Begin with the assumptions
A rooftop solar decision often begins with two questions: “How many panels can I install?” and “How much will I save?”
Both matter. But useful answers depend on the roof, the sunlight available, household electricity use, equipment, and the rules governing the electricity connection.
A better starting question is: What would have to be true for this estimate to work for my home?
This guide explains how to approach that question, where SolarSight fits, and what to verify before moving from an online assessment to an installation.
1. Understand what an initial assessment can tell you
SolarSight is UGAC’s live rooftop solar assessment platform. Its public product page describes a seven-page report covering the rooftop, recommended system, estimated investment, financial scenarios, environmental indicators and next steps. The public assessment begins by locating the rooftop through search, coordinates or a map selection.
Use an assessment to organise your questions and compare assumptions. A proposed system size is something to investigate; a saving estimate is something to examine.
SolarSight’s own disclaimer identifies its results as estimates based on long-term satellite irradiance, published tariffs, module information and supplied roof details. It also calls for a structural assessment before installation. An online result therefore supports the next conversation; it does not establish final roof suitability, subsidy approval or actual performance.
2. Begin with the right roof and the space you can actually use
Check the selected rooftop before continuing. In dense neighbourhoods, an address or nearby landmark may need closer inspection to identify the intended building.
Then distinguish the roof’s total area from the space available for a practical installation. Water tanks, stair enclosures, parapets, access routes and other uses can affect the layout. A roof that appears open at one time of day may also experience shade at another.
Government rooftop-solar guidance highlights roof material, access and shadow analysis as relevant design considerations. A rough area estimate is useful preparation, but the final arrangement needs site-specific checks.
Roof questions to prepare
Before speaking with an installer, prepare these questions:
- Which parts of the roof are genuinely available?
- What must remain accessible for maintenance or other household uses?
- Which nearby objects could cast shadows?
- Does the roof need repair or a structural review?
- Could planned construction change the available space or sunlight?
These are preparation questions, not a claim that every item is a required SolarSight form field.
3. Keep system capacity and electricity generation separate
A system’s capacity and the electricity it produces describe different things.
Kilowatts (kW) describe power. Solar module capacity is also commonly expressed as kilowatt-peak (kWp), referring to rated output under standard test conditions. Kilowatt-hours (kWh) describe energy produced or consumed over time; one kWh is commonly called one electricity “unit”.
A capacity figure does not mean that the system will produce that amount of power continuously.
Read capacity and generation together
When reading an assessment, identify:
- The proposed module capacity and inverter capacity.
- The estimated monthly and annual generation.
- The inputs and losses used to arrive at those estimates.
- Whether the estimate fits the layout the installer is actually proposing.
This distinction makes quotes easier to compare: two proposals with similar capacity can still use different equipment, layouts and generation assumptions.
4. Read generation as a seasonal estimate
Solar output depends on more than the number printed on a panel. Location, orientation, tilt, temperature, shading, dirt, equipment losses and downtime can affect the result.
Historical solar-resource data is useful for planning, but it is not a forecast of a particular future month. The PVWatts technical guidance explains that typical-weather estimates can differ from actual performance and that overlooked shading or soiling can make results optimistic. This supports a general principle about solar modelling; it is not a validation of SolarSight’s calculations or evidence that SolarSight uses PVWatts.
Ask the installer to explain the monthly generation pattern and the treatment of shade, cleaning and equipment performance. If the proposed layout changes, ask whether the generation estimate should change too.
5. Electricity generated and money saved are different calculations
A solar system’s financial value depends on how the household uses electricity and how the applicable billing arrangement treats exports.
Electricity consumed at home can reduce grid purchases. Surplus electricity sent to the grid may receive a different value or treatment. Fixed charges and other bill components also need separate attention.
An illustrative energy-value example
Consider this illustrative arithmetic example, not a SolarSight result, tariff quote or household forecast:
Suppose a system produces 400 kWh in a month. The household uses 100 kWh directly and exports 300 kWh. Assume, purely for explanation, that avoided purchases are worth ₹8/kWh and exports receive ₹3/kWh.
