V Power · Solar Knowledge Centre
Solar ROI, Generation & Payback in Kerala
Understand the assumptions behind savings before comparing solar with future electricity spending.
By V Power Solar Solutions · Last updated
What do generation examples mean?
Generation is measured in kilowatt-hours (kWh), also called units. System capacity in kilowatts (kW) is not the same as annual electricity production. Using this site’s illustrative 1,450 kWh per kW per year assumption gives the following first-year figures.
| Capacity | Annual generation example | Monthly average example |
|---|---|---|
| 3 kW | 4,350 kWh | 363 kWh |
| 5 kW | 7,250 kWh | 604 kWh |
| 10 kW | 14,500 kWh | 1208 kWh |
These are arithmetic examples, not site forecasts. Monthly production varies; shading, orientation, weather, equipment and downtime affect actual output.
How the calculator works
It converts a bill to estimated units using the stated tariff, or uses units directly if you have them. It estimates capacity from annual consumption, then limits it where roof area is supplied. Annual valued energy is capped at annual consumption, so the model does not assume unlimited paid export.
For each year, generation declines by the configured degradation rate and the value of electricity changes with the tariff assumption. Maintenance and any configured replacement allowance are deducted. Cumulative net operating savings are compared with the initial investment after selected assistance.
Payback, savings and ROI are different
| Measure | Meaning |
|---|---|
| Simple payback | Net investment divided by first-year net operating savings. It ignores later changes. |
| Chart break-even | When modelled cumulative net operating savings first reach the net investment. |
| 10- and 25-year savings | Cumulative operating savings after maintenance and configured replacements; initial investment is shown separately. |
| Net benefit | Cumulative operating savings minus the initial net investment. |
| ROI | Net benefit divided by net investment, expressed as a percentage; not an annualised return. |
Test the assumptions that matter
A higher electricity tariff improves projected savings, while shading and downtime reduce generation. Maintenance, inverter replacement, batteries and borrowing costs can change the result. The calculator does not include loan interest, taxes, discounting or a detailed battery dispatch model. A zero replacement allowance means replacements are excluded, not that none will be needed.
Compare both subsidy options and inspect the annual table. The interactive chart gives a useful planning view, but the investment decision should use a site-specific proposal.