Different expert here...
You are asking about Residential Energy Efficient Property Credit which is based on section 25D.
A credit of 30 percent of the expenditures made by a taxpayer during the taxable year for:
qualified solar electric systems;
qualified solar water heaters;
qualified fuel cell property;
qualified small wind energy property; and
qualified geothermal heat pumps.
The credit for expenditures made for qualified fuel cell property is limited to $500 for each one-half kilowatt of capacity of the property; the amounts of the other qualified expenditures eligible for the credit are not limited.
The statute - see here
(a) Allowance of credit
In the case of an individual, there shall be allowed as a credit against the tax imposed by this chapter for the taxable year an amount equal to the sum of—
(1) 30 percent of the qualified solar electric property expenditures made by the taxpayer during such year,
(d)( 2) Qualified solar electric property expenditure
The term “qualified solar electric property expenditure” means an expenditure for property which uses solar energy to generate electricity for use in a dwelling unit located in the United States and used as a residence by the taxpayer.
(e) Special rules
For purposes of this section—
(1) Labor costs
Expenditures for labor costs properly allocable to the onsite preparation, assembly, or original installation of the property described in subsection (d) and for piping or wiring to interconnect such property to the dwelling unit shall be taken into account for purposes of this section.
So - the cost of labor are INCLUDED into calculation of the credit.
Thus if "developers fee" are actually installation cost - that cost is used to calculate the credit.
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