So if you own a 3BHK home in Tamil Nadu or Kerala, your electricity bill is climbing every month, and someone at the office told you to “just go solar.” Simple enough advice but when you actually sit down and try to figure out how many panels you need, how much it costs, and whether the government subsidy covers your home, it gets confusing fast.
Let me cut through that.
I’ve helped hundreds of homeowners in Kerala and Tamil Nadu size their rooftop solar systems. A 3BHK is one of the most common home types we work with. By the end of this, you’ll know exactly what size system you need, what it costs after subsidy, and what to do next.
What Does a Typical 3BHK Home Actually Consume?
Before sizing a solar system, you need to know your home’s real electricity consumption, not a guess.
A standard 3BHK in Tamil Nadu or Kerala typically runs:
| Appliance | Quantity | Approx. Daily Use | Daily Units (kWh) |
| 1.5 ton inverter AC | 1–2 | 6–8 hours | 5–7 kWh |
| Refrigerator | 1 | 24 hours | 1–1.5 kWh |
| Washing machine | 1 | 1 hour | 0.5 kWh |
| LED lights + fans | 8–10 | 6 hours | 0.5 kWh |
| TV, set-top box, misc. | – | 4–5 hours | 0.3–0.5 kWh |
| Water heater / geyser | 1 | 30 min | 0.5–1 kWh |
Total: roughly 8–11 units (kWh) per day, which works out to 240–330 units a month.
If your electricity bill shows 250–350 units a month, that’s your benchmark. That’s the number we size the solar system against.
So How Many kW Solar Does a 3BHK Need?
For a 3BHK home consuming 250–350 units per month in Tamil Nadu or Kerala, a 3kW to 5kW solar system is the right range.
Here’s the simple logic:
- A 1kW solar system generates roughly 4–5 units per day in South India (good sun irradiation)
- A 3kW system gives you 12–15 units/day → 360–450 units/month
- A 5kW system gives you 20–22 units/day → 600–660 units/month
Recommended system size by usage:
| Monthly Consumption | Recommended System | What It Covers |
| 150–200 units | 2kW | Basic 3BHK, no AC |
| 200–300 units | 3kW | 3BHK with 1 AC (moderate use) |
| 300–400 units | 4–5kW | 3BHK with 1–2 ACs, daily use |
| 400+ units | 5kW+ | Heavy usage, EV charging, large family |
Most 3BHK homes in Kerala and Tamil Nadu land comfortably in the 3kW–5kW range. If you run AC regularly through summer, go with 5kW. If AC use is light or you have one unit, 3kW is sufficient.
On-Grid, Off-Grid, or Hybrid – Which Works for a 3BHK?
This is the question most homeowners get stuck on. Here’s the short answer for Tamil Nadu and Kerala:
On-grid solar is the right choice for most 3BHK homes.
Here’s why:
- Your home stays connected to the KSEB or TNEB grid
- Excess solar power goes back to the grid through net metering you earn credits
- No battery needed, so cost stays lower
- Eligible for PM Surya Ghar subsidy (up to ₹78,000 for a 3kW system)
Hybrid solar makes sense if:
- Your area has frequent power cuts (many Kerala and Tamil Nadu rural areas do)
- You want battery backup without going fully off-grid
- You’re planning EV charging at home in the next 2–3 years
Off-grid solar is rarely the right call for a 3BHK in Tamil Nadu or Kerala. It costs significantly more (batteries), and most urban and semi-urban areas here have decent grid supply.
My advice: start with on-grid if your grid is stable, go hybrid if you see 4+ hours of power cut per week.
How Much Roof Space Does a 3BHK Solar System Need?
This is often overlooked. You need to check whether your terrace or rooftop can actually fit the panels.
| System Size | Panels Needed (approx.) | Roof Area Required |
| 2kW | 5–6 panels | 120 sq. ft |
| 3kW | 8–9 panels | 180 sq. ft |
| 4kW | 10–12 panels | 240 sq. ft |
| 5kW | 13–15 panels | 300 sq. ft |
Most 3BHK terraces in Kerala and Tamil Nadu have 400–600 sq. ft of usable roof, so a 5kW system easily fits. Even a 3BHK flat in a gated community typically has 200–300 sq. ft of exclusive terrace access.
Things that reduce usable area: water tanks, staircases, AC outdoor units, shading from neighbouring buildings or trees. Always get a site visit done before you finalise system size.
What Does a 3kW–5kW Solar System Cost in Tamil Nadu and Kerala?
Let’s talk about real numbers. No vague ranges this is what homeowners actually pay in 2026.
3kW solar system:
- Before subsidy: ₹1.6L–₹2.0L
- PM Surya Ghar subsidy: up to ₹78,000
- After subsidy: ₹85,000–₹1.2L
5kW solar system:
- Before subsidy: ₹2.4L–₹3.2L
- PM Surya Ghar subsidy: up to ₹78,000 (capped at 3kW for full subsidy)
- After subsidy: ₹1.7L–₹2.5L
These prices include panels, inverter, mounting structure, wiring, net meter application, and installation. There are no hidden extras when you go through a registered solar company.
