Can I Reuse the Pipes and Panels from My Existing Gas Hydronic Heating System ?
Some users prefer the comfort and aesthetics of hydronic systems and the pipes and panels can also represent a significant prior investment that would ideally be re-used. When considering electrification a key question is whether the existing pipes and panels are suitable with a heat pump replacing the gas-powered boiler.
A key difference between hydronic and other heating solutions is that hydronic systems rely on convection air currents rather than fans to distribute the heat within the home. Hydronic heating systems utilize a network of pipes and panels to transfer hot water from a gas-powered boiler and water storage tank to warm the home and may include:
Panels to transfer heat into the air within the home.
Heated towel rails.
Pipes embedded in the floor slab.
Hydronic heating trenches.
A combination of the above.
If your gas boiler fails, it may be a good opportunity to electrify your heating solution. Whether you repair or replace your system having an upgrade plan ready-to-go is advisable to minimize delays.
Heat Pumps
Heat pump technology is a more efficient, environmentally friendly, and cost-effective heating solution than gas. Heat pump technology can be used with hydronic systems or split systems with one or multiple heads, or ceiling ducted or floor ducted systems. Notably, heat pump systems have proven effective even in cold climates, such as those in Scandinavian countries.
As with gas systems, heat pumps work less efficiently in drafty or poorly insulated homes. Therefore, it’s important to assess and improve the building envelope to ensure it meets a minimum sealing and insulation performance.
Zoning can significantly improve efficiency and reduce costs by allowing you to heat only the areas you use most. For example, you can heat living areas in the evening and preheat bedrooms before bedtime. If certain areas of your home are rarely used, such as entertainment rooms or spaces vacated by children who have moved out, zoning can prevent wasted energy. Some existing gas hydronic systems already include zoning capabilities, either through control systems or taps in the pipe network.
Split systems are a common heat pump solution, with multiple units deployed across different areas of the home. Key considerations include the sizing and placement of indoor and outdoor units. Indoor units are typically mounted high on walls, but floor-mounted or slimline units are also available.
A major advantage of split and ducted solutions is that they can provide both heating and cooling. Additionally, split systems can be deployed incrementally—starting with a single unit in a high-use area—allowing you to reduce gas reliance without fully upgrading your old hydronic system. This staged approach also makes split systems a good option if your current gas system fails unexpectedly.
For home extensions, you might choose to deploy new split or ducted systems in the new areas while maintaining or upgrading the hydronic system in existing spaces. Alternatively, you could expand the hydronic system to cover both old and new areas.
Finally, multiple split and ducted systems tend to be more energy-efficient than hydronic solutions due to heat losses in the pipe network.
Reusing Existing Hydronic Piping with a new Heat Pump
It is possible to replace an existing gas boiler and storage tank with a heat pump and reuse the existing hydronic pipe network, but there are important considerations:
Pipe Network Condition: Copper or plastic piping generally has a long lifecycle. However, if the system was not properly treated during installation or serviced regularly, a power flush may be needed to remove sludge and scale. This adds to the upgrade costs.
Water Temperature: Heat pump systems typically produce hot water at lower temperatures than gas boilers. This means the hydronic system may operate at lower temperatures, taking longer to heat a space. Some heat pumps can produce water at 75°C, which may suit systems designed for 85°C. However, older systems with smaller panels designed for high temperatures may require panel replacement.
Heat-Curve Technology: Heat pumps that operate on a heat-curve (using outdoor temperature sensors to adjust water temperature) are more efficient than cheaper, fixed-temperature units, which operate similarly to a gas boiler. Heat-curve units are particularly effective in reducing energy costs during mild weather.
Floor Heating: Heat pumps work efficiently with floor heating systems, which operate at lower water temperatures.
Pipe Insulation: Adding or upgrading insulation (lagging) on the pipe network may improve efficiency but can result in additional costs, especially if access to underfloor piping is limited.
As heat pumps typically supply water at a lower temperature than the existing gas powered system a good test for the viability of a heat-pump alternative may be to set the gas system thermostat to a lower temperature (say 60 degrees) and test how well the heating operates on cold days.
Theoretically a heat pump solution with hydronics could also provide a cooling solution however this is usually not practical due to temperature setting limitations to manage the effects of condensation.
Hydronic systems can be integrated with or separate from the main hot water system. However, combining a heat pump with a hydronic heating system and hot water supply can lead to higher costs. This is because the system must be sized to handle both heating and hot water demands during winter. In warmer months, when heating isn’t required, the larger compressor would just heat hot-water, increasing operational costs. In most cases, it’s more cost-effective to separate heating and hot water systems.
Ballpark Costs
Here are some approximate costs for heat pump Split System versus hydronic solutions:
Home Size Heat Pump Size Split Remediate Pipes Heat Pump Hydronic
Small (2 bed, 1 living) 10kW $3k Case-dependent $13k–20k
Medium (3 bed, 1–2 living) 15kW $6k Case-dependent $17k–25k
Large (multi-bed, multi-living) 22.4kW $10k Case-dependent $20k–35k+
Note: Estimated costs include available rebates. Hydroflush could be about $100 per panel or circuit if required
There may be a very significant cost to achieving all of the original design performance of the original gas hydronic system if it requires replacement of some panels and pipes, particularly if access is limited. However there may be some approaches that make a more economic design more viable. If you heat only parts of the home with hydronic at any particular time or use additional split systems to compliment the hydronic system then you may be able to deploy a more cost effective hydronic heat pump solution.
Summary
Choosing to reuse or deploy new hydronic pipes and panels depends on the specific characteristics of your home, including access, zoning, building envelope, budget and personal preferences. While hydronic systems offer comfort and aesthetics, split or ducted solutions may provide greater efficiency and flexibility for some homes.
If you are considering heat pump hydronic solutions, consulting an expert is essential to ensure the system meets your needs and maximizes efficiency.
Thanks to Tim from www.powrhouse.au and Steve from https://penplumbandhydronic.com.au/ for their input