Costs for solar thermal energy will be cheaper than coal as soon as 2020, according to a report from the US Department of Energy, making one solar ETF a great way to profit.

Google, Chevron and Goldman are all betting that this prediction is correct. This from Bloomberg:

Unlike photovoltaic solar panels that convert sunlight to electricity, solar thermal focuses sunrays with mirrors to heat oil in glass pipes to about 700 degrees Fahrenheit (370 degrees Celsius). The oil turns water to steam, which spins an electric turbine. A solar thermal unit that begins operation in 2010 will produce power at 14.2 cents a kilowatt hour, almost triple the 4.8 cents for a plant using pulverized coal, the Energy Information Administration estimates.

Costs for solar thermal may fall as low as 3.5 cents a kilowatt hour by 2020, according to a report commissioned by the U.S. Energy Department. Meanwhile, coal expenses may rise. Congress is considering limits on carbon dioxide and other greenhouse gas emissions. The purchase of pollution permits may be required under a measure the Senate will begin debating next month.

Chevron, Goldman Sachs, FPL, PG&E and other companies have filed more than 50 applications with the Bureau of Land Management to lease government-owned desert property for solar power systems … Google’s philanthropic division put $10 million into eSolar, a start-up in Pasadena, California. Dan Reicher, a former Energy Department official who manages the unit’s climate and energy initiatives, said there will be more such investments.

The PowerShares Clean Energy ETF (PBW) has more than $1.5bn in assets and is one of the most popular ways to invest in solar, biomass, wind, and geothermal energy, says Brian Hunt in Daily Wealth.

“Common sense tells us when the holy trinity of fossil fuels – crude oil, coal, and natural gas – rise in price, companies that provide cleaner substitutes should also rise in price.

“PBW’s only been around for three years […] But with oil approaching $130 a barrel and clean energy stocks out of favor, expect a rally from the ‘treehugger-approved’ companies of the world.”

“Solar panels won’t be accepted en masse unless the economics of it makes sense,” says Charles Delvalle in Investor’s Daily Edge. “Sure, adoption is growing. But it won’t be mainstream until everyone can afford it. The same goes for wind power.

“With so many solutions not making any economic sense, why is adoption skyrocketing? You can thank the government and their incentives. States are ramping up incentives for clean energy production (like California’s $3.3 billion solar initiative). If it weren’t for government incentives adoption would drastically drop.

“When you combine these government incentives with the whole culture change that’s going on, you have a recipe for amazing growth.”