Life cycle assessment of domestic hot water systems in Australia

Highlights

The performance of each hot water system was modelled based on installation in Australian climate zone 3 and the standard AS/NZS 4234:2011.

An electric storage hot water system was found to have the largest carbon footprint and energy use over its life cycle.

A consumer could reduce their carbon footprint but replacing an electric hot water system with either a gas or solar electric system.

The energy consumed by the hot water systems in heating water accounted for 87% to 99% of the carbon footprint of all systems.

The carbon footprint and embodied energy payback periods of the solar hot water systems were found to be less than 12 months.

Abstract

Global warming potential (GWP) and primary energy demand (PED) were investigated for a range of domestic hot water systems in Australia, from cradle-to-grave, using streamlined life cycle assessment. The production of the hot water systems was modelled using inventory data calculated using specifications from a range of Australian manufacturers. The use stage of the life cycle was modelled assuming installation within Australian climate zone 3 according to the Australian and New Zealand water heater standard (AS/NZS 4234:2011). The electric storage hot water system had the highest GWP and PED, followed by solar electric, gas storage, gas instantaneous, and then solar gas instantaneous system. The solar hot water systems were shown to significantly reduce the GWP and PED compared to their non-solar counterparts, despite the additional impacts associated with production. The use stage accounted for 87%–99% of the GWP or PED of all systems. GWP and PED payback periods were less than 12 months for the solar hot water systems.

Keywords

  • Life cycle assessment;
  • Domestic hot water system;
  • Solar hot water system;
  • Carbon footprint;
  • Embodied energy

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