If you take 25%+ below as worse case scenario, you could pick say 15% for NZ. More for Electric
Running your car's air conditioning is the main contributor to reduced fuel economy in hot weather. Its effect depends on a number of factors, such as the outside temperature, humidity, and intensity of the sun. Under very hot conditions, AC use can reduce a conventional vehicle's fuel economy by more than 25%, particularly on short trips.1,2,3 The AC's effect on hybrids, plug-in hybrids, and electric vehicles (EVs) can be even larger on a percentage basis.2
https://www.fueleconomy.gov/feg/hotweather.shtml