Sustainability options for retrofitting New Zealand houses: Theoretical cost benefit analysis

Michael Phillips.

A theoretical cost benefit for options to retrofit for water and energy was carried out using ALF. At a national level, the following options have a theoretical internal rate of return greater than 5% making them worthwhile implementing from a financial perspective:

  • Rainwater tanks (2,000 litre) for Auckland only (assuming 100% water retention)
  • Low flow shower heads for high pressure systems
  • Water efficient (“AAA”) washing machines
  • Water heating upgrade (if current water heating tank needs replacing) to either solar hot water heating or heat pump hot water heating or instant gas hot water heating
  • Floor insulation
  • Ceiling insulation