When your utility approves your interconnection, an installation commonly lasts 1 to three times for residential rooftop; more time for ground mount. Monthly bill credits reset on March 31 of on a yearly basis, however, you won’t lose any remaining credits. Rather, it's credited on your account for later use. https://solarsystemaustralia.mystrikingly.com/blog/high-performance-solar-systems-for-homes-and-businesses