Centralised control of New Zealand’s hydro, solar and wind power and storage is the only way to reduce energy emissions, Dr Kevin Trenberth argues on Newsroom. In Germany, with about 20% less sunshine than New Zealand, 1.3 million homes generate 4,900 MW of power (8.2% of their total). In NZ, some 19,500 homes generate an estimated 68 MW (1%). In many countries, extra power not used from rooftop solar at the site is sent to the power company and recovered later when needed, at no cost. Here, the cost of buying the power back is a lot higher – a major disincentive to install solar.