US clean energy investment rallied in 2014, reaching $51.8 billion for the year — including renewables and advanced grid, storage, and electrified transport technologies — bringing the total dollars invested since 2007 up to $386 billion.

This was one of the nuggets from Bloomberg New Energy Finance’s (BNEF) third annual “Sustainable Energy in America Factbook,” which was released earlier this week. The news of increased investment in clean energy came alongside growth throughout the renewable energy, natural gas, and energy efficiency sectors throughout 2014, as well as increased deployment of sustainable energy.

“For the last three years, the Sustainable Energy in America Factbook has documented the revolution transforming how the US produces, delivers, and consumes energy,” wrote this year’s authors, concluding that in 2014, “that revolution continued, and the long-term implications of these changes are coming into sharp focus.”

“The 2015 Factbook clearly shows that America is on the path to a more sustainable energy sector,” said Lisa Jacobson, President of the Business Council for Sustainable Energy, which commissioned the report from Bloomberg. “Our energy productivity is rising along with economic growth, while energy-intensive industries are onshoring production to the United States to take advantage of low energy costs. All of this is happening as investment in clean energy continues to grow and as new natural gas infrastructure continues to come online. These are strong positive signs for America’s economy and environment.”

According to BNEF, the US has seen between $35 and $65 billion worth of clean energy investment each year since 2007. In 2011, levels reached an all-time high of $65.2 billion, and in 2014, clean energy investment reached $51.8 billion, a 7% increase over 2013 levels (but a 20.5% decrease over levels).

Bloomberg New Energy Finance attributes 2014’s investment growth to “the brief window” that opened in the form of the wind energy Production Tax Credit at the end of 2014, and the acceleration of the rooftop solar business. Additionally, BNEF found “the emerging phenomenon of ‘yieldcos’ ” another motivator for 2014’s investment figures.

Yieldcos are popping up more and more of late, publicly listed companies that own operating renewable energy assets, and often directly spun out of a recognizable parent company.

Recently, California-based yieldco Pattern Energy acquired a majority stake in the Tokyo-based renewable energy project developer and operator Green Power Investment Corporation. SunEdison and its own yieldco, TerraForm, recently finalised their acquisition of First Wind, which will provide the yieldco with a number of new projects to develop and maintain.

This is all good news for the clean energy sector in the US, which ranked second highest globally in terms of new dollars attracted for investment (unsurprisingly, China was first). Specifically, the US was the world’s second-largest market for new wind energy installations, behind China (again), and third-largest for solar, behind China (again again) and Japan.