The energy demand is a complex issue for householders in New Zealand, since a large number of dwellings were built before energy efficiency regulation came into force in 1979. To heat the average New Zealand home takes a lot of energy, and therefore many householders choose to limit their heating space.   Powerco, New Zealand’s second-largest distribution company is conducting a two-year study, called Powering tomorrow’s homes. The project aims to uncover opportunities to shift peak loads on Powerco’s electricity network, by using a range of networks surveys. The dwellings that have been chosen to contribute to this study have gone through a large retrofit in 2014.   This study has been limited to verifying the effectiveness of three different heating systems, within three houses in New Zealand. It has been based on global data such as climate, temperature, humidity, design of the house and the family’s different behavioural patterns.   Three case models have been established in the program IDA ICE, to simulate and calculate the amount of used and delivered energy for space heating. Thereafter four main energy simulations were conducted to study the heating system before the intervention, after the intervention and a trial to see which heating system that is best suitable for each house. The new settings together with the original heating systems were also calculated. The simulations are also limited to summer respective winter because the heating systems are used differently depending on season. Data of location and climate files have been limited to Auckland and Wellington.   The results show that the most energy efficient heating system for dwelling A is the heat pump and infrared panel it uses today and for dwelling C its dwelling A’s heating system. Data demonstrate that the most effective heating system for dwelling B varies depending on climate, showing that dwelling C’s gas heating is more efficient for a warmer humid climate in Auckland and that dwelling A’s heat pump is better for a colder climate in Wellington. Comparison between the new settings and the old heating system (two radiators) shows that dwelling A’s new heating system (infrared panel & a heat pump), requires less delivered energy than the old heating system. Dwellings B’s new heating system (gas fire, an infrared panel & a radiator) is the most effective in Auckland however the old heating system (an air source heat pump, oiled-filled radiators & a gas wall heater) is the most energy efficient in Wellington. Dwelling C’s new heating system (gas central heating & a gas fire) has a lower delivered energy than the old heating system (gas fire, two heat pumps, radiators and heating panels) for summer in Auckland, while it has a higher delivered energy for winter in both Wellington and Auckland, and also summer in Wellington.       In conclusion, the new heating systems deliver warmer, more comfortable dwellings for less delivered energy than the previous. This presents an opportunity for Powerco to use newer gas heating to curb electricity load, and also shows the opportunity to use heat pumps to reduce peak demand through increased energy efficiency.