3 kW is the most popular rooftop solar size for Chennai homes, and for good reason. It earns the maximum ₹78,000 PM Surya Ghar subsidy, fits on most terraces, and covers the usage of a typical 2–3 BHK home with a couple of air conditioners. This guide answers the questions homeowners ask most: how many units does a 3 kW system produce, what does it cost, and how much will it really save?
- Units per day: about 11.5–13.5 units on average; up to ~15 on clear summer days, down to ~10–11 in the northeast monsoon.
- Units per month: about 350–410 units, or 700–820 units per bi-monthly bill.
- Units per year: about 4,200–4,900 units.
- Price: about ₹2.1–2.3 lakh before subsidy, ₹1.35–1.5 lakh after the ₹78,000 subsidy.
- Savings: about ₹3,000 a month for a home using 900 units per bi-monthly bill; payback in roughly 4 years.
- Roof space: about 250–300 sq ft of shade-free terrace.
How many units does a 3 kW solar system produce in Chennai?
Chennai gets strong sunshine for most of the year. A well-installed, south-facing, shade-free 3 kW system produces roughly:
| Period | Units from 3 kW | Per 1 kW |
|---|---|---|
| Per day (average) | 11.5–13.5 | 3.8–4.5 |
| Per month | 350–410 | 115–137 |
| Per TNPDCL bill (2 months) | 700–820 | 230–275 |
| Per year | 4,200–4,900 | 1,400–1,640 |
One unit is one kWh. The range reflects real-world differences: panel quality, tilt and direction, shading from tanks or neighbouring buildings, dust, heat and inverter efficiency. A good installer should give you a written generation estimate for your specific roof.
Month-by-month and seasonal generation in Chennai
Output follows the sun and the rain. Chennai's pattern differs from most of India because our heaviest rain comes with the northeast monsoon (October–December), not in July–August.
| Season | Months | Approx. units per day (3 kW) | Why |
|---|---|---|---|
| Summer | March–June | 13.5–15 | Long, clear days. Highest output, though peak heat trims panel efficiency a little. |
| Southwest monsoon | July–September | 12–13 | Chennai gets relatively little rain in this season, so output stays good. |
| Northeast monsoon | October–December | 10–11 | Cloud cover and heavy rain days. Lowest output of the year. |
| Winter | January–February | 12–13 | Clear skies return; cooler panels work efficiently. |
Under net metering, surplus units from sunny months are credited and carried forward, which helps balance the lower monsoon months. Read more about TANGEDCO net-metering rules.
What can a 3 kW solar system run?
On an average day, 12 units can cover roughly this daily usage in a 3 BHK home:
| Appliance | Typical daily use | Approx. units |
|---|---|---|
| 1.5-ton inverter AC | 6 hours | 5–6 |
| Refrigerator (double door) | 24 hours | 1–1.5 |
| 4 ceiling fans | 10 hours | 2–3 |
| LED lights, TV, router, laptop | Evening | 1–1.5 |
| Water pump, washing machine, mixer | Short use | 1 |
| Total | ≈ 11–13 |
An on-grid system does not need to power these "live". It feeds the grid by day and the net meter balances what you use at night. Note that an on-grid system shuts down during a power cut for safety; see on-grid vs hybrid for Chennai houses if outages are frequent where you live.
3 kW solar system price in Chennai (2026)
| Approx. amount | |
|---|---|
| System price (on-grid, DCR panels, installed) | ₹2.1–2.3 lakh |
| PM Surya Ghar central subsidy | − ₹78,000 (₹30,000 per kW for the first 2 kW + ₹18,000 for the third) |
| Your net cost | ₹1.35–1.5 lakh |
These indicative figures are based on published Chennai prices in 2026. An elevated structure, premium TOPCon panels, a hybrid inverter or long cable runs (common in flats) add to the cost. Compare all sizes on our solar panel price list for Chennai and check your subsidy with the Chennai solar subsidy calculator.
Paying in EMIs? A PM Surya Ghar bank loan for a 3 kW system works out to roughly ₹2,300–3,000 a month over 7–10 years. See our guide to the solar loan in Chennai.
What's inside a 3 kW solar system
| Component | Typical specification |
|---|---|
| Solar panels | 5–6 DCR panels of 540–600 W (mono PERC or TOPCon), from an ALMM-listed maker |
| Inverter | 3 kW single-phase on-grid string inverter (hybrid if you want battery backup) |
| Mounting structure | Hot-dip galvanised steel, cyclone-rated; low or elevated |
| Electrical | DC and AC cables, AC and DC distribution boxes, surge protection |
| Safety | Earthing and lightning arrester |
| Metering | Bi-directional net meter installed by TNPDCL |
| Monitoring | Wi-Fi or app-based generation monitoring |
Using DCR panels and a registered PM Surya Ghar vendor is essential: without them, you lose the subsidy.
How much does a 3 kW system save under the 2026 TNPDCL tariff?
Tamil Nadu's domestic tariff is billed every two months and has an important threshold in 2026:
- Up to 500 units per bi-monthly bill: the first 200 units are free (from May 2026).
- Above 500 units: only the first 100 units are free, and every unit above 500 is charged at higher slab rates, rising to roughly ₹12 a unit.
