Solar's contribution to the Zero Energy goal
The average Auckland house consumes 7,970 kWh of electricity from the grid each year1, with 30% used for heating. The Zero Energy House building envelope (framing, insulation, and glazing) eliminates the need for heating, effectively getting us 30% of the way towards our Zero Energy goal.
Solar takes care of the rest. The solar water heating system contributes 25% by providing almost all of our water heating needs. The last 45% is met by the solar photovoltaic (PV) panels, which generate enough electricity to power all of the appliances and lights in the house and run the hot water cylinder for the remaining water heating needs.
Why we went solar
The choice to go solar is tightly linked with the reasons why we've chosen to pursue Zero Energy. Building a house like this protects two things:
The average Auckland family could pay $80,000 in electricity bills over a 25-year period. Our solar system cost a fraction of that.
- The environment. Most of the country's electricity supply comes from hydro-electric power, with a portion coming from coal-powered plants. Coal pollutes the atmosphere and hydro-electric power requires infrastructure that infringes on the natural environment. And, regardless of the source, electricity gets shifted all around the country on a massive transmission grid that costs money to maintain and results in energy loss. Generating electricity via solar on-site is clean, efficient, and, we believe, elegant.
- Our finances. When you factor in long-term electricity costs solar makes financial sense. The average Auckland home pays $2,000 a year in electricity bills2, equating to $50,000 over a 25-year period. But that doesn't take into account energy price increases. Since 2000 inflation-adjusted prices have risen by 3% per annum3. If they continue to do so the average home could face $80,000 in electricity bills over a 25-year period; our solar system cost a fraction of that.
What the solar roof looks like
On a typical house the roof is there simply for protection from the elements. We decided to make our roof work for us. With our architects we designed the roof size, shape, and pitch (along with orientation and placement of the entire building) to capture the amount of solar energy we needed to achieve our Zero Energy goal.
This has resulted in the entire north-facing side of the roof being covered in energy-generating panels. Eight solar water heating panels are lined up in a row along the ridgeline, and an array of eighty-eight photovoltaic panels cover the remainder of the roof.
Using both systems means we can meet all of our energy needs. Heating water with a solar hot water system is far more efficient than doing so via electricity generated from PV so it is important to have both.
Systems selected and their performance
More detail is available at the following pages:
- Photovoltaics (PV). Discusses different types of PV panels, why we selected the system we installed, and its expected performance over a year.
- Solar Water Heating. Looks at the two main types of solar water heating systems, why we chose our system, and expected annual performance.
- Energy Performance. Presents real-time feeds of both system's current performance, along with analysis of past data and comparison with modelled performance. This page will be started in October 2013, updated regularly with content, and then a full year's analysis will be presented in late summer 2014.
1 Building Research Association New Zealand (BRANZ). (2006). Energy use in New Zealand households: Report on the year 10 analysis for the household energy end-use project (HEEP). p18.
2 This is based on the 2010 rate of 25.5c per kWh in, Ministry of Economic Development. (2011). New Zealand energy data file: 2010 calendar year edition. p130-131.
3 Based on calculations from data in the MED report above. The non-adjusted average annual increase is 7%, as we state in the video.