It is 20% of the Federal Tax Credit or in your example, 20% of the $9,000 or $1,800 IA credit or the state tax credit is equal to 6% of the system cost ($30,000 * 6% = $1,800).
Per http://www.geothermalgenius.org/states/iowa/ IOWA AND GEOTHERMAL: Geothermal heating and cooling is a proven and reliable method of delivering energy efficient, environmentally friendly heating and cooling to Iowa homes by using the earth's constant ground temperature to provide heating, cooling and hot water in both new and retrofit construction. There is a 30% Federal Tax Credit AND a 20% Iowa State Tax Credit, not a bad incentive!
On May 25, 2012, Iowa Governor Terry Branstad signed SF 2342 into law which enacted a series of Iowa tax incentives for residential geothermal incentives. Geothermal heat pumps installed on residential property in Iowa are eligible for a tax credit equal to 20% of the Federal Tax Credit. Because the federal tax credit is set at 30%, the state tax credit is equal to 6% of the system cost . Any credit in excess of the tax payer's liability may be carried forward for up to 10 years. The credit may be applied retroactively to systems installed beginning January 1, 2012. The Iowa Department of Revenue must issue rules for implementing the credit.
