The terms are set per utility
The Indiana Utility Regulatory Commission sets the Excess Distributed Generation credit using a formula, the prior year average wholesale cost of electricity plus 25 percent, but the resulting figure is set for each utility rather than as a single statewide number.
The netting method also varies. The Indiana Supreme Court permitted a utility to use instantaneous netting, but it did not require every utility to adopt it, so some may still net across a billing period.
Those two variables together determine most of what your system will be worth, and neither is visible from a statewide guide.
So check the utility name on a recent bill, then take two specific questions to that utility: what is the current Excess Distributed Generation credit, and is excess generation measured instantaneously or across the billing period.
Getting the answers from the right source
Ask the utility rather than the installer, and ask for the answers in writing where you can. The utility is the organisation that will administer your account and set your credit.
Then take those answers back to the quote. Ask which credit rate and which netting method the projection assumed, and reconcile them against what the utility told you.
If they do not match, ask for the projection to be rebuilt rather than explained. A discrepancy between a quote and the utility own statement is the most useful thing you can find at this stage.
Ask also what the interconnection process involves, what it costs, and how long it takes with your specific utility. Practice varies and the gap between installation and permission to operate is where most project frustration lives.
The design follows from those two answers
If your utility nets instantaneously, self-consumption is overwhelmingly dominant and the design should be built around your daytime load, with load shifting and possibly storage doing real work.
If it nets across a billing period, midday generation offsets evening consumption within the month before any export is calculated, which softens the impact of the low credit considerably.
Either way the export credit is well below retail, so a system sized to annual consumption will still send a meaningful share of its output out at the low rate.
Ask for the design built from your consumption pattern with the confirmed netting method applied, and for a smaller system modelled alongside so you can compare returns directly.
Building the number from what Indiana still offers
The 30 percent federal Residential Clean Energy Credit under Section 25D expired for property placed in service after December 31, 2025, so a cash or loan purchase in Hammond receives no federal tax credit, and Indiana has no state income tax credit for solar.
Section 48E survives at 30 percent for third-party owners under leases and power purchase agreements, so ask what a provider claims and what reaches you in the rate.
What exists is the 7 percent sales tax exemption, the property tax exemption on added value, retail value for self-consumed generation, and your utility own Excess Distributed Generation credit under its own netting method.
Confirm those last two with the utility in writing, then ask for the projection rebuilt on them rather than on a statewide assumption.