Heat Pump Technology
The energy-efficient future of hydronic heating
Converting from Gas Boiler to Heat Pump
Why make the switch?
I generally wouldn't recommend simply removing a working condensing gas boiler unless it's ready for replacement. However, when the time comes, heat pumps are an exceptional option for hydronic heating, especially for in-slab systems.
Efficiency: Heat pumps are extremely energy efficient. 1 kWh of input produces around 4.6 kWh of heat output (COP of 4.6).
Compare this to a high-efficiency gas boiler, where 1 kWh of input produces only about 0.9 kWh of output. Coupling a heat pump with solar PV panels can reduce your running costs even further.
Types of Heat Pumps
- Air-to-Water: The standard for hydronic heating systems.
- Air-to-Air: Commonly known as reverse-cycle air conditioning.
- Ground Source (Geothermal): Highly efficient but often economically unviable in Australia due to installation costs.
Factors Affecting Output
Heat pump performance varies based on:
- Ambient air temperature
- Water inlet temperature
- Water outlet temperature
Understanding Capacity
Heat pump sizing for hydronic heating in Australia is typically rated based on these standard conditions:
Outside air temperature:
7°C
Water inlet temperature:
30°C
Water outlet temperature:
35°C
Output capacity reduces with lower air temperatures or higher required water outlet temperatures.
Energy Cost Comparison
Based on typical Canberra, Australia prices
Heat Pump
$0.62
per 10kWh
- 450% Efficiency
- Electricity @ $0.28/kWh
- Solar PV compatible
Older Gas Boiler
$1.93
per 10kWh
- 70% Efficiency
- Natural Gas @ $0.135/kWh
- Fossil fuel based
Heat Pump Sizing Guide
Determine your cost savings and estimated heat pump size
1. Gas Consumption
$
MJ
$
MJ
$
MJ
$
kWh
2. Heat Pump Savings Calculation
$
$
$
Total Estimated Savings
Switching could save you approximately:
$
% ReductionRecommended Heat Pump Size
Quick Sizing Guide
In-Slab Heating
Well-insulated & zoned: ~70W/m²
(e.g., 200m² home = 14kW unit)
Average insulation: ~100W/m²
(e.g., 200m² home = 20kW unit)
Radiators
Well-insulated & oversized radiators: ~100W/m²
(e.g., 200m² home = 20kW unit)
Average home: ~120-150W/m²
(e.g., 200m² home = 24-30kW unit)
Ideal Heat Pump Positioning
Location matters for efficiency and longevity.
- Northern Aspect: Place on the north side (southern hemisphere) to gain winter sun for better performance.
- Noise Control: Install away from bedroom windows.
- Airflow: Ensure plenty of clearance around the unit, especially the front fan.
- Access: Allow space for servicing and maintenance.
- Snow Areas: Mount off the ground and consider a top cover (while maintaining airflow).
Zoning & Monitoring
Zoning improves efficiency significantly. Unlike gas boilers which have fixed capacities, heat pumps benefit greatly from tailored load management. Learn more about Zoning.
