Hot Water systems (HWS)

Hot water is typically one of the largest energy demands of a home, and is a key part of the NatHERS WoH scheme.

There are a variety of different selectable hot-water systems and efficiency levels that you can select for your project as outlined below.

1 - Hot Water Zone

The Hot Water zone is of importance when selecting Solar Hot Water or Heat Pumps systems as it allows the STCs (Small Technology Certificates) to be accurately determined for your project's post-code.

There are 4 Hot Water climate zones designated for Solar Hot Water systems, and 5 Hot Water climates zones designated for Heat Pump systems (Climate Zone 5 post-codes are Climate Zone 4 for Solar Hot Water systems). Hero determines the correct Hot Water zone via the Project's post-code as per the Clean Energy Regulator (CER) post code to climate zone report, see: https://www.cleanenergyregulator.gov.au/DocumentAssets/Pages/Postcode-zones-for-solar-water-heaters-and-heat-pumps.aspx

Image Source: 1stchoicehotwater.com.au

2 - Hot Water Demand

The Hot Water demand on a Litres per Day per Occupant basis is shown in the information header of the Hot Water section to provide additional information for users. This is currently not editable in Hero.

3 - Regulated Load

Hot Water is one of the Regulated Loads that contribute to the NatHERS Whole of Home rating.

4 - Hot Water Type

There are a wide range of Hot Water types available in Hero and NatHERS WoH that cover the vast majority of possible hot-water systems used in Australian homes. These are detailed below. 

• Electric Storage (Peak): An electric element hot water-heater with a storage tank, that operates on a peak daytime usage profile and should be used for small hot water systems or systems configured to heat during daytime hours (such as is common so as to match solar PV production). Efficiency cannot currently be varied in NatHERS WoH.
• Electric Storage (Off-Peak): An electric element hot  water-heater with a storage tank, that operates on an off-peak (i.e. night time to early morning) tariff or controller and should be selected for large hot water systems where such an operation is expected. Efficiency cannot currently be varied in NatHERS WoH.
• Electric Instantaneous: An electric element hot  water-heater that operates instantaneously (i.e. on demand or continuously). Many instantaneous electric hot-water systems require 3-phase electricity connections to be able to raise the incoming water temperature to a sufficient degree required for normal domestic water flows, however do not suffer from storage losses. Efficiency cannot currently be varied in NatHERS WoH.
• Gas Storage: A gas element hot water-heater with a storage tank, that operates when required to maintain the appropriate water temperature. Efficiency is determined via the Star Rating of the system.
• Gas Instantaneous: A gas element hot water-heater that operate instantaneously (i.e. on demand or contiously). Gas instantaneous heaters have a small background pilot energy demand. Efficiency is determined via the Star Rating of the system.
• Heat Pump (Peak): An air-to-water heat-pump hot water heater with a storage tank, that operates on a peak daytime usage profile and should be used for small hot water systems or those configured to heat during daytime hours (such as is common so as to match solar PV production). Efficiency is determined via the selected STCs of the system.
• Heat Pump (Off-Peak): An air-to-water heat-pump hot water heater with a storage tank, that operates on an off-peak (i.e. night time to early morning) tariff or controller and should be selected for large hot water systems where such an operation is expected. Efficiency is determined via the selected STCs of the system.
• Solar Electric Boost (Peak): A solar thermal (i.e. thermosiphon, evacuated tube or flat-plate panel) hot water heater with a storage tank that is supplemented by an electric element boost heater, that operates on a peak daytime usage profile and should be used for small hot water systems or those configured to heat during daytime hours (such as is common so as to match solar PV production). Efficiency is determined via the selected STCs of the system.
• Solar Electric Boost (Off-Peak): A solar thermal (i.e. thermosiphon, evacuated tube or flat-plate panel) hot water heater with a storage tank that is supplemented by an electric element boost heater, that operates on an off-peak (i.e. night time to early morning) tariff or controller and should be selected for large hot water systems where such an operation is expected. Efficiency is determined via the selected STCs of the system.
• Solar Gas Boost: A solar thermal (i.e. thermosiphon, evacuated tube or flat-plate panel) hot water heater with a storage tank that is supplemented by a gas element instantaneous boost heater, that operates on demand as required. Efficiency is determined via the selected STCs of the system.
• Wood: A solid wood fuelled water heater. No benefit is currently attributed to water-jackets / heat-exchanges fitted to wood heating devices in NatHERS WoH. Efficiency cannot currently be varied in NatHERS WoH.

5 - Hot Water Efficiency (STCs / Star-Rating)

Depending on the selection of Hot Water type, there may appear an efficiency row below the Hot Water type. This will only show for those systems where the efficiency can be varied (i.e. Gas, Heat Pump and Solar Hot Water types).

5.1 Gas Star Ratings

For Gas Storage and Gas Instantaneous Hot Water systems you will be show a Star Rating row that allows you to select the efficiency of the gas hot water service being specified.

While GEMS mandate minimum performance requirement for Gas Hot Water heaters, you won't find the Star-Rating on the energyrating.gov.au website, however you can find a range of Gas Hot Water systems and their Star-Ratings via the registry hosted by Australia Gas Association (AGA) at https://www.aga.asn.au/product_directory/  in PDF form, such as shown in the excerpts below:

Hero will limit the selection of Star Rating within the available range of products (4 to 5 stars for gas storage and 4 to 7 stars for gas instantaneous).

5.1 Solar Hot Water & Heat Pump STCS

The efficiency of Heat Pumps and Solar Hot Water systems are assessed in NatHERS WoH via their equivalent STC (small technology certificates).

The required STC value for NatHERS WoH is the 10-year deeming period STC and not the remaining deeming period towards 2030 which is what will be reported by the REC Registry Calculator at https://www.rec-registry.gov.au/rec-registry/app/calculators/swh-stc-calculator.

To match the correct STCs for your product, you should use the REC Registry Register of Solar Water Heaters at: https://www.cleanenergyregulator.gov.au/RET/Scheme-participants-and-industry/Agents-and-installers/Small-scale-systems-eligible-for-certificates/Register-of-solar-water-heaters

These spreadsheets show the correct 10-year deeming period STCs which are valid NatHERS WoH across the various climate zones as shown in the example extract below:

When you have determined the correct 10-year deeming period STC for your system you can select it in Hero as per the below:

Hero will limit the selection of STCs to those available in your climate zone (under a 10-year deeming period). If there are no systems in that climate zone that have that STC value then Hero will show an error, this likely suggests you are using the wrong STC value (such as not using the 10-year deeming period value)

6 - Hot Water Results

As per all Appliance categories, the individual results of the Hot Water systems are shown in each section along with the percentage impact of Hot Water to the overall Operational Energy, Running-Cost and Operational Emissions of the Project. You can hide this Category Result in the Settings section of the Appliance View.

7 - Hot Water Comments

As per all Appliance categories, you can add your own comments, description, recommendations or explanations to the Hot Water section to include in your report exports. You can hide this Comments section in the Settings section of the Appliance View.