Case study: Perambalur farm — 25 HP pump ku off-grid solar, ₹18k/mo diesel eliminate

**Client profile:** Perambalur district Veppanthattai block la 8-acre coconut + banana intercrop farm. Owner N. Sundar (35), second-generation farmer. Farm depth 180 ft borewell, water table 90 ft, 25 HP submersible pump irrigation ku primary source.

**Problem — diesel dependency:** grid connection illa (nearest LT line 2.4 km). 25 HP pump run panna 3-cylinder diesel genset (45 kVA), daily 4-5 hours operation ku 40 liters diesel = ₹4,000/day. Monthly ₹18,000-22,000 diesel bill. Peak summer la genset 6 hours run — ₹26,000/month.

**Additional pain points:** genset noise + smoke → nearby farm complaints, engine oil change ₹4,500 every 250 hours, breakdown la parts 3-4 day supply delay Trichy la, farm quarters (worker family 3 members) power ku separate small genset.

**SVN site survey findings:** roof space limited (thatched sheds), so ground-mount preferred. Sunny hours 6.5 daily average, no shading issue. Soil sandy loam — mounting foundation straightforward. Pump specs: 25 HP × 0.746 kW/HP = 18.65 kW rated, actual load 15-16 kW steady.

**System design decision — off-grid vs grid-tied:** grid extension quote ₹4.8 lakhs (TANGEDCO estimate 4 months) + monthly bill + genset backup still needed. Off-grid solar + battery cheaper long-term. Solar direct-drive impossible for 25 HP inductive load — VFD (Variable Frequency Drive) + battery buffer mandatory for smooth start.

**Final BOM (Bill of Materials):** 15 kW solar array (28 × 540W Waaree bifacial DCR panels) + Deye 16 kW off-grid hybrid inverter with VFD compatibility + 48V/600Ah LiFePO4 bank (Pylontech, 28.8 kWh usable) + ground-mount galvanized structure + DC/AC breaker box + earthing pit × 4 + 4G monitoring modem.

**Cost breakdown:** panels ₹3.36L (₹22/W × 15,120W) + inverter ₹2.15L + battery bank ₹2.30L + structure + civil ₹85k + wiring + protection ₹42k + install labour ₹30k + monitoring + AMC year 1 ₹22k = ₹9.60 lakhs turnkey.

**PM-KUSUM Component B subsidy math:** 5 HP-25 HP pumps ku 60% subsidy (30% central + 30% state) or 30% subsidy for extended system. 25 HP direct pump replacement approved: subsidy ₹5.76L. Farmer contribution ₹1.44L (15%) + bank loan ₹2.40L (25%) at 7% via Canara Bank agri loan.

**Actual out-of-pocket:** ₹1.44L own funds + ₹2.40L loan (EMI ₹4,720 × 60 months). Net cash flow from month 1 positive — old diesel ₹18k saved, EMI ₹4.7k, monthly surplus ₹13,300.

**Install timeline:** subsidy approval 38 days (SVN application + document collection) → panel + inverter procurement 12 days → ground mount civil + earthing 4 days → panel + electrical install 3 days → inverter + battery commissioning 2 days → pump VFD integration + test 1 day → SCADA + remote monitor 1 day → total 61 days start to power-on.

**Post-install operational data (12 months):** average daily generation 62-68 units. Pump consumption 45-52 units. Excess 15-20 units farm quarters (fans, lights, TV, mixer, 1.5 ton AC summer). Battery cycles 340 in year 1 (85% DoD avg). Zero grid dependency, zero diesel purchased.

**Financial result:** monthly diesel savings ₹18,000. Loan EMI ₹4,720. Net monthly gain ₹13,280. Over 60-month loan tenure = ₹7.97L cumulative gain, after loan closure ₹18k pure monthly savings for 15+ more years = ₹32L lifetime benefit vs ₹9.6L investment (₹1.44L own money).

**Payback math (own money basis):** ₹1.44L own investment / (₹18k − ₹4.72k EMI) = 10.8 months to cover own money. Full system payback (including subsidy value) 4.2 years.

**Learnings for other farmers:** (1) Agri pump loads = solar's perfect match — daytime peak demand + generation align. (2) VFD investment critical for HP pumps — soft-start eliminates inrush current, battery smaller-a plan pannalam. (3) PM-KUSUM Component B application ku land record + borewell certificate + existing diesel receipt (proof of need) prep pannunga munnadi. (4) Ground-mount thatched shed farms ku better than roof — cleaning easy, shading control.

**SVN agri-solar footprint:** 140+ pump systems installed Perambalur, Ariyalur, Pudukottai, Karur, Namakkal 2020-2026. Free site visit + PM-KUSUM application handling. Reference visits arrangement possible before booking.