4kW Solar System: Price, Units Per Day & Is It Enough? (TN 2026)

Short answer: a 4kW solar system makes about 16-20 units a day in Tamil Nadu (about 960-1,200 units per two-month TNEB bill). It costs about ₹2.4-2.7 lakh installed in 2026, or about ₹1.4-1.7 lakh after the up to ₹1 lakh subsidy for an eligible home. It suits homes using roughly 800-1,100 units every two months, typically a 3BHK with one or two ACs used moderately.

Prices are market averages as of October 2026, not our quotes. Your exact price comes after a free site visit.

4kW at a Glance

The math: 4 kW × about 4.1 units per kW per day ≈ 16.4 units on an average day, rising to 20 on clear summer days.

Is 4kW Enough for Your Home?

Bills are approximate using TNEB domestic slabs. Check yours with the free TNEB EB bill calculator or the solar savings calculator.

4kW vs 3kW vs 5kW

Because the subsidy stops growing at 3kW, every kW above 3kW is paid fully by you. That is why 4kW makes sense only when your bill really needs it. If you are between sizes, a correctly sized 3kW plus energy-saving habits can beat an oversized system. Compare: 3kW system page, 5kW system page, 3kW vs 5kW.

What Can a 4kW System Run?

A 4kW system's 16-20 units a day can cover a typical day's load like this:

With net metering, units you do not use in the day go to the grid and are credited, so evening AC use is covered by daytime export. See how many units an AC uses.

Single Phase or Three Phase?

Many 4kW systems work on a single-phase connection with a 4-5kW single-phase inverter, as long as your sanctioned load supports it. If your load is low, TNEB may ask for a load increase first. Larger systems usually move to three phase. Details: single phase to 3-phase upgrade for solar.

Payback for a 4kW System

For a home using about 1,000 units every two months (a bill of about ₹6,700), a 4kW system can save roughly ₹36,000-40,000 a year. With a net cost of about ₹1.4-1.7 lakh after subsidy, payback is about 3.5-4.5 years, followed by 20+ years of low bills. Full method: solar payback after ₹1 lakh subsidy.

4kW On-Grid or Hybrid?

On-grid gives the lowest price and fastest payback, and suits most homes. Choose a hybrid 4kW system with a battery only if power cuts are long or frequent in your area, or someone at home needs uninterrupted power. A battery adds roughly ₹1-1.6 lakh for a 5kWh lithium pack and is not subsidised. See solar with battery backup price.

3 Common 4kW Sizing Mistakes

1. Sizing from one summer bill. Use the average of your last 6 bills, or you may oversize and pay for units you never use.
2. Ignoring a planned AC or EV. If a second AC or an electric scooter is coming, plan for it now; adding panels later costs more per watt.
3. Not checking roof space first. 4kW needs about 330-400 sq ft of shade-free area. Water tanks and coconut trees can make a 3kW layout the practical maximum. Read how much roof space solar needs.

4kW Buying Checklist

1. DCR panels in writing, or you lose the subsidy.
2. Inverter sized to match: a 4-5kW on-grid inverter, BIS registered.
3. Hot-dip galvanized structure if you live near the coast.
4. Three earthing pits and a lightning arrester.
5. Registered PM Surya Ghar vendor, with an itemised quote. See how to compare solar quotations.

Not sure you qualify? Check in 30 seconds with the subsidy eligibility checker.

Get the Right Size, Not the Biggest

Send us your last two TNEB bills on WhatsApp and we will tell you honestly whether 3kW, 4kW or 5kW suits your home, with a written quote after a free site visit. Registered PM Surya Ghar vendor serving Cuddalore, Puducherry, Neyveli and nearby towns. Call or WhatsApp +91 7904369094.