Your payback period in Kerala and Tamil Nadu is typically 4–6 years after which you’re generating essentially free electricity for the next 20+ years.
See what rooftop solar actually costs in Kerala after subsidy →
PM Surya Ghar Subsidy – Does Your 3BHK Qualify?
Yes, almost certainly. Here’s the quick eligibility check:
- You own a residential property (3BHK qualifies)
- You have an active KSEB or TNEB electricity connection
- You haven’t already received a solar subsidy on this connection
- You install through an MNRE-empanelled solar company
The subsidy amount:
- 1kW system: ₹30,000
- 2kW system: ₹60,000
- 3kW and above: ₹78,000 (maximum)
So for a 5kW system, you still only get ₹78,000, the same as a 3kW. That’s why many homeowners going for 4–5kW check the math carefully: the extra capacity beyond 3kW has no additional subsidy.
The application is done online through the PM Surya Ghar portal. A good installer handles this paperwork for you as part of the process.
Which Solar Panel Brand Should You Choose?
For a 3BHK in Tamil Nadu or Kerala, you don’t need to overthink this. Focus on these three things:
- Panel efficiency: Look for panels above 20% efficiency – Waaree, Adani, and Tata all offer options in this range in 2026.
- Warranty: 25-year performance warranty and 10-year product warranty are standard. Don’t accept less.
- Technology: TopCon and bifacial panels are worth it if your budget allows they perform 8–12% better in low-light and cloudy conditions, which matters in Kerala’s monsoon months.
For most 3BHK homeowners, a 540W–575W TopCon panel from Waaree or Adani is a reliable, cost-effective choice in 2026.
How Long Does Installation Take?
Once you confirm the order, here’s a typical timeline:
- Survey and design: 1–3 days
- Installation: 1–2 days
- Net meter application (KSEB/TNEB): 2–4 weeks
- Subsidy disbursal (after net meter): 4–8 weeks
Your system starts generating solar power from day one of installation. The net meter application runs in parallel and doesn’t delay your savings.
What Should You Do Next?
If you’re a 3BHK homeowner in Tamil Nadu or Kerala reading this, here’s what I’d suggest:
- Pull out your last 3 electricity bills and find your average monthly units
- Based on that, decide between a 3kW or 5kW system (most 3BHKs with 1 AC = 3kW, with 2 ACs = 5kW)
- Check your terrace area – you need at least 180 sq. ft for a 3kW system
- Get a free site survey done – a good solar company does this at no charge
- Confirm the installer is MNRE-empanelled so your PM Surya Ghar subsidy goes through cleanly
Solar for a 3BHK is one of the clearest financial decisions you can make in 2026 in this region. Electricity tariffs are rising, sunlight is abundant, and the subsidy genuinely cuts the upfront cost significantly.
The only thing that doesn’t make sense is waiting another year.
Kondaas Automation is a solar installation company serving homeowners across Kerala and Tamil Nadu. For a free site survey and system quote for your 3BHK, contact the Kondaas team.
FAQs
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Can a 3kW solar system run a 1.5 ton AC in a 3BHK?
Yes, but not exclusively. A 3kW system generates around 12–15 units per day. A 1.5 ton inverter AC uses roughly 5–7 units in 6–8 hours. So your AC can run on solar during daytime, but you’ll draw from the grid at night. If AC is your primary concern, a 5kW system gives you more headroom.
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How much does a 5kW solar system cost in Kerala after subsidy in 2026?
A 5kW on-grid solar system in Kerala costs ₹2.4L–₹3.2L before subsidy. The PM Surya Ghar subsidy is capped at ₹78,000 (applicable up to 3kW). After subsidy, most homeowners pay ₹1.7L–₹2.5L depending on panel brand and installer. Payback period is typically 4–6 years.
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Is a 3kW solar system enough for a 3BHK home?
It depends on your usage. If your monthly bill is under 250 units and you run one AC occasionally, 3kW is sufficient. If you run two ACs or your bill crosses 300 units regularly, go for 5kW. The extra cost difference after subsidy is roughly ₹70,000–₹90,000, but you’ll recover it faster with higher generation.
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How many solar panels are needed for a 3BHK house?
For a 3kW system you need 8–9 panels (using 375W–400W panels) covering around 180 sq. ft of roof. For a 5kW system, 13–15 panels needing around 300 sq. ft. Most 3BHK terraces in Kerala and Tamil Nadu have more than enough space.
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Does the PM Surya Ghar subsidy apply to apartments and flats in Tamil Nadu and Kerala?
Yes, if you have an individual electricity meter and own the flat, you’re eligible. Common terrace installations in apartments require society approval and a shared net meter arrangement it’s more complex but doable. Independent 3BHK houses with their own KSEB or TNEB connection have a straightforward application process.