Hydro currently provides around 60% of New Zealand's electricity, while fossil fuels such as coal, gas and oil, provide around 30%. Unlike electricity generated from fossil fuels, the use of wind doesn't generate any greenhouse gases.
Wind is one of the fastest forms of electricity generation to build and bring online, once the appropriate resource consents have been obtained. It generally also has one of the lowest overall environmental impacts. Wind is actually a form of solar energy, the earth's most fundamental renewable energy source. Wind is created by the sun heating various parts of the earth's surface to different temperatures, combined with the rotation of the earth.
Best of all, wind energy is abundant. In fact, New Zealand has one of the best wind energy resources in the world.