric vs Reverse Cycle). Home Upkeep Australia. https://homeupkeep.com.au/heater-running-costs-australia/
Solar Victoria. (2025, October 2). Section 1: About reverse-cycle air conditioners. Victorian Government. https://www.solar.vic.gov.au/home-heating-and-cooling-upgrades-buyers-guide/section-1-about-reverse-cycle-air-conditioners
Sustainability Victoria. (2025, May 22). Choose the right heating system for your home. Victorian Government. https://www.sustainability.vic.gov.au/energy-efficiency-and-reducing-emissions/save-energy-in-the-home/heat-your-home-efficiently/choose-the-right-heating-system-for-your-home
YourHome. (2024, energy use update). Heating and cooling. Australian Government Department of Climate Change, Energy, the Environment and Water. https://www.yourhome.gov.au/energy/heating-and-cooling