How Long Does a Solar Power System Take to Pay Back?

• For grid-connected sites measured against the utility tariff, commercial and industrial systems typically pay back in 3–5 years.
• For off-grid or weak-grid sites measured against diesel generation, payback is often under 18 months, because the real cost of diesel is far higher than the pump price suggests.
• A credible calculation must include fuel, fuel transport, genset servicing and replacement, and the production lost during outages — the last of these is usually the largest number.
• Batteries specified at 6,000+ cycles and 90–95% depth of discharge typically cover 8–12 hours of overnight commercial load on a single charge.
• The three variables that move payback most are the local tariff or delivered diesel cost, the daily load curve, and how many hours of backup you actually need.