Requirements for Unvented Electric Storage Water Heaters - Minimum Energy Performance Standards

Since 1 October 1999, electric storage water heaters manufactured in or imported into Australia must comply with Minimum Energy Performance Standard requirements which are set out in AS 1056 Part 1.

Product Definition: Electric storage water heaters of the unvented type (displacement) without an attached feed tank. Heat exchanger models and low pressure (vented) models are not included at the present time.

Test Standards: Note that the standard for electric water heaters is published only by Standards Australia. New Zealand have a separate standard for storage water heaters (NZS 4606.1) which specifies different allowable heat losses which are not relevant for Australia.

AS1056: Storage Water Heaters Part 1: General Requirements The Minimum Energy Performance Standards requirements are set out as maximum allowable standing heat loss values in Amendment 3 dated 5 August 1996 (column 2).

Part 1 of the standard defines the test procedures for the determination of standing heat loss and also sets out the maximum allowable heat loss values under Minimum Energy Performance Standards in Australia.

This standard can be purchased from SAI Global under licence from Standards Australia.

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Overview of the Test Procedure for Electric Storage Water Heaters

The standing heat loss is measured at a nominal 20°C ambient air temperature and a water storage temperature of 75°C (for most tanks), giving a ambient air/hot water temperature difference of 55K. The test measures the energy consumed over a number of complete thermostat cycles, and this is normalised to a heat loss per 24 hour period. The test procedure is set out in Appendix B of AS1056.1-1991. No hot water is drawn off during the test (ie it is a static standing heat loss test).

Water heater capacity under AS1056.1 is defined as one of the pre-defined hot water delivery capacities, rather than the volume of the tank. Hot water delivery capacity is defined as the volume of hot water that can be delivered before a 12°C temperature drop occurs (after the tank reaches its thermostat temperature and the power is disconnected). Hence a tank that has good stratification will obtain a hot water delivery capacity which is close to the total tank volume. The flow rate of hot water under the test depends on the tank capacity:

9-10 litres per minute for <= 125 litre capacity
12-13 litres per minute for 160 to 400 litre capacity
15-17 litres per minute for >= 500 litre capacity

The test procedure for the determination of hot water delivery capacity is set out in Appendix C of AS1056.1-1991.

The test method is under revision and a joint AS/NZS standard is expected in 2003.

Note that International Electrotechnical Commission IEC60379 for water heaters uses a temperature difference of 45K, so European heat loss values will appear to be lower than those measured in Australia. Minimum energy efficiency values set out by the US Department of Energy are defined as "Energy Factors", which are a task based test with a set 6 drawoffs of 40.6 litres each (total 243.4 litres) per day with a temperature difference of 37.5K, so these values are not directly comparable to standing heat loss tests in Australia.

Actual in use energy consumption can be determined using the standing heat loss value obtained under AS1056.1 and using the methods set out in AS1056 Storage water heaters - Part 4: Daily energy consumption calculations for electric types (1997). A more versatile model for hot water in-use energy consumption for a wide range of water heater types and climates is contained in AS4234 Solar water heaters - Domestic and heat pump - Calculation of energy consumption (1994).

These standards can be purchased from SAI Global under licence from Standards Australia.

This page last modified 09 May 2007