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TL;DR
ROI is an investment return over a defined period. Payback measures the time needed to recover the initial cost. Both indicators must account for project costs and income.
Definition
ROI expresses net investment profit relative to invested capital over a defined period, as a percentage. It differs from payback, expressed in years.
ROI
% over a period
Payback
Years
Investment
Full net cost
Annual cash flows
Income less costs
For simple payback, divide net initial cost by an assumed constant annual net cash flow. This includes avoided purchases and export income, less maintenance and other costs. If cash flows change, accumulate them year by year, including losses, replacements and operating life. This simple calculation omits discounting; a full financial analysis can include it.
Use the full quote, confirmed grants and applicable tax treatment. Use the purchase tariff actually avoided and the export contract for your address. Compare several output, self-consumption and tariff scenarios; the canton alone does not guarantee payback.
Related guides
The calculator gives an initial estimate. For a decision, document full cost, grants, hourly consumption, tariffs, fees and replacements. Request payback and return over the chosen period separately.
A higher avoided purchase tariff can increase the value of electricity consumed on site. The result also depends on export prices, volumes, costs and timing. Simulate higher, stable and lower tariffs rather than assuming a guaranteed trend.
Sources & method
Check equipment values in the offered model’s datasheet and warranty terms. Confirm grant, permit and connection requirements with the responsible programme, municipality and grid operator.
This content is for information only. For your project, verify prices, grants, timelines, permissions and expected returns with the relevant authorities, grid operator and installer, and check the applicable contracts.
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Estimate output, avoided purchases and payback using your data. Confirm the assumptions in a quote.
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