I think it depends on the type of system:
- A recent Enphase system with 25-year warranties on both the PV panels and the microinverters, both with very high MTBFs, should have near zero maintenance costs and will provide value for a long time to come, so it should add value.
- A grid-tied system with a SunnyBoy central inverter might have a neutral value since it provides value, but will likely need all inverters replaced approximately 10 years after the system was installed.
- An off-grid PV system may have a negative value for someone who does not wish to maintain a PV system.