A new tool is available to help Auckland households and businesses work out whether it makes financial sense to install solar panels on their roofs.
The free online calculator factors in the unique “solar rooftop potential” of half a million Auckland buildings down to one square metre.
This potential depends on such things as the roof’s slope and aspect, and shade from surrounding buildings and trees.
“Solar generation is rapidly rising in New Zealand, with homes leading the trend. We wanted to offer an educational tool that is impartial and realistic to help people work out if solar is economic for their households or workplaces,” says Dr Kiti Suomalainen, a research fellow at the University of Auckland Business School’s Energy Centre.
New Zealand’s total installed solar capacity rose fivefold over the three years to 2017, and Auckland Council has a goal of 970 MW installed capacity of solar photovoltaics by 2040.
Suomalainen devised the geographical 3D computer modelling behind the calculator.
She used LiDAR data from Auckland Council, which is collected by planes emitting light pulses and timing how long it took for the reflected pulse to return to the plane, to construct a digital 3D model of the city with all its buildings and trees and other objects. With this, the solar radiation on individual rooftops could be calculated.
The calculator allows users to zoom in on their rooftop for a colour-coded view of its solar energy potential, which highlights the best spots to place panels.
You can also enter the size and quality solar panel you prefer, how much solar power you would use and how much you would sell back to the grid, and several other values.
The calculator gives the total value (savings and revenues minus costs) of the installation over its lifetime. If it is positive, it’s a good investment.
Dr Suomalainen suggests visiting seanz.org.nz (Sustainable Electricity Association New Zealand) for a directory of accredited solar panel suppliers.
“Self-consumption rate – the percentage of solar power that you use yourself, rather than sell back to the grid – is the main thing that will affect your economics,” she says.
“If you’re at home all day you will probably use more power than someone who is at work or school most of the day.
“For every kilowatt-hour of solar power you use, you save about 27 cents.
“The buy-back rate at the moment is around 8 cents – so the more you use, the greater the overall value of your solar generation.”
The calculator is now at a stage where users can test it and report any issues (e.g. mismatch of solar potential and underlying building on the map due to outdated building data).
Suomalainen welcomes feedback in order to make the tool as user-friendly and accurate as possible.
Try out the calculator here.