1 kW or 2 kW Solar for a Small Home: What It Costs and When It Is Not Worth It

Published August 29, 2025 · Updated October 6, 2026 · Reviewed by Karthikeyan E

A small home in Coimbatore has two sensible options: a 1 kW system at Rs 51,400 after subsidy or a 2 kW at Rs 85,000. Which one, and whether either is worth it, depends on one number: the units on your two-month EB bill. Below 400 units neither pays back in a reasonable time. We would rather say that here than on a site visit.

The short answer

	1 kW	2 kW
Our price	Rs 86,400	Rs 1,55,000
Subsidy (central + Tamil Nadu)	Rs 30,000 + Rs 5,000	Rs 60,000 + Rs 10,000
You pay	Rs 51,400	Rs 85,000
Shadow-free roof needed	About 100 sq ft	About 130 to 150 sq ft
Panels	2 of 540 to 555 W	4 of 540 to 555 W
Units made in two months	About 330	About 660
Network charge per bill	About Rs 93	About Rs 185
Suits a home using	400 to 500 units in two months	600 units and above

Prices are our current quotes within 50 km of the city and include the panels, inverter, structure, wiring, earthing and the net-meter paperwork. The 1 kW system page and the 2 kW system page list what is in each.

First, find your units

Take the last two or three EB bills and read the units, not the rupees. Homes are billed once in two months. If the figure is 500 or less, the first 200 units are free since May 2026; above 500 only the first 100 are free and the rates climb slab by slab. That rule decides everything below, and it is explained in our 2026 tariff table.

The payback table

Bills are energy charges for two months at 2026 rates. The "after" figure is the bill on the units you still draw from the grid, plus the network charge. A 1 kW system makes about 330 units in two months here, a 2 kW about 660.

Units in two months	Bill now	1 kW: bill after	1 kW: payback	2 kW: bill after	2 kW: payback
200	Rs 0	Rs 93	Never	Rs 185	Never
300	Rs 470	Rs 93	About 23 years	Rs 185	About 50 years
400	Rs 940	Rs 93	About 10 years	Rs 185	About 19 years
500	Rs 1,570	Rs 93	About 6 years	Rs 185	About 10 years
600	Rs 2,880	Rs 422	About 3.5 years	Rs 185	About 5 years
700	Rs 3,825	Rs 892	About 3 years	Rs 185	About 4 years
800	Rs 4,770	Rs 1,474	About 2.6 years	Rs 185	About 3 years

Three things stand out. Under 400 units the system costs more than it saves. Between 400 and 500 units a 1 kW works and a 2 kW over-produces. From 600 units the 2 kW pays back in about five years, and the 3 kW system becomes the one to compare it with.

Why under 400 units does not work

Two rules pull against a small system. The first 200 units are already free, so panels that cover them save nothing. The units above that are charged at Rs 4.70, the lowest slab, so each unit the roof replaces saves only Rs 4.70. And the network charge is paid on every unit the system makes, whether you needed it or not. A home on 300 units saves Rs 377 a bill with a 1 kW system; the system costs Rs 51,400. That is 23 years.

1 kW: who it suits

A home that uses 400 to 500 units in two months, with about 100 sq ft of roof clear of shade from 10 am to 3 pm. Two panels of 540 to 555 W and a small inverter. It brings the bill to the network charge and the payback is six to ten years. It does not run anything during a power cut; no grid-tied system does.

2 kW: who it suits

A home at 600 units and above, with 130 to 150 sq ft of clear roof. Four panels. From 600 units it wipes the energy charge; from 800 units the payback is about three years. Below 600 units it makes more than you use, and under net metering the unused credit is cancelled on 31 March every year. Oversizing is the most common mistake we see on small homes. The rule is in our guide to how exported units are credited.

What you still pay after

Item	What to expect
Network charge	20% of Rs 1.53 on every unit the system makes. About Rs 93 a bill for 1 kW, Rs 185 for 2 kW.
Net-meter registration	Rs 500, once, with the application to TNPDCL.
Fixed charge	None. The domestic tariff has no fixed charge.
Cleaning	A wash every few weeks in dusty areas. Two or four panels take ten minutes.

Grid-tied, off-grid or hybrid for a small home

Grid-tied is the default and the only type the subsidy is calculated on. Off-grid means no connection to TNPDCL and a battery bank sized for the whole house, which is a farm or remote-site answer, not a town-home one. Hybrid keeps the grid and adds a battery for power cuts; the battery is paid by you in full. The three are described on our services page. If you live in a flat with a shared roof, read what applies to apartments first.

To run the sums on your own units, use the calculator. The subsidy steps are on the rooftop subsidy page.

Questions people ask

Can I start with 1 kW and add a second kilowatt later?

Yes, if the inverter and the net-meter sanction are sized for it from the start. Tell the installer at the first visit that you plan to expand. Adding later means a fresh application for the extra capacity.

Is the subsidy different for a 1 kW system?

The central share is 60% of the benchmark cost for anything up to 2 kW, which works out to Rs 30,000 for 1 kW and Rs 60,000 for 2 kW. Tamil Nadu adds Rs 5,000 and Rs 10,000. Both are paid into your bank account after the net meter is fixed.

Will a 2 kW system make my bill zero?

From about 600 units in two months, yes, apart from the network charge. Below that it makes more than you use, and the surplus credit is wiped on 31 March every year, so you paid for units you never get back.

Does a small home need a battery?

Not for the bill. A grid-tied system without a battery is the cheapest and the only kind the subsidy is calculated on. A battery makes sense only if power cuts in your area last for hours and you must run something through them.

Sources and disclaimer

TNERC Order No. 4 of 2026: domestic tariff payable by consumers. Slab rates, pages 7 to 9.
TNERC Order No. 5 of 2026: 200 free units for bills up to 500 units
TNERC Order No. 8 of 2021: net metering and network charges
PIB: Cabinet approves PM-Surya Ghar: Muft Bijli Yojana, 29 February 2024. The 60% rule up to 2 kW.

Bills and payback were worked out on 6 October 2026 from the orders above and our price list, using 5.5 units per kilowatt per day for Coimbatore. Your roof, shade and usage will move the figures. RK Solar Solutions is an installer, not a government agency.

Not sure which band you are in? Send us your last two EB bills and we will reply with the size, the net price and the payback in writing, or tell you to wait.