How much energy does a Passive House use?

It is difficult to directly compare energy consumption in a Passive House with a standard NZ building code (NZBC) house due to the way we occupy our homes. By this I mean the way in which we heat our homes.

The World Health Organisation (WHO) recommends a minimum indoor temperature of 20 degrees. An indoor temperature below 16 degrees increases the risk of respiratory illnesses, and below 12 degrees increase the stress on the cardiovascular system which can lead to strokes and heart attacks. In NZ the majority of people will have a heat pump in the living room that set to 24 degrees, while the other rooms might be 12 degrees or colder in winter. In order to maintain an indoor temperature of 20 - 22 degrees we need to look at heating every room in the home.

Heating the whole house for a 120m2 NZBC house in wellington would on average use around 6,120kWh per year to maintain an indoor air temperature of 20 degrees. A Passive House on the other hand must be designed to use less than 15 kWh/m2 per year which equates to less than 1,800kWh per year. In this scenario a Passive House would use greater than 70% less energy than a NZBC house in Wellington. If we assumed an average price of 25c per kWh, the passive house would save around $1,080 per year on heating.

If we change the location of Queenstown, a Passive House will be 85% more energy efficient than NZBC house which would require around 11,760kWh per year. With a savings closer to $2,490 compared with whole home heating of a NZBC house.

Passive House is about energy efficiency, this is like comparing the efficiency of a 2022 Ford Ranger that has a fuel consumption of 7.2l/100km with a 2023 Audo e-tron Gt which averages 21kW/100km. At $2.70/l the Ford Ranger would cost you $19.44/100km. While at $0.30 a kWh, the Audi e-tron would cost you $7.35/100km. I know which car I would rather have.