NIWA has developed a web-based calculator to provide information on solar energy availability anywhere in New Zealand.
SolarView is a DIY tool, designed to enable anyone in New Zealand to estimate how much solar energy their house could capture, at any time of year. The system uses Google maps and climate data to estimate the available solar energy at a particular location. The calculations take into account local topography (landscape), orientation of the proposed solar panels, and then obstructions such as buildings and trees.
Actual energy savings will depend on the type of panels installed and their efficiency. The SolarView service will soon be extended to allow evaluation of different types of solar panels.
Click on the image below to see a SolarView of a site in Central Otago. The different coloured arcs show the sun's track at different times of year.
SolarView determines the total amount of energy delivered by the sun to a one metre square (m²) surface during each day. As you follow the path of the sun from east to west (right to left) across the diagram, the time of day is labeled (below the curve), along with the cumulative energy received in kWh/m² (above the curve) up until that point.
You can calculate the the available solar energy for that date by taking the energy total at the time where the sun sets (where the sun path line crosses the horizon on the landscape image) and subtracting the total energy at the point where the sun rises.
Just remember that the values indicate the amount of energy hitting the solar device - not how much of this energy would be converted into heat or electricity.