What is Balance of System (BOS)?

Balance of System (BOS) refers to all components of a solar installation except the PV modules themselves. BOS costs typically represent 40–60% of a complete rooftop system price and 30–45% of a utility-scale project.

BOS component categories

Power electronics

• String inverters / central inverters / microinverters
• Solar charge controllers (off-grid)
• Hybrid inverter (with battery storage)

Racking and mounting

• Roof-mount rails, clamps, and anchors (residential)
• Ground-mount galvanised steel structures (utility)
• Single-axis trackers (utility premium)

Wiring and protection

• DC cables (4 mm² / 6 mm² UV-rated solar cables)
• MC4 connectors, junction boxes
• DC SPDs (surge protection), AC MCBs, RCCB, isolators
• Earthing and lightning protection (CEA 2010 compliant)

Monitoring

• Generation meter, net meter (DISCOM supplied)
• Data loggers and remote monitoring platforms

BOS benchmark costs

MNRE FY 2024–25 benchmarks ₹35,000–42,000/kWp total installed cost, with BOS accounting for ₹16,000–20,000/kWp.