Itc basis updates

[brtietz]

Pull Request Template

Description

Add new functionality to specify ITC and depreciation bases by technology installed cost. Update defaults to match post OBBBA phase outs (for projects that start construction after July 4th 2026 and don't enter operation before Dec 31 2026). Add bonus depreciation.

Help updates will be completed in parallel with feature reviews.

Expect many negative NPVs. PPA prices will be updated in a future PR. Time permitting, commercial depreciation will be updated in a future PR.

References:
-General: https://fbtgibbons.com/one-big-beautiful-bill-act-cuts-the-power-phase%e2%80%91outs-foreign%e2%80%91entity-restrictions-and-domestic-content-in-clean%e2%80%91energy-credits/

• Linking depreciation allocation to ITC basis: https://www.mcguirewoods.com/client-resources/alerts/2025/7/tax-bill-enacted-on-july-4-2025-contains-scaled-back-renewable-energy-provisions/
• Bonus depreciation allocations: https://www.bassets.net/blog/obbba-depreciation-2025-2026-guide and https://blog.harvestsolar.com/harvest-solar-blog-2024/major-solar-depreciation-changes-under-the-obbb-what-business-owners-need-to-know
• Which technologies retain tax credits: https://natlawreview.com/article/obbba-major-shift-federal-clean-energy-tax-incentives and https://www.fuelcellenergy.com/blog/the-one-big-beautiful-bill-act-is-a-win-for-clean-energy-and-for-america

Corresponding branches and PRs:

itc_basis_updates on ssc (NatLabRockies/ssc#1395)

Develop on other branches.

Unit Test Impact:

Test results changed due to tax credit defaults and default depreciation bases changes.

Checklist

• requires help revision and I added that label
• adds, removes, modifies, or deletes variables in existing compute modules
• adds a new compute module
• changes defaults
• I've tagged this PR to a milestone