That threshold is why solar works so well for Chennai homes with higher bills. A 3 kW system produces 700–820 units per bill, which can pull a high-consumption home's net usage below 500 units, back into the 200-free-units bracket, and remove its most expensive units first.
Worked examples (one bi-monthly bill, 3 kW producing ~750 units)
| Your usage per bill | Approx. bill without solar | Net usage with 3 kW | Approx. bill with solar | Approx. saving per month |
|---|---|---|---|---|
| 600 units | ₹3,030 | 0 (surplus credited) | ≈ ₹0 | ≈ ₹1,500 |
| 700 units | ₹4,025 | 0 (surplus credited) | ≈ ₹0 | ≈ ₹2,000 |
| 900 units | ₹6,125 | 150 | ≈ ₹0 | ≈ ₹3,050 |
| 1,200 units | ₹9,660 | 450 | ≈ ₹1,320 | ≈ ₹4,170 |
Estimates use the 2025-26 telescopic energy rates (about ₹4.95–₹12.15 a unit) with the 2026 free-unit rules, and exclude electricity duty and any surplus-export credit. Tariffs are revised periodically; check your latest bill for current rates.
Payback period
| Usage per bill | Approx. yearly saving | Payback on ₹1.45 lakh net cost |
|---|---|---|
| 600 units | ≈ ₹18,000 | ≈ 8 years |
| 700 units | ≈ ₹24,000 | ≈ 6 years |
| 900 units | ≈ ₹36,700 | ≈ 4 years |
| 1,200 units | ≈ ₹50,000 | ≈ 3 years |
After payback, the savings continue for the rest of the system's 25-year panel life. For more bill examples, read how much solar saves a Chennai home.
Is 3 kW the right size for your home?
| Your usage per bi-monthly bill | Best size | Why |
|---|---|---|
| Up to 500 units | 1–2 kW | You already get 200 free units. A 3 kW system would mostly export surplus at a low credit, so payback is slow. |
| 500–900 units | 3 kW | Brings net usage under 500 and removes the costliest slab units. Best value. |
| 900–1,200 units | 3–4 kW | 3 kW already saves heavily; 4 kW clears more of the bill if roof space allows. |
| Above 1,200 units | 4–5 kW | Larger homes, several ACs or an EV. Compare 3 kW vs 5 kW. |
Get a closer figure from your own bill with the solar system size calculator. Live in a flat? See solar for a 3 BHK flat in Chennai.
How to get the most units from a 3 kW system
- Face panels south at a tilt of roughly 10–15° for Chennai's latitude.
- Avoid shade from water tanks, staircase rooms, trees and neighbouring buildings. Even partial shade on one panel can drag down the whole string.
- Clean panels every 2–3 weeks with plain water, more often near the coast where salt and dust settle.
- Choose heat-tolerant panels with a low temperature coefficient; TOPCon generally loses less output in Chennai's heat.
- Use a cyclone-rated, hot-dip galvanised structure so the system survives the northeast monsoon.
- Watch the monitoring app: a sudden drop in daily units usually means dirt, shade or an inverter fault.
Frequently asked questions
How many units does a 3 kW solar system produce per day in Chennai?
About 11.5–13.5 units a day on average. Clear summer days can reach around 15 units, while cloudy northeast-monsoon days drop to about 10–11.
How many units does a 3 kW system produce per month?
Roughly 350–410 units a month, or 700–820 units per bi-monthly TNPDCL bill, and about 4,200–4,900 units a year.
What is the price of a 3 kW solar system in Chennai after subsidy?
About ₹1.35–1.5 lakh after the ₹78,000 PM Surya Ghar subsidy, on a system price of roughly ₹2.1–2.3 lakh, based on indicative 2026 Chennai prices.
Can a 3 kW solar system run an AC?
Yes. Over a day, a 3 kW system produces enough units to cover a 1.5-ton inverter AC for around 6 hours plus a fridge, fans and lights. On an on-grid system the net meter balances daytime generation against night-time use.
How much does a 3 kW system save per month in Chennai?
It depends on your usage. A home using about 900 units per bi-monthly bill can save roughly ₹3,000 a month, because solar removes the costliest units and can bring usage under the 500-unit threshold where 200 units are free.
How much roof space does a 3 kW solar system need?
About 250–300 sq ft of shade-free terrace, typically for 5–6 panels of 540–600 W.
Does a 3 kW solar system work during the monsoon?
Yes, at reduced output. Generation drops to around 10–11 units a day during the northeast monsoon, and surplus credited in sunny months under net metering helps balance it.
Is 3 kW enough for a 3 BHK house?
For most 3 BHK homes with two ACs, using about 500–900 units per bi-monthly bill, 3 kW is the right size. Homes with three or more ACs or an EV may need 4–5 kW.
Get a 3 kW solar quote for your home
Arka Solar Energy, a solar company in Chennai, sizes your system from your actual EB bills, gives a written generation estimate for your roof, and handles the PM Surya Ghar subsidy and TNPDCL net metering. Send your last EB bill on WhatsApp for a free estimate.
Generation figures are typical ranges for well-installed systems in Chennai and vary with roof, orientation, shading and equipment. Prices are indicative 2026 Chennai figures. Savings use the 2025-26 TNPDCL energy rates with the 2026 free-unit rules; confirm current tariffs on your bill. Comparing installers? See the best residential solar companies in Chennai.