Housing Society Solar Calculator

Size a rooftop system for your society's common areas, apply the ₹18,000 a kW PM Surya Ghar subsidy and split the cost and saving per flat.

Updated 9 October 2026 · By Niraj Kumar · 1 source

Your society

Solar for

My home

Housing society

Flats or houses in the society

The subsidy counts at most 3 kW a house, up to 500 kW. Costs and savings are split across them.

State and electricity company

From your bill, enter

Amount (₹)

Units (kWh)

Average monthly common-area bill

₹

₹100₹5L

About 1,963 units a month on the MSEDCL tariff. Use a year's average if your bill swings with the seasons.

Roof type

RCC flat roof

RCC, elevated structure

Metal sheet roof

Fine-tune

System size

Sized to cover a year of your consumption, at 5.4 peak sun hours a day in Maharashtra.

Usable shadow-free roof area (optional)

sq ft

About 100 sq ft per kW. Leave at 0 for no limit.

Installed cost per kW, GST included

₹

Typical for an on-grid system from an empanelled vendor. Replace it with your quote.

Yearly rise in electricity prices

0%15%

Indian residential tariffs have historically risen 4-7% a year.

Panel output lost each year

0%2%

Monocrystalline panels typically lose about 0.5% a year.

How you pay

Upfront

Solar loan

Pays for itself in1 yearthen ₹2.13 Cr ahead after 25 years

A 15.5 kW system makes about 1,960 units a month, 100% of the common areas' use. The common-area bill drops from ₹40,000 to about ₹168 in year one.

Installed cost: ₹7,75,000
PM Surya Ghar society subsidy: − ₹2,79,000; ₹18,000 a kW on 15.5 kW
Net cost to the society: ₹4,96,000
Per flat: ₹12,400; upfront, then about ₹11,948 saved in year one
Saving in year one: ₹4,77,933
Return (IRR): 101.1% a year; over 25 years, before tax
CO₂ avoided: 399 tonnes; over 25 years

Subsidy36%

You pay64%
Central subsidy36%

Your money over 25 yearsStill to recoverAhead

Year-by-year cash flowShow

Year	Units made	Bills without solar	Bills with solar	Upkeep and EMIs	Running total
1	23,524	₹4,79,950	₹2,017	₹0	-₹18,066
2	23,406	₹5,03,948	₹2,914	₹0	₹4,82,967
3	23,289	₹5,29,145	₹3,892	₹0	₹10,08,221
4	23,173	₹5,55,602	₹4,956	₹0	₹15,58,867
5	23,057	₹5,83,383	₹6,112	₹0	₹21,36,138
6	22,942	₹6,12,552	₹7,367	₹7,750	₹27,33,573
7	22,827	₹6,43,179	₹8,726	₹7,750	₹33,60,276
8	22,713	₹6,75,338	₹10,198	₹7,750	₹40,17,665
9	22,599	₹7,09,105	₹11,791	₹7,750	₹47,07,230
10	22,486	₹7,44,560	₹13,511	₹7,750	₹54,30,530
11	22,374	₹7,81,788	₹15,367	₹7,750	₹61,89,201
12	22,262	₹8,20,878	₹18,646	₹1,16,250	₹68,75,182
13	22,151	₹8,61,922	₹22,454	₹7,750	₹77,06,900
14	22,040	₹9,05,018	₹26,581	₹7,750	₹85,77,588
15	21,930	₹9,50,269	₹31,048	₹7,750	₹94,89,058
16	21,820	₹9,97,782	₹35,879	₹7,750	₹1,04,43,211
17	21,711	₹10,47,671	₹41,099	₹7,750	₹1,14,42,034
18	21,602	₹11,00,055	₹46,733	₹7,750	₹1,24,87,606
19	21,494	₹11,55,058	₹52,808	₹7,750	₹1,35,82,105
20	21,387	₹12,12,811	₹59,355	₹7,750	₹1,47,27,811
21	21,280	₹12,73,451	₹66,404	₹7,750	₹1,59,27,108
22	21,174	₹13,37,124	₹73,988	₹7,750	₹1,71,82,494
23	21,068	₹14,03,980	₹82,142	₹7,750	₹1,84,96,581
24	20,962	₹14,74,179	₹90,903	₹7,750	₹1,98,72,107
25	20,858	₹15,47,888	₹1,00,310	₹7,750	₹2,13,11,934

How is a housing society's solar payback worked out?

PM Surya Ghar pays a housing society or RWA ₹18,000 per kW for common facilities, EV charging included, on up to 500 kW and no more than 3 kW for each house: up to ₹90,00,000 in all.

Saving₍y₎ = [Bill(U) − Bill(U − G₍y₎/12)] × 12 × (1 + e)^(y−1),  G₍y₎ = kW × H × 365 × PR × (1 − d)^(y−1)

This page uses the same method as the Solar ROI Calculator India, which explains each term and assumption in full.

Worked example

A 60-flat society in Pune on MSEDCL whose lifts, pumps and common lighting run up a ₹40,000 monthly bill, with a flat RCC terrace.

1Working the bill back through MSEDCL's residential slabs, which also cover a housing society's common areas, gives about 1,963 units a month
215.5 kW covers that use; at ₹50,000 a kW it costs ₹7,75,000
3PM Surya Ghar pays ₹18,000 a kW for common facilities, ₹2,79,000 here, leaving ₹4,96,000: ₹8,267 a flat
4The first year saves ₹4,77,933 on the common bill, ₹7,966 a flat

The society recovers the cost in about 1.0 years and is about ₹2,13,11,934 ahead over 25 years.

Frequently asked questions

How much subsidy does a housing society get under PM Surya Ghar?

₹18,000 for every kW installed for common facilities, up to 500 kW. The size that qualifies is also capped at 3 kW a house, so a 20-flat society can claim on up to 60 kW. State top-ups such as Delhi's or UP's are for individual homes and are left out here.

Can flats in a society claim the home subsidy as well?

Each household can claim the individual PM Surya Ghar subsidy once, for a system on its own connection, while the society claims separately for its common-area connection. In most apartment buildings the terrace only has room for the common-area system.

Which tariff does a society's common-area bill use?

It depends on the state. Maharashtra, Delhi and several others bill a residential society's common facilities on the residential tariff, which this calculator uses. Where your DISCOM charges a separate or commercial rate, replace the bill with units from the bill and the saving still follows your actual rate. Free units and bill waivers for homes are left out.

Who decides to install solar in a housing society?

Usually the general body, by resolution, since the terrace and the common-area connection belong to the society. The society then applies on the PM Surya Ghar portal under the GHS/RWA category with its common-area consumer number, and the subsidy is paid to the society's account after commissioning.

Sources

MNRE, PM Surya Ghar: Muft Bijli Yojana (central subsidy) · checked 9 October 2026