Is Rooftop Solar Worth It in India? A Worksheet

To decide is rooftop solar worth it in India, build a worksheet from the actual bill, roof, grid process, itemised quote, generation model, self-consumption, export treatment, finance, maintenance, and replacement scenarios. Run conservative, expected, and favourable cases. If the decision changes with one optimistic assumption, it is not yet robust.

This page provides the structure, formulas, and evidence checks. It does not publish a universal system price, saving, payback period, tariff, subsidy outcome, or investment return.

Which household and site conditions determine whether solar is worth it?

The decision depends on usable roof area, shading and structure, grid connection, electricity-use pattern, tariff components, expected ownership period, installation quote, generation evidence, self-consumption, export rules, finance, maintenance, and replacement exposure. A high bill alone does not prove suitability, and a sunny roof alone does not prove financial value.

Record these inputs before calculating:

For tenants, shared roofs, shaded sites, short ownership periods, disputed roof rights, or uncertain grid approval, resolve the constraint before relying on a payback figure.

How should electricity-bill savings be calculated?

Calculate avoided import and export value separately. Self-consumed solar can avoid the variable bill components that would otherwise apply to those units, while exported energy follows the current metering and credit rule. Fixed, demand, minimum, tax, duty, time-of-use, and other charges may behave differently and need line-by-line treatment.

Use these worksheet relationships with consistent units:

• self-consumed solar energy = solar generation used onsite before export
• exported solar energy = eligible generation sent through the approved export arrangement
• avoided import value = self-consumed energy × applicable avoided import charge
• export value = eligible exported energy × applicable export credit
• gross annual electricity value = avoided import value + export value

Ask the modeller to identify the source date and jurisdiction for every rate. The net-metering guide explains why a national rule cannot replace the applicable state and DISCOM documents.

How should generation, self-consumption and export be modelled?

Use a site-specific generation model with declared weather source, shading, orientation, equipment, losses, availability, degradation basis, and uncertainty. Then align generation with the household’s time-of-use load to estimate self-consumption and export. Annual consumption alone cannot show when solar is used onsite or sent to the grid.

Request:

1. array layout and usable capacity;
2. weather or irradiation source and observation period;
3. shading method and obstruction assumptions;
4. module and inverter models used in the simulation;
5. DC, conversion, wiring, mismatch, temperature, clipping and availability assumptions;
6. monthly generation output, not only one annual number;
7. load profile or documented proxy used for self-consumption; and
8. uncertainty or sensitivity range around the expected case.

If the household expects an EV, air conditioner, battery, business load, vacancy, or working-pattern change, model it as a separate case. Do not quietly put a future load into the base case to make solar appear better.

Which project costs and assistance belong in the worksheet?

Include every contracted and reasonably foreseeable cash flow, with source and timing. Separate the installed solar scope from optional battery, finance, insurance, monitoring, service, maintenance, repairs, replacements, application or metering items, taxes, and exclusions. Record government assistance as a conditional inflow until eligibility and receipt are confirmed.

Use a cost ledger:

The solar quotation checklist helps expose omitted scope. The PM Surya Ghar guide provides the current central residential framework but must be rechecked for the application date.

How should annual cash flow and payback be calculated?

Build one row per year with electricity value, operating costs, finance payments, repairs, replacements, assistance, taxes where relevant, and the net cash flow. Simple payback is the point when cumulative net cash flow recovers the initial outflow, but it does not capture time value, later costs, or risk.

Use these formula structures:

• annual net operating value = avoided import value + export value - operating costs - repair and replacement costs
• project net cash flow = operating value - project payments - finance payments + confirmed assistance and other supported inflows
• cumulative cash flow in year n = sum of project net cash flow from start through year n

For discounted cash flow, NPV, IRR, tax treatment, depreciation, business use, or loan comparison, use a qualified financial and tax reviewer. The solar inverter TCO guide is narrower and should not replace the whole-project worksheet.

Do not show a payback result without the inputs and calculation file. A result rounded to one number can conceal tariff escalation, generation decline, downtime, replacement, finance, or export assumptions that drive the answer.

Which sensitivity cases should be tested?

Test the assumptions that can change the decision: generation, self-consumption, export credit, avoided tariff, project delay, installed price, finance cost, operating cost, downtime, replacement timing, ownership horizon, and assistance. Change one variable at a time first, then run combined conservative and favourable scenarios without assigning invented probabilities.

At minimum, compare:

Report which input moves the result most. If a benefit exists only in the favourable case, the decision should be described that way rather than presented as a typical outcome.

When may rooftop solar not be the right next step?

Pause when roof rights or structural suitability are unresolved, shading is material and unmodelled, the connection or export route is unclear, the quote hides scope, finance is unaffordable, ownership is too short for the conservative case, or the design cannot meet the household’s actual backup or operating need. Resolve the blocker first.

Other options may include reducing avoidable consumption, correcting billing or electrical issues, improving roof access, comparing finance, choosing a smaller design, separating battery backup from the PV decision, or waiting for a property or load change. Not yet is different from never.

Solar can also be valuable for reasons not fully captured by simple payback, such as defined backup or an organisational energy objective. Label that value rather than forcing it into an invented rupee figure.

What is the final rooftop-solar decision worksheet?

A defensible worksheet names every source, observation date, unit, assumption, formula, scenario, unresolved approval, responsible reviewer, and update trigger. It compares the solar option with the realistic alternative over the same horizon and separates measured inputs, current documents, quoted values, calculated outputs, estimates, and non-financial preferences.

Before deciding:

1. Verify bill and tariff inputs line by line.
2. Confirm roof, shading, structure and ownership evidence.
3. Obtain an exact-model design and site-specific generation report.
4. Estimate self-consumption and export from a time-aligned load basis.
5. Audit the quote for all inclusions, exclusions, taxes and change rules.
6. Record current grid, metering and assistance requirements.
7. Add finance, operating, service and supported replacement scenarios.
8. Compute annual and cumulative cash flow with a script or spreadsheet.
9. Run sensitivity cases and document the decision threshold.
10. Obtain technical, policy, financial and tax review where applicable.

Use the residential solution route to request a project-specific Qbits discussion. Bring the worksheet and ask the installer to replace assumptions with written evidence rather than offering a universal saving or payback.