Warmer Kiwi Homes Research and Evaluation

Warmer Kiwi Homes Impact Evaluation

Phase 2: Warmer Kiwis Study (2021-2022)

The Warmer Kiwis Study was led by Motu Economic & Public Policy Research. The study specifically focused on the heat pump component of the Warmer Kiwi Homes programme, and worked directly with a group of about 164 homeowners, who received grants for an efficient heater. Motu collected new data on health and wellbeing, the indoor environment in homes (including temperature and humidity), and electricity consumption to investigate the actual improvements achieved through EECA’s programme.

The Study also included a comprehensive cost benefit analysis utilising both ‘wellbeing and energy’ and ‘health and energy’ approaches. This provides a range of estimates for the benefit cost ratio of the programme, and follows Treasury’s Living Standards Framework.

Key conclusions:

• Households reported increases in warmth, comfort and satisfaction with their home, alongside a reduction in condensation and damp.
• Living area temperatures increased, with the greatest gains when it was coldest outside, and at breakfast and dinner/evening time.
• Household electricity use decreased at almost all times of day, and most significantly during the evening peak demand period.
• Overall electricity use decreased 16% over the winter months.
• Benefit cost ratios for the programme as a whole are 4.4 on a wellbeing and energy basis, and 1.9 on a health and energy basis.

Summary and final reports

Motu published both summary and full final reports in December 2022. The summary report contains key findings, while the full report contains further results, a description of the methodology, and a full list of all costs and benefits included in the CBA.

Evaluation of the Warmer Kiwis Homes Programme: Summary Report including Cost Benefit Analysis(external link)

Evaluation of the Warmer Kiwis Homes Programme: Full Report including Cost Benefit Analysis(external link)

View the webinar: Warmer Kiwis Study: cost-benefit analysis of heat pumps | Motu(external link)

Interim report

Motu published an interim report in January 2022. This is largely superseded by the final reports, but is included here for reference.

View the webinar: The Warmer Kiwis Study - An impact evaluation of the Warmer Kiwi Homes programme(external link)

To find out more visit Motu's website(external link)

Read the media release announcing 100 thousand retrofits and the publication of the evaluation(external link)

Phase 1: Review and scoping (2020)

In 2020, EECA commissioned Motu Economic & Public Policy Research and Allen & Clarke to review current evidence supporting the Warmer Kiwi Homes programme and estimate its current impact. This work also suggested areas for further study, which informed the scope of the subsequent Phase 2 Warmer Kiwis Study (described above).

Smart meter data analysis by Vector (2022)

Vector has modelled the impact of EECA’s retrofit programmes on household electricity consumption by combining smart meter data with data supplied by EECA on insulation and clean heater retrofits. The analysis draws on data from the Warmer Kiwi Homes and predecessor Warm Up New Zealand programmes and covers owner-occupied and rental properties. It is complimentary to the Warmer Kiwi Homes impact evaluation in that it spans a number of EECA programmes and hence target groups, but explicitly excludes any demographic information on households.

These results inform future demand projections, which Vector uses for network planning and management, and may be used to further analysis of emission reduction opportunities. For EECA, this analysis helps us to design high-impact retrofit programmes in the future.

To find out more visit the Vector website(external link)

Warm Up New Zealand cost benefit analysis (2012)

A comprehensive cost benefit analysis of the Warm Up New Zealand: Heat Smart programme was completed by Motu Economic & Public Policy Research, Covec, The University of Otago and Victoria University of Wellington in 2012. This report was the first of its kind worldwide to prove the significant health benefits of a large-scale insulation programme, and the favourable benefit-cost ratio resulting from this.

To find out more visit the Motu website(external link)