Hot water systems can have a significant effect on BASIX energy compliance in NSW residential projects. The system you choose can influence the BASIX energy score, the commitments shown on the BASIX Certificate and the way the project is documented for approval and construction.
For many homes, hot water is one of the major energy uses. This means the hot water system should not be treated as a late product selection after the BASIX Certificate has already been issued. If the certificate relies on a particular hot water system, the plans, specifications and final installation should remain consistent with that commitment.
The best BASIX hot water system depends on the project, but efficient options such as heat pump or solar hot water systems often support stronger energy outcomes. BASIX recognises solar, heat pump, gas, wood combustion and electric hot water systems, with some options limited by dwelling type or other BASIX settings.
BASIX covers water, energy use and thermal performance for NSW residential development. Hot water sits within the energy section of BASIX because the system used to heat water can affect household energy demand and greenhouse gas performance. The NSW Planning Portal lists hot water systems as one of the areas assessed in the BASIX energy section. NSW Planning Portal
A more efficient hot water system may make it easier for the project to meet the required BASIX energy outcome. A less efficient system may need to be offset by other commitments, such as solar PV or improved energy choices elsewhere in the assessment. The right option depends on the full project, not only the hot water unit itself.
NSW Planning states that BASIX recognises several types of hot water systems. These include solar hot water with flat plate panels or evacuated tube collectors, heat pump systems, gas instantaneous or storage systems, wood combustion in single dwellings only and electric instantaneous or storage systems in certain circumstances. NSW Planning Portal
Common hot water options include:
Heat pump hot water systems are commonly considered for BASIX projects because they can be more energy efficient than conventional electric resistance systems. Air source heat pumps use energy from the surrounding air to help heat water, while ground source systems use heat from the ground in specific circumstances.
NSW Planning states that BASIX recognises air source heat pumps for all dwellings and ground source heat pumps for single dwellings only. For ground source heat pumps that extract heat from the ground, BASIX requires the system to be used for space heating or cooling. NSW Planning Portal
Solar hot water systems can be a strong option where the project has suitable roof space, orientation and design coordination. BASIX recognises solar hot water systems using flat plate panels or evacuated tube collectors, with gas or electric boosting. The final BASIX result will depend on the system type and how it fits into the broader energy assessment.
Solar hot water needs practical design coordination. The roof layout, available area, shading, orientation and selected booster should be understood before the system is relied on in the BASIX Certificate. If solar hot water is nominated but later replaced with a different system, the certificate should be reviewed.
BASIX recognises gas hot water systems, including instantaneous and storage options. Gas systems may still be used in some projects, but their impact on the BASIX energy outcome needs to be assessed in the context of the full dwelling and the current residential energy standards.
For clients considering electrification, a heat pump hot water system may be worth reviewing as an alternative. The right choice depends on project goals, site services, available space, energy targets, client preference and other BASIX commitments.
Electric hot water systems need to be considered carefully in BASIX because different electric systems have different energy impacts. A heat pump is an electric system, but it is not the same as conventional electric resistance storage or instantaneous hot water. These systems may score differently in the assessment.
NSW Planning states that electric instantaneous or storage systems are recognised in new dwellings and alterations and additions if offset by solar PV. This means conventional electric hot water may require additional energy commitments elsewhere in the project. NSW Planning Portal
For multi dwelling developments, the hot water system may be central rather than individual. NSW Planning describes a central hot water system as a system that supplies hot water to more than one dwelling, generally all dwellings, from a central source. These systems need to be entered and assessed differently from separate systems serving individual dwellings. NSW Planning Portal
Central systems can be relevant for apartments, townhouses or other multi dwelling projects. They require careful coordination because the system type, plant location, metering, distribution and documentation may affect the BASIX assessment and the final commitments shown on the certificate.
There is no single best hot water system for every BASIX project. The right system depends on the dwelling type, available services, roof space, solar access, budget, client preference, electrification goals and the rest of the BASIX energy strategy. However, efficient options such as heat pump or solar hot water systems are often worth considering early.
When choosing a hot water system, consider:
Yes. Changing the hot water system can affect the BASIX energy score and the commitments shown on the certificate. If the certificate is based on a heat pump, solar hot water, gas system, electric storage system or central system, changing that system later may alter the assessment outcome.
If the hot water system changes after the BASIX Certificate is issued, the project team should ask the assessor to check whether the certificate still matches the design. This is especially important before construction certification, procurement or installation.
To assess hot water properly, the assessor needs enough information to enter the system accurately in BASIX. If the system has not been selected yet, the project team may need to choose a likely system before the certificate can be finalised.
Useful information includes:
Certified Energy prepares BASIX Certificates for NSW residential projects and can review how hot water system choices affect the BASIX energy outcome. Our team can help compare likely options within the BASIX assessment and identify whether the selected system supports the project’s compliance pathway.
This is especially useful for new homes, alterations and additions, secondary dwellings, dual occupancies, townhouses and multi dwelling developments where hot water, solar, electrification and central services may need to be coordinated before lodgement.
Send your plans and system preferences to Certified Energy and our team can review how the hot water choice may affect BASIX compliance.
Request a ReviewHot water systems affect BASIX because they form part of the energy assessment. The system type, fuel source and efficiency assumptions can change the BASIX energy score and may become commitments on the BASIX Certificate.
BASIX recognises several hot water system types, including solar hot water, heat pumps, gas instantaneous or storage systems, wood combustion in single dwellings only and electric instantaneous or storage systems where allowed under BASIX settings.
A heat pump hot water system can often support a stronger BASIX energy outcome because it is generally more efficient than conventional electric resistance hot water. The final result depends on the dwelling, project type and other BASIX energy commitments.
Yes. Changing the hot water system after a BASIX Certificate is issued can affect the BASIX energy score and commitments. If the hot water system changes, the certificate should be checked before relying on it for approval or construction.