There is no universal payback period for a solar installation. The result depends on roof production, how much electricity you use as it is generated, purchase prices, export-credit terms and the project’s full cost.
Start with your consumption data
Use bills and, where available, hourly consumption data from several months. Separate self-consumed electricity from imports and exports. An estimate based only on annual use may overstate savings.
Include all costs and scenarios
Compare quotes using the same estimated production and itemise equipment, installation, paperwork, financing and expected maintenance. Model different electricity prices and usage patterns; show the base case separately from any incentive whose call and eligibility you have verified.
Be cautious with guaranteed savings claims
Actual savings can differ from a model because of weather, household use, prices and export credits. Ask for assumptions in writing, review warranties and compare the quote with your own bills before deciding.