Seems like your WH at 90% efficiency is eligible. Not sure if you get a 30% tax credit off the installed cost or what; check the instructions on the form.
If I can be of any other help, please let me know. Thanks,
Ask your CPA who has all your records who can determine all particulars if you can take a write off
There could be some guidelines as Realtor we not familiar with or professional truly render an opinion
Uncle Sam is also giving away a 30% tax credit, renewable through 2016, of the cost to buy and install a geothermal heat pump, a windmill (residential wind turbine) or a solar energy system (including a solar powered water heater).
There are also rebate programs, which vary by state for replacing old appliances with Energy Star models ($50 to $250), as well as incentives (rewards) for recycling old models. These programs will be in place by April 2010 (see: http://www.energystar.gov).
As always, consult with your tax professional.