The age of the home should not impact the installation. The system is more dependent on your yard space for where the underground pipes will run. The condition of your ductwork may also play a part in the installation.

As for tax credits and rebates, Maryland's Geothermal Heat Pump Grant, may help you cover up to $2,000 of the cost of a new geothermal heat pump. The rebate is given for $500 per ton of refrigeration capacity.

Additionally, Maryland does not charge sales tax for geothermal heat pumps, and the system will not cause your property taxes to go up.

Finally, the federal government will cover up to 30 percent of the cost geothermal heat pumps through a federal Residential Renewable Energy Tax Credit. If you don't use the entire credit, you can carry forward any remaining credit to future tax years through 2016.