A New Zealand Heat Pump Retrofit Programme: Warmer, Drier, Happier, Cheaper

We evaluate temperature, humidity, electricity use and subjective wellbeing impacts of installing heat pumps through New Zealand's Warmer Kiwi Homes programme. The government-funded programme included provision of heat pumps in already insulated houses that lack efficient heating. Staggered installation enables difference-in-difference estimates of impacts of heat pump installation on living area temperatures and relative humidity, and on household electricity use. Surveys conducted before and after installation provide demographic and housing information plus measures of occupants' wellbeing. Living areas of treated houses experience increases in temperature which are most pronounced around breakfast and evening times, and when outdoor temperatures are low. Houses also experience reductions in relative humidity. Winter electricity use falls in houses that have a heat pump fitted, with electricity savings peaking in the evening. Heat pump installation reduces perceptions of living in a cold house and improves aspects of residents' mental wellbeing during winter.