The value would be:
- Direct use: 100 × ₹8 = ₹800.
- Export: 300 × ₹3 = ₹900.
- Combined value: ₹1,700, before other bill effects.
Valuing all 400 kWh at ₹8 would instead produce ₹3,200. The difference comes from the assumptions, even though generation is unchanged.
Check the rules for your own connection
Actual savings must use the relevant tariff and settlement rules. Official Puducherry guidance, for example, describes net metering as offsetting exports against imports subject to conditions; its arrangements should not be assumed to apply unchanged elsewhere.
For your own comparison, collect recent bills, identify the connection category and ask your DISCOM how imports, exports and settlement are handled.
6. Treat subsidy as an eligibility question
PM Surya Ghar: Muft Bijli Yojana supports residential rooftop solar through an official application process. MNRE’s March 2026 statement describes applications and subsidy disbursal through the National Portal. Completing a private solar assessment is not an application to that scheme.
The commonly published general-category central assistance figures are ₹30,000 for 1 kW, ₹60,000 for 2 kW and ₹78,000 for 3 kW or larger systems. These figures are context, not a personalised entitlement: special-category provisions, state support, eligibility and applicable requirements need checking for the actual installation.
Verify the process and equipment requirements
Before committing, verify the current process with the PM Surya Ghar National Portal and your DISCOM. Ask which equipment documents, vendor requirements and commissioning steps apply.
Also distinguish ALMM listing from Domestic Content Requirement compliance. MNRE’s clarification treats these as separate matters; a panel’s appearance in an approved list should not be treated as the whole subsidy check.
7. Look beyond the headline payback period
A payback estimate is only as useful as its assumptions.
When reviewing SolarSight’s financial scenario or an installer’s proposal, ask what is included in the initial cost, how annual benefits are calculated, and which future expenses are allowed for.
Questions behind a payback estimate
Request clarity on:
- Mounting, wiring, protection, installation and any roof-related work.
- Maintenance responsibilities and possible equipment replacement.
- Financing costs, where relevant.
- Tariff escalation and generation degradation assumptions.
- Subsidy timing and what changes if support differs from the estimate.
Ask for a second scenario using less favourable assumptions. This helps reveal whether the decision depends heavily on one optimistic input.
A long cashflow chart describes a scenario. It does not turn future prices, generation or costs into certainties.
8. Discuss backup power explicitly
Reducing an electricity bill and keeping appliances running during an outage are separate requirements.
A standard grid-connected installation should not be assumed to provide backup. BSES’s interconnection documentation states that the photovoltaic system shuts down during a distribution outage unless special transfer and isolation capabilities have been installed.
If backup matters, specify the appliances, required duration and expected operation during a power cut. Ask the installer what configuration meets that need and how it changes the proposal.
9. Turn the assessment into a useful installer brief
The practical value of an assessment is the conversation it enables.
Take the report, relevant electricity bills and a list of roof constraints to the installer. Request a proposal that explains its assumptions in comparable terms.
Five questions before accepting a proposal
Before accepting it, seek clear answers to five questions:
- What roof, shading and structural checks support this layout?
- Which exact modules, inverter and protective components are included?
- How were monthly generation and bill savings calculated?
- Which approvals, metering and scheme requirements apply?
- Who handles maintenance, faults, warranties and handover?
Keep the final quotation, equipment specifications, commissioning records and service terms together. They will help you compare the installed system with what was proposed.
Start with an assessment. Continue with verification.
SolarSight can help structure the early stages of a rooftop solar decision. Its greatest value is in helping a homeowner move from a broad question to a more specific set of inputs, assumptions and next steps.
Explore the SolarSight assessment, read the assumptions behind the result, and use it to prepare a focused installer discussion.
Before choosing a system, which assumption would you most want to verify: usable roof space, generation, bill savings or subsidy eligibility?
Educational information, researched on 21 October 2026. Product descriptions are based on UGAC’s public pages, not independent performance testing. Tariffs, scheme requirements and individual eligibility should be checked before commitment. Final roof suitability and system design require site-specific assessment.