Solar Calculator for Chennai
FREE · NO SIGNUPEnter your electricity bill and see the system size you need, the subsidy you qualify for, and what you would save. No signup, no email wall, no phone number required.
Step 1 · What you spend
Estimated from your bi-monthly bill using the TNERC LT-IA slabs. and takes ten seconds to find on the bill.
Step 2 · What kind of property
Step 3 · Optional, sharpens the answer
Recommended system size
2 kW
Sized against an estimated 3,678 units a year, on Tamil Nadu's domestic slabs.
Per day
9 units
Per month
273 units
Per year
3,280 units
Roof needed
100 sq ft
Subsidy
₹60,000
PM Surya Ghar
Cost, market range
₹1.28L to ₹1.40L
After subsidy: ₹68,000 to ₹80,000
Saves per year
₹18,017
Capped at what you actually consume
Payback
3.8 to 4.4 yrs
₹4.50L over 25 years, simplified
These are estimates based on Chennai averages and current market rates, not a Blues Renewables quotation. Your actual price depends on your roof, your connection and your sanctioned load. Send us your bill and we will give you an exact figure.
Get an exact figure for my roof →Method
How we calculate your solar savings
This calculator estimates your system size by converting your electricity bill into annual consumption, then dividing by what a rooftop system generates here — about 1,640 units per kW per year, or 4.5 units per kW per day. It then applies the PM Surya Ghar subsidy slabs, current market installation rates, and Tamil Nadu's telescopic tariff structure to estimate savings and payback. For business and factory connections it uses commercial slab rates instead, and does not price the system.
What makes this different from a generic solar calculator
It uses Tamil Nadu's actual tariff structure
Most calculators divide your bill by a flat rate per unit. Tamil Nadu's domestic tariff is telescopic with a free-unit allowance, so a flat divisor produces a misleading answer.
It accounts for the 500-unit threshold
Households above 500 units per bi-monthly cycle receive fewer free units and pay higher slab rates, so their savings per unit generated are higher. The calculator flags this.
It caps savings at your consumption
Generating more than you use does not save more, because surplus credit still unused on 31 March lapses unpaid. Calculators that ignore this overstate savings on larger systems.
It uses one generation figure, stated openly
4.5 units per kW per day, or about 1,640 a year, which is the figure every page on this site is built on. Your actual output varies with shading, orientation and soiling, which is what the survey establishes.
Honest limits
Why your actual quote will differ
A calculator works from averages. Your actual system size and price depend on your usable shade-free roof area, your sanctioned load, whether your connection is single or three phase, your roof type and access, and how far you are from the coast. Those are established by a site survey, not by a form.
| What changes the answer | Why |
|---|---|
| Usable roof area | After water tanks, headrooms, parapet walls and shading, which is often much less than total terrace size |
| Sanctioned load | System capacity cannot exceed it. The most common blocker |
| Phase | Systems above 4 kW usually require a three-phase conversion |
| Roof type | Sloped and tiled roofs cost more to mount than flat terraces |
| Distance from the coast | Coastal properties need salt mist certified modules and corrosion-resistant structures |
| Your consumption pattern | Not just its total, since daytime consumption is worth more than evening consumption |
The calculator gets you to a realistic ballpark. The survey gets you to a number you can rely on.
Next
What to do with the result
If the numbers look good
Send us your last bill and we will survey the roof, check your connection and sanctioned load, and come back with an itemised quotation and the exact subsidy figure.
If the payback looks long
It may genuinely be. Households consuming within Tamil Nadu's free-unit allowance have relatively little billed consumption for solar to displace. We will tell you that at the survey rather than after installation.
If you want to understand the numbers better
The calculator used averages
Get an exact figure for your roof
We will use your roof. Send us your area and your last bill and we will come back with your actual system size, an itemised price and the subsidy applied.
Faster route: WhatsApp a photo of your latest EB bill to 98841 07170. One photo tells us more than a form does.
Common questions
Solar calculator, common questions
How accurate is this solar calculator?
It gives a realistic ballpark based on Chennai averages, current market rates and Tamil Nadu's tariff structure. It cannot know your usable shade-free roof area, your sanctioned load, whether your connection is single or three phase, or your roof type, all of which affect the final figure. A site survey establishes those.
How do I know what system size I need?
Divide your annual electricity consumption in units by roughly 1,640, which is what one kW generates in a year in Chennai at 4.5 units a day. A household consuming 4,900 units a year needs approximately 3 kW. The calculator does this for you and adjusts for roof area if you provide it.
How much does 1 kW of solar generate in Chennai?
About 4.5 units per kW a day, or roughly 1,640 units a year, based on approximately 5.3 peak sun hours daily. Chennai's generation per kW is higher than most of northern India. Output peaks in the clear hot months and dips through the northeast monsoon.
Does a bigger system save more money?
Only up to the point where it matches your consumption. Beyond that, surplus is exported and any credit still unused on 31 March lapses unpaid, so the extra capacity does not pay back the way self-consumed capacity does. The calculator caps estimated savings at your consumption for this reason.
Why is my payback longer than I expected?
Usually because your consumption sits within Tamil Nadu's free-unit allowance, so there is relatively little billed consumption for solar to displace. Households consuming above 500 units per bi-monthly cycle see much faster returns, because they receive fewer free units and pay higher slab rates on a large volume.
Does the calculator include the subsidy?
Yes. It applies the PM Surya Ghar slabs of ₹30,000 at 1 kW, ₹60,000 at 2 kW and ₹78,000 for 3 kW and above, for residential systems. Apartments are flagged toward the society route, and businesses toward accelerated depreciation, since neither receives the household subsidy.
Is the price shown a quotation?
No. It is a market range for Chennai, not a Blues Renewables quotation. Your actual price depends on your roof, connection, structure and location, which is why we quote after a survey rather than from a form.
Do I have to give my phone number to see the results?
No. The calculator is free and shows results immediately without any signup. The contact form is optional and only there if you want an exact quotation.