Compare equivalent project options
A solar traffic signal investment should be compared with an alternative that meets the same operating and availability requirements. Include the actual site constraints. Solar power is not automatically the least-cost option for every installation.
Build a documented cost model
Separate equipment, civil works, utility connection, installation and commissioning costs. Then include inspection, cleaning, battery replacement, other maintenance and disposal where applicable. Record the source and date of each price and the items excluded from each quotation.
Estimate recurring savings carefully
Use the proposed load profile and local electricity tariff. Include fixed utility charges only where they apply. Avoid counting the same benefit twice, such as treating avoided cable works as both an initial saving and an annual saving.
Calculate payback with explicit assumptions
Simple payback divides additional initial investment by positive net annual savings. It is not meaningful when net savings are zero or negative, and it ignores the timing of later costs. For a discounted comparison, define the analysis period, discount rate and replacement schedule.
Test uncertainty before deciding
Compare scenarios for solar availability, battery life, maintenance costs and energy prices. Include only defensible outage costs and state how they were estimated. Present the assumptions and sensitivity range alongside the result rather than promising a universal payback period.