Understanding Standards: AS/NZS 5125.1

AS/NZS 5125.1:2014 outlines the method for determining the performance characteristics of air-source heat pump water heaters. It plays a critical role in the evaluation and compliance of heat pumps under Australia and New Zealand’s energy efficiency frameworks.

The results of AS/NZS 5125.1 testing feed directly into modelling conducted in accordance with AS/NZS 4234.

Performance testing approach

AS/NZS 5125.1 sets out standardised testing procedures and covers both stand-alone systems, where the heat pump is separate from the tank, and integral units, where the condenser wraps around the tank. The standard applies to systems under 700 L in size.

The main outputs from the test are thermal capacity, power input, and coefficient of performance (COP). Thermal capacity shows how much heat is delivered to the tank, power input shows how much power is used by the compressor and auxiliaries, and COP is the ratio of useful heat output to electrical input.

Full heat-up cycles are performed at different ambient air and water temperatures in environmentally controlled chambers. A low-temperature performance test is also performed to characterise system performance where frost build-up on the evaporator is likely.

Link between AS/NZS 5125.1 and AS/NZS 4234

The results from AS/NZS 5125.1 testing are used to train a regression model that estimates the unit’s COP and input power consumption. This feeds directly into the transient simulation models required by AS/NZS 4234.

The low-temperature performance test contributes to adjustments in efficiency within the model to account for frosting effects in cold conditions. Without AS/NZS 5125.1 testing, products under 700 L in size could not be modelled under the AS/NZS 4234 framework.

Design and compliance implications

Understanding AS/NZS 5125.1 is an important part of designing heat pump water heaters for the Australian market.

Systems that perform poorly under these test conditions may receive low annual efficiency ratings, fail to meet minimum hot water delivery temperatures, or qualify for reduced federal and state incentives. Low-temperature testing and test points relevant to rebate calculations are especially important.

Manufacturers should consider compressor and evaporator sizing, control logic, set points, dead-bands, and tank aspect ratio when optimising for favourable AS/NZS 5125.1 results.

How EnergyAE can help

EnergyAE supports manufacturers and suppliers by connecting them with laboratories that carry out AS/NZS 5125.1 testing. We can also help prepare models for testing, interpret results, complete AS/NZS 4234 modelling using 5125.1 test data, and support the full pathway from testing through to scheme registration.