What size solar system does your home need?
Use your electricity bill, roof space and sanctioned load to choose the right solar system for your Chennai home, without overspending or under-sizing.
Start with your electricity bill
TNPDCL bills homes every two months. Find the units consumed on your last few bills, divide by two to get your monthly use, and take an average across summer and winter.
In Chennai, each kW of well-installed solar produces roughly 120 units a month on average. So a quick estimate is:
System size (kW) ≈ monthly units ÷ 120
Quick sizing table
| Average monthly use | Bi-monthly use (on your bill) | Suggested system | Typical home |
|---|---|---|---|
| Up to 150 units | Up to 300 units | 1–2 kW | Small home, fans and lights, no AC |
| 150–300 units | 300–600 units | 2–3 kW | Family home with one AC |
| 300–450 units | 600–900 units | 3–4 kW | Two ACs, water heater, washing machine |
| 450–650 units | 900–1,300 units | 4–5 kW | Larger house or villa |
| Above 650 units | Above 1,300 units | 5 kW and above | Villa with several ACs, EV charging |
The subsidy reaches its maximum of ₹78,000 at 3 kW, so 3 kW is a common choice for average homes. See the subsidy guide.
Check your roof space
Plan for around 100 square feet of shade-free roof per kW. A 3 kW system needs about 300 sq ft, and a 5 kW system about 500 sq ft. Water tanks, staircase heads and nearby trees or buildings that cast shadows reduce usable space.
If your terrace is also used for drying clothes or functions, a raised structure lets you keep using the space under the panels.
Check your sanctioned load
In Tamil Nadu, the solar system on a home connection cannot be larger than its sanctioned load. Your sanctioned load is printed on your electricity bill. If you need a bigger system, apply to TNPDCL for a load increase first. We check this during the site visit. Read more in our net metering guide.
Plan for the next few years
If you plan to add an air conditioner, an induction stove or an electric car, size the system for that future load now. Adding panels later is possible but costs more per kW than getting it right the first time.
Frequently asked questions
How many units does a 3 kW solar system produce in Chennai?
Roughly 360 units a month on average, more in sunny months and less during heavy monsoon weeks.
How much roof space do I need for 5 kW?
About 500 square feet of roof that stays free of shade from around 9 am to 4 pm.
Can I install a system bigger than my sanctioned load?
Not under net metering for homes. Apply to TNPDCL to increase the sanctioned load first, then install the larger system.
Will solar run my air conditioner?
Yes. A grid-connected system powers everything in your home during the day, and the extra units it exports offset what you use at night.