Key Summary
Most homeowners start thinking about solar with the same two questions: what size system do I actually need, and what will it cost me? The honest answer is usually “it depends,” and until now getting a real number meant waiting for an installer to call you back. Alpex’s solar rooftop calculator skips that wait. Enter your electricity bill and location, and you get a personalised estimate of your system size, installation cost, subsidy, and monthly savings in under a minute, before you talk to anyone.
What Is a Solar Rooftop Calculator?
A solar rooftop calculator is an online tool that turns a few basic details, mainly your monthly electricity bill and where you live, into an estimate of the solar system that would suit your home. It works out the recommended capacity in kilowatts (kW), the likely installation cost, the government subsidy you qualify for, and how much you could save each month.
One thing worth being upfront about: this is an estimate, not a final design. Your roof’s actual shading, orientation, and structure can only be confirmed by a site visit. Think of the calculator as a solid starting point that saves you a few conversations, not the last word on your project.
How to Use the Calculator — Step by Step
Using it takes less time than reading this paragraph.
What the Calculator Shows You
Once you submit your details, the calculator returns a set of results that map directly to the decisions you’ll eventually make with an installer:
Because generation depends on your state’s average sun-hours and how much shading your roof gets, two homes with identical bills in different cities can get slightly different recommendations. That’s expected, not an error.
How the Estimate Is Calculated
The logic behind the numbers is fairly simple. Your monthly bill is first converted into an estimated consumption figure. That figure, combined with the average sun-hours for your state, gives a recommended system size in kW. From there, the calculator applies current per-kW installation pricing to arrive at a cost estimate, and applies the latest PM Surya Ghar subsidy slabs to show what you’d pay after government support.
This is broadly the same approach used by the official government calculator and most other tools in this space. There’s no hidden formula here, which is really the point: a transparent method is easier to trust than a black box that just spits out a number.
Why Use Alpex’s Calculator
The estimates you see here are built on Alpex’s own panel specifications, which are ALMM (Approved List of Models and Manufacturers), BIS (Bureau of Indian Standards), and DCR (Domestic Content Requirement) listed, rather than generic industry averages pulled from nowhere in particular. That means the numbers reflect equipment you could actually end up installing, not a hypothetical average panel.
If the estimate looks promising, the natural next step is a free site survey or a quote request. There’s no obligation attached to using the calculator itself; it’s simply meant to give you a realistic starting number before you decide whether to go further.
Government Subsidy on Rooftop Solar
Under the PM Surya Ghar Muft Bijli Yojana, the central government provides a capacity-based subsidy for residential rooftop solar. As things currently stand, you receive ₹30,000 per kW for the first 2 kW of capacity, and an additional ₹18,000 for the third kW, which brings the subsidy to a maximum of ₹78,000 for systems of 3 kW or larger. Systems above 3 kW don’t receive extra subsidy beyond this cap, though some states add their own top-up on top of the central amount (see Maharashtra and Gujarat).
If you want to see the official version of this tool, the government runs its own National Portal for Rooftop Solar Calculator at pmsuryaghar.gov.in, and it’s worth a look for cross-checking your numbers. For a full breakdown of eligibility, documents, and the application process, Alpex’s PM Surya Ghar guide covers it in detail.
Ready to See Your Numbers?
In under a minute, the calculator gives you a personalised starting point: system size, cost, subsidy, and savings, all in one place. From there, the next step is entirely up to you. Try the calculator above, or if you’d rather skip straight to an exact number, request a free site survey and get a quote built around your actual roof.
