The date that separates two arrangements
The Louisiana Public Service Commission changed the rules in September 2019. Customers who installed or applied after December 31, 2019 moved onto the avoided-cost arrangement.
Customers who installed before January 1, 2020 were grandfathered onto full retail net metering for 15 years. After that period their excess is credited at avoided cost like everyone else.
So a pre-2020 array carries a defined remaining term of retail net metering rather than an open-ended benefit, and that term is a specific number worth establishing.
A system installed in 2018, for example, would have its grandfathered period running to some point in the early 2030s. Ask for the installation date and calculate what remains.
What to establish before you agree a price
Ask the seller for the installation and interconnection dates, with documentation rather than a recollection. Those dates place the system on one side of the line or the other.
Ask which arrangement the account is actually on today, and get that confirmed by the utility rather than by the seller. Grandfathered status is only worth something if the account genuinely carries it.
Ask whether the grandfathered status transfers to a new owner, what has to be done to effect that, and by when. An arrangement that does not survive the transaction is worth nothing to you.
Then price accordingly. A pre-2020 array with years of retail net metering left is a materially different asset from an identical array installed last year.
The rest of the diligence on an existing array
Ask for production history rather than an estimate. An installed system has real data, and real data is worth far more than a model.
Ask for the equipment make and model and what warranty remains on the panels, the inverter and the workmanship. Inverters typically have shorter lives than panels, and a pre-2020 system may be approaching a replacement.
Ask about the roof underneath. A system on a roof near the end of its life implies a removal and reinstallation cost that belongs in your purchase arithmetic.
Ask whether the system is owned outright, financed, or on a lease or power purchase agreement. Those are entirely different things to inherit, and only the first is straightforwardly an asset.
What is left to build the number from
For a new system, the 30 percent federal Residential Clean Energy Credit under Section 25D expired for property placed in service after December 31, 2025, and Louisiana state credit expired on December 31, 2017.
Section 48E survives at 30 percent for third-party owners under leases and power purchase agreements.
A new system receives full retail value for what you consume as it is generated and avoided-cost compensation for exports, plus the property tax exemption on the value it adds.
For an existing system, start with the installation date, whether grandfathered status transfers and how many of the 15 years remain. That is the single fact that most changes what the array is worth to you.