As the calendar continues ticking on a vital renewable energy tax credit set to expire in two weeks, 24 U.S. senators sent a letter to the Senate Committee on Finance in hopes of preserving jobs, investments and a path to clean energy.

While the renewable energy Production Tax Credit (PTC) and its Dec. 31 expiration date is most dire, the senators' letter includes nine other policies related to renewable energy, green building and efficient transportation the group would like to see extended sooner than later.

"If a broader tax code overhaul cannot be achieved by year’s end, it is imperative that these key clean energy tax incentives are renewed as soon as possible," the letter reads. "In recent years, provisions like the production tax credit and the investment tax credit have helped technologies like wind and solar create tens of thousands of American jobs and generate an increasing share of America’s power.

"These tax credits have helped scale up production and drive down the cost of clean energy technologies. They remain critical to addressing the market failures that prevent cost-effective, market-ready technologies from being deployed to their full potential."

The senators who signed the letter represent a variety of states, ranging from those with renewable energy A-grades like Oregon and New Mexico to those with C- and D-ratings like energy like Minnesota and New Hampshire. Here's a rundown on three of the policies they want to see extended, as described in the letter:

• PTC: Set to expire at the end of the year, the PTC supports investments in wind, biomass, hydropower and more. The credit drove $25 billion in private investment last year in the wind industry alone. It led to the installation of more than 13 gigawatts of new production capacity, which is enough to power more than 3 million American homes. According to the senators, expiration would threaten more than 80,000 jobs in most states.

• Investment Tax Credit (ITC): This tax credit supports solar energy generation, small wind projects, fuel cells and more. Under current law, an offshore wind project will also be eligible for the ITC if that project commences construction before the end of 2013. There are currently no offshore wind facilities operating in U.S. waters. "A long-term extension of the ITC for offshore wind is needed to jumpstart this industry," the letter reads. "Additionally, changing the applicability of the ITC from projects that are operational by the expiration date to projects that have commenced construction would make the tax credit consistent with the PTC and help drive the deployment of thousands of megawatts of additional new solar capacity. This change would allow the American solar industry, which has grown from 15,000 employees in 2005 to 120,000 today, to continue creating jobs in the U.S."

• Advanced Energy Manufacturing Tax Credit. The four-year-old credit drove $5.4 billion in private investments in 183 new, expanded or re-equipped clean energy manufacturing projects throughout the nation. More than 40,000 new manufacturing jobs were created as a result. The program has not garnered any new funding since it was created.

"With continued support, clean energy will help Americans save money on their energy bills and reduce harmful pollution," according to the senators. "Clean energy tax incentives are critical to ensuring that American consumers have access to clean, low-cost energy and critical to keeping American businesses and workers competitive in this key growth sector of the global economy.

"We urge you to include these incentives in any tax extender package that the Senate considers."

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