Last week, the United Nations announced that enough countries have ratified the landmark Paris Agreement to curb climate change that it will enter into force in early November. This is a major step forward, and I am thrilled at the global leadership that is so critical to the goals we are trying to achieve in our Climate and Clean Energy program. It is the first time that all major emitters, including the United States, China, and India, have joined with long-time leaders, such as the European Union, to both recognize the urgency of addressing climate change and to commit to curb pollution.
This swift ratification of the Paris Agreement provides valuable momentum as countries gather this week to discuss a possible amendment to the Montreal Protocol to phase out hydro-fluorocarbons, a potent greenhouse gas. An ambitious amendment would capture the next single greatest opportunity to tackle climate change. The Heising-Simons Foundation recently joined a group of 19 philanthropic donors to support energy efficiency efforts that complement the rapid phase-out of this gas, while helping countries meet their commitments under the Paris Agreement, and saving families and businesses money on their electric bills.
Likewise, we are so proud of our grantees working on the research and advocacy that will enable the United States to do its part in the global effort to curb climate change. While much work remains, there are already numerous signs of progress.
Greenhouse gas emissions in the U.S. have dropped 9 percent in the last decade, thanks in large part to a cleaner electricity sector. Major improvements in energy efficiency save consumers $90 billion annually on electric bills and have helped demand for electricity level-off, even as the economy continues to grow. The cost of solar power has dropped in half since 2008, and installed capacity increased ten-fold, thanks in part to the more than 1 million households and businesses who have installed solar panels. States are retiring old, polluting coal-fired power plants that have been the number one source of pollution in the nation. And the Clean Power Plan promises to help every state modernize its electric system to be cleaner and more efficient.
Leaders like California are showing the way to double down on this progress. The state recently strengthened its pollution limit to reach 40 percent below 1990 levels by 2030, building on its goals to double energy efficiency and get half of its electricity from renewables in that timeframe. With global leaders ready to curb pollution and advance clean energy to meet the Paris Agreement, we will continue to seek opportunities to support the trailblazers that can light the way forward.