As world leaders from industrial giants and developing nations alike pack their bags for the Rio+20 Earth Summit later this month, the Natural Resources Defense Council used the opportunity to examine how G20 nations are faring on both renewable generation and clean energy investment.

Even as many of the renewables industries struggle through a slowdown period exacerbated by a global economic malaise, a broader view shows a decade of consistent growth and persistent investment. The optimism, however, remains tempered as clean energy still represents a small fraction of global energy consumption.  

A look at the clean energy portfolios in the G20 nations paints a picture of resilience built on the back of wind, solar, geothermal and tidal energy investments. According to the NRDC report, G20 nations have seen a 600 percent increase in clean energy investment since 2004, a rate that far outpaces growth in their overall economies. The European Union has seen the highest level of investment, followed by the United States and China.

While investment is growing, the clean energy sector is still struggling to carve out a larger slice of the overall energy mix. Since 2002, the amount of wind, solar, geothermal, tidal and wave power integrated into the grids of the G20 nations has grown three-fold. But this represents just 2.6 percent of the those nations’ total energy consumption. With the current rate of growth, that would equal less than 4 percent of total consumption by 2015 and about 6 percent by 2020. Of course, consumption itself is expected to grow, so any reductions in carbon emissions are quickly negated.

So to make real inroads in clean energy installation — and significant decreases in carbon emissions — NRDC has created a list of guiding principles for each of the G20 representatives to bring to the table in Rio. These include tangible plans to pass laws that would require at least 15 percent of their energy is produced from renewable sources by 2015; strong commitments to create a framework for cooperation between countries that would help achieve the 15 percent goal; and monitoring provisions that will ensure the guidelines are clear and the targets are met.

Below is a series of charts that details electricity and clean energy investments made for the G20 nations.