For Shay and Jo to achieve Zero Energy for their project required generating as much energy onsite via renewable sources as was used in the home. Zero Energy is measured over a calendar year and in 2013 – the first year after Shay and Jo’s house was completed – the house-wide monitoring system recorded all energy generated and used.
The results for this first year were:
In the first year, the Zero Energy House generated more than double the energy used.
In that first year, the Zero Energy House generated more than double the energy used. This substantial difference is, in part, because the house was designed and built to be Zero Energy even after Shay and Jo had a family. For most of 2013 it was just the two of them living in the home, so energy use was lower than it is now, when they share the house with their two children.
The couple estimated that, once the house was full, energy use would increase by 40% to around 3,200 kWh, which is still less than what the photovoltaic system (PV) generates. This surplus capacity was intentionally planned, as Shay and Jo wanted extra renewable energy available in the future to allow them to charge an electric car – which they began doing in 2018.
<p>Minimising energy use is a key goal in planning for Zero Energy as it reduces the amount of energy that needs to be generated, which in the case of the Zero Energy House meant a smaller PV array. Shay and Jo’s consumption of 2,361 kWh in 2013 was around 25% of the energy used in a typical Auckland home<sup>1</sup>. Reducing energy use by nearly 75% was achieved by focusing on three key areas:</p>
<p>The chart below compares the energy profile of the Zero Energy House (ZEH) (using data from September to December of 2013<sup>2</sup>) against that of a typical Auckland home (using data from the BRANZ Household Energy-use Project (HEEP)<sup>3</sup>.</p>
The 5,387 kWh generated by the PV panels roughly matches the performance modelled during design.
The 5,387 kWh generated by the PV panels in 2013 roughly matches the performance Shay and Jo had modelled during the design stage, with some variation month to month.
The chart below shows monthly patterns of energy generation and use compared with what was predicted during design. The four data series are:
The shaded brown area indicates the total amount of energy used over the year. The shaded green area indicates the surplus energy generated from the solar PV system that is not required for use in the home and can be exported to the grid.
Achieving Zero Energy allowed Shay and Jo to reduce reliance on energy sources that generate carbon dioxide and to reduce the costs of running their home. In fact, over the first year they ended up making a profit on energy. And, with the amazing results of their first year of occupation, their house was certified as Net Zero Energy by the Living Future Institute. One of the most important lessons from their energy results, though, is that Shay and Jo’s energy model helped them plan not only for their immediate circumstances but for their future circumstances too. The Zero Energy House was Zero Energy then and continues to be Zero Energy today, even though the family has doubled in size.
Got any questions you want us to answer in the article?
Or use the same button to subscribe and find out when the article is released.