Tamil Nadu
One licensee, a bi-monthly telescopic tariff and a free-unit allowance that decides whether solar pays you back at all. Here is how it actually works, city by city.
Most solar companies run the same pitch in every state. That does not survive contact with Tamil Nadu's tariff structure, and it is the reason a lot of Tamil Nadu homeowners end up with a system that never pays for itself.
Three things make this state its own market:
The honest version: if your household uses under roughly 200 units per bi-monthly cycle, rooftop solar will not pay for itself in Tamil Nadu, and we will tell you so rather than sell you one. The economics here work above that threshold, and they work extremely well for commercial and industrial connections that receive no free units at all.
Tamil Nadu's domestic tariff has a hard threshold at 500 bi-monthly units. Sit at or below it and the household receives the larger free-unit allowance. Cross it — even by a single unit — and the free allowance is cut and the lower slabs reprice upward. The bill does not rise proportionally; it jumps.
For a household hovering just above that line, the most valuable thing a rooftop system does is not save units at the margin. It is pulling total consumption back under 500 and restoring the entire Tier 1 structure. That single effect is frequently worth more than the units themselves, and almost no quotation in this state models it.
The estimator on this page does. Set your bi-monthly units and it will tell you which side of the cliff you are on, and whether solar moves you across it.
Commercial and industrial connections. They receive no free units, they pay a flat and considerably higher rate, and critically they consume during daylight hours. A knitwear unit in Tiruppur running looms from morning to evening self-consumes almost everything its roof generates, and a self-consumed unit is worth full retail tariff while an exported one settles at a much lower rate.
That is why our Tamil Nadu work is weighted towards manufacturing, processing, institutions and larger independent homes, rather than the residential-first approach that suits Mumbai.
Indicative. Models the TNERC telescopic domestic slabs, the bi-monthly cycle and the free-unit tiers at 138 units per kW per month, at 86 sq ft of shadow-free roof per kW. Costs shown are the full installed cost, with no capital grant assumed. Slab rates change with each tariff order — verify against your latest EB bill before relying on these figures.
Cities we cover
Each city page covers the local yield, the building stock, the industries that drive demand there, and the specific things that go wrong on roofs in that area.
Chennai is the hardest and the most valuable rooftop market in Tamil Nadu: dense apartment stock, a coastal salt load that destroys under-specified…
Coimbatore has the best combination in Tamil Nadu of strong irradiation, a milder climate that keeps panels operating closer to their rated…
Madurai has some of the highest solar irradiation of any major city in Tamil Nadu, and a housing stock dominated by independent buildings with clear,…
Trichy combines high irradiation with a heavy-engineering base built around BHEL and its ancillary network — exactly the daytime-load profile that…
Salem's steel, sago and powerloom units run daytime shifts on commercial and industrial tariffs, and the district's irradiation is among the highest…
Tiruppur is the best commercial rooftop solar market in Tamil Nadu and it is not close. Knitwear units run their machinery through the daylight…
Erode's powerloom clusters, turmeric and textile trading businesses and cold storage units all carry daytime loads on commercial tariffs, and the…
Vellore's demand is driven by its healthcare and education institutions, which run large, steady daytime loads, alongside a residential belt of…
Process
One licensee statewide means one predictable process. These are the stages and the timelines TNERC holds TANGEDCO to.
Your system capacity cannot exceed your sanctioned load. This is the single most common reason a Tamil Nadu application is rejected, and it is checked before we design anything.
Net metering application filed with your TANGEDCO service connection number, with all supporting documentation prepared and checked by us.
Typically around 15 days. TNERC requires net metering applications to be processed within 30 days of a complete submission, and delays beyond that can be escalated to the consumer grievance cell.
Sanction usually follows within about 10 days. Installation runs in parallel — two to four days on a residential roof, longer on an industrial shed needing structural work.
Around 20 to 25 days for the agreement and meter installation. Export credits are netted against imports each bi-monthly cycle, with surplus carried forward.
Monitoring app login, commissioning certificate and warranty documentation handed over, and the first cleaning visit scheduled against the local soiling rate.
Straight answers
It depends entirely on your consumption. The state's free-unit allowance means a low-consumption household may already be paying close to nothing, and solar cannot save money that is not being spent.
Above roughly 500 bi-monthly units the picture changes sharply, because the free allowance shrinks and the higher slabs begin to apply. Commercial and industrial connections receive no free units at all, which is why solar pays fastest there.
Plan for roughly 86 square feet of shadow-free roof per kW. A 3 kW system needs about 258 sq ft; a 10 kW system about 860 sq ft.
Temple, church, mosque and gurudwara roofs are usually generous on area but interrupted by domes, towers, tanks and vents, so usable area is measured rather than estimated.
Not more than your sanctioned load. A connection with a 3 kW sanctioned load cannot have a 5 kW system approved for net metering. If your consumption justifies a larger system, load enhancement is a separate application that has to be completed first — we handle it before designing.
Roughly 45 to 55 days of TANGEDCO process running alongside installation, and 90 to 110 days from first application to a commissioned, metered system for a commercial project. Residential systems usually complete faster.
They are netted against your imports each bi-monthly cycle and any surplus carries forward. Whatever remains at the annual settlement is paid at the buyback rate, which is significantly lower than the retail tariff you avoid by self-consuming. This is why we size against your load curve rather than your roof.
