Solar Return On Investment (ROI) really comes down to how you define your “return” as monetary, learning experience, preparation,… Personally it’s been a mix of all these things with a bent to be self reliant.
I’ve played with solar since the 80s. My senior thesis was on a solar power load management controller that monitors power input and output in order to control load shedding, load reactivating, issue warnings, etc. Any power input could be used but flavor of the day back then was for solar power. This was all controlled off of an Intel 8bit microprocessor. First home system was with 4 Carrizo mud used solar panels, 36 12vdc 20ahr gel cell batteries, a pulse width solar controller, and a battery charger. That grew to a kilowatt solar array with VLX 53, Trace modified inverter, power monitoring, higher amperage solar controller, 8 Trojan 6v batteries, transfer switch, …. The solar bug bit me hard! That system just kept upgrading over time. Did I “need” this system? No but I wanted it and it was great to have operational when the 1989 Loma Prieta earthquake hit. Power went down for over a day and we were on a mainline but I still had power thanks to my solar system. Neighbors loved us since we had lights, radio, tv, running fridge, etc. So this system ROI was like an insurance policy, Priceless! Hope you never need it but great to have when you do need it.
Another ROI point of view would be all the various micro solar systems that I’ve built for keeping batteries charged for gate openers, lights in various outbuildings, fans/widow controllers for greenhouses, keeping vehicles/trailer batteries charged, remote cabins, camera systems, etc. ROI here would be the cost to replace the dead batteries to the time to remove and keep the batteries floated elsewhere, to having no power/lights in remote outbuildings. Or it just costs too much to run grid power to where it is needed. One recent example would be I needed power for lights and an automatic door opener/closure on a chicken coop. The coop is roughly 280ft from the nearest grid power source. That electrical power run would cost over $1200 to run power boxes, breakers, outlets, PVC conduit and 8g wire out to it. Simple solution was to use a micro solar system comprised of 1 solar panel, a cheap pulse width charge controller, fusing, and a 7ahr battery. The ROI for this case would be over $1k.
So ROI is variable. Really depends on how you define it. Solar required to have power. Well having power is worth whatever you can afford to install. Solar systems can be like an insurance policy for outages. Worth every penny if actually used to why did I spend so much for something I never used. Solar for fun/knowledge/hobby really makes ROI meaningless. ROI by selling solar power back to the utilities as a private party, not a very wise investment. There are better investments with much higher ROI than being a power provider to the local utility. After all, the most money to be made in solar is on the financial side aka selling solar to servicing the debt.
