It affects the geothermal producers. As the expression goes, “We need to talk.”

I have argued over and over that in an energy-short future, geothermal power will play a key role in meeting power needs. Geothermal systems are well-known technology, at least to people who follow the technology. And some geothermal fields have been making power for many decades. So there’s a real track record for geothermal, unlike for many other alleged technological “solutions” to the energy problems of our time.

Geothermal offers some unique benefits. It is “clean,” emitting essentially no carbon dioxide (CO2). Plus, geothermal comes with its own fuel supply, namely the heat of the Earth. That is, once you drill the wells, you don’t have to buy coal or oil or natural gas over the decades of operation. In essence, when you set up a geothermal power system, you are “buying” not just the installation, but also the fuel upfront.

Keep that last point in mind. Geothermal has higher upfront capital costs. But it has far lower operational costs over the life of the project. It’s like buying a car and never having to buy any more gasoline.

So geothermal works. But like most good things in life, it requires a specific skill set up and down the industrial ladder.

And there is no geothermal fairy waving a magic wand and ZAP, you have electrons in the grid. From exploration to drilling to development to spinning turbines, you have to know what you are doing in the geothermal field. This includes accounting for the costs of operation and production.

OK, here is the issue. Under current U.S. tax law, a power producer gets an income tax credit (called a “production tax credit,” or PTC) for producing electricity using renewable energy resources. This includes geothermal, as well as wind, biomass, low-head hydropower, landfill gas and even trash combustion.

The PTC is a key part of the economics of geothermal. The prospect of the eventual PTC helps get projects funded and developed. The PTC helps overcome the higher upfront capital costs to drill into the Earth’s hot spots.

So the PTC offers some serious incentive for geothermal development. A taxpayer can claim the PTC for 10 years, beginning on the date the qualified facility is placed in service. But under current tax law, in order to qualify for the credit, the geothermal facilities must be placed in service by Dec. 31, 2008.

In the past, Congress has set the PTC to last for two years, and has renewed it periodically. When Congress has not renewed the PRC, investment in renewable energy systems has crashed the next year. See how in this graph (Page 19 of 29).

Do you see the pattern? Boom-crash. Boom-crash. Boom-crash. Then Congress extended the PTC in 2006, so the installed base of power systems began to take off in the past couple years.