Price does not explain the whole design
A low price alone does not prove that a system will fail. The concern is what was left out to reach that price: assessment, appropriate components, workmanship, protection, commissioning or future maintenance. No universal two-year failure timeline applies to every installation.
Ask what has been checked
A useful proposal explains the load requirement and site constraints, rather than listing only panels, an inverter and a battery. Ask how operating hours, shading, installation conditions and electrical integration were considered.
Request the basis for the design, relevant equipment documentation and the scope of testing. The installation and protection should be reviewed by qualified professionals; visual appearance is not evidence that electrical work is safe.
Plan for the operating years
A system needs an operating plan as well as an installation plan. Documentation, inspection, maintenance and monitoring help identify issues and maintain performance. Clarify what support is included, what is chargeable and who to contact when performance changes.
Compare proposals on a consistent scope. A clear, documented design is more informative than an unsupported promise of unlimited backup or guaranteed savings.