As always, the disclaimer first...talk to your tax advisor to be sure.
I read somewhere (I think it was an IRS publication) that you cannot take
the tax credit until the system is operating. If my recollection is
accurate, you would not be able to take the tax credit for the deposit on
your 2011 taxes and you would take the tax credit for the entire system cost
net of grants on your 2012 taxes.
Hope this helps.
Jim Elkind
(m) 508-517-0800