An outlook report by a leading international finance group says Australia will sink billions more into solar energy over the next fifteen years.

Forecasts in Bloomberg New Energy Finance’s Market 2030 outlook suggest Australia could spend around $55 billion on new electricity between now and 2030, and it estimates two thirds will be in the form of solar technology.

Nearly half the solar investment will be in the form of rooftop panels, if current trends continue.

The Bloomberg report includes detailed forecasts for Australia and Asia, and some suggest it could have major implications for the coal exporters and domestic generators.

The estimations are based on an outlook with the Renewable Energy target in place, but do not factor any future improvement in efficiency or price of renewable energy sources.

Even with no subsidies and no carbon price, the economists say the payback for a rooftop solar system will halve by 2030. At that point, most systems will pay for themselves three years after they are installed.

“Australia, like Japan, has high retail electricity prices which, combined with continuously reducing technology costs, are the main reasons for the small-scale PV adoption rate,” Bloomberg economists write.

“The favourable economics of the small-scale PV technology – ie, the reduction in payback period – will drive the sixfold increase in small-scale PV capacity and the technology’s contribution to total capacity additions between 2013 and 2030.”

The forecasts do assume the retention of the Renewable Energy Target, which is far from assured, and other policies affecting deployment of large-scale renewable power systems.

Bloomberg predicts nearly 8GW of utility-scale photo-voltaic power will be built by 2030, if the RET is maintained, will 6.4GW of wind power.

Bloomberg New Energy Finance sees coal dropping as a proportion of Australia’s total generation capacity.

Figures suggest it will fall from 45 per cent of the total capacity in 2013, down to 27 per cent by 2030.

Gas is predicted to drop too, falling from 30 per cent to 23 per cent.

On the other hand, the economists see renewable capacity increasing from 24 per cent to 48 per cent. They say wind will rise from 5 per cent to 10 per cent and solar from 5 per cent to 29 per cent of total capacity.