Windows. Not all Energy Star windows are eligible for the federal tax credits widely advertised by manufacturers. Windows must have U-factor rating of 0.30 or less and a solar heat gain coefficient (SHGC) of 0.30 or less. Keep copies of records for your clients.
HVAC and water heaters. As with windows, not all HVAC units and water heaters qualify for the federal tax credit. See the requirements at this link: http://www.energystar.gov/index.cfm?c=tax_credits.tx_index.
Roofs. As unsexy as roofs may seem in the world of energy efficiency, many roofs — including some three-tab and architectural shingles — can qualify for the federal tax credit. They achieve Energy Star ratings because they reflect and/or shed the sun’s heat, thereby reducing cooling loads. Use the Energy Star link above.