Size an off grid system in four steps: daily load (kWh), battery = load × days of backup ÷ 0.85 ÷ depth of discharge, panels = load ÷ (sun hours × 0.8) × 1.25, inverter = connected load ÷ 0.8 + 20%. Off grid systems cost about ₹85,000 per kW (±10%) as an indicative turnkey price and get no subsidy.
Step 1: Calculate the Daily Load
Off-grid design starts from energy, not bills. List every appliance with wattage, quantity and daily hours. Worked example, a farmhouse: 4 fans (75W × 12h), 8 LED lights (10W × 6h), fridge (150W × 8h effective), TV (100W × 5h), pump (750W × 1h). Daily energy ≈ 3.6 + 0.5 + 1.2 + 0.5 + 0.75 = 6.5 units/day; connected load ≈ 1,430W. Build yours in the solar load calculator.
Step 2: Size the Battery Bank
With 1 day of autonomy on lithium (0.85 DoD): 6.5 ÷ 0.85 ÷ 0.85 ≈ 9 kWh (about 188 Ah at 48V). Cloud-prone regions should plan 1.5 to 2 autonomy days. Lead-acid at 0.50 DoD needs ~15.3 kWh for the same job. Compare chemistries in the solar battery calculator.
Step 3: Size the Panel Array
The 1.25 factor covers battery charging losses and cloudy-day recovery. At 4.8 sun hours: 6.5 ÷ 3.84 × 1.25 ≈ 2.1 kW, say 4 × 550W panels. Verify recharge speed: 9 kWh through ~1,580W effective panel output refills in about 1.4 sunny days, acceptable with 1 day autonomy (check any combination in the charging time calculator).
Step 4: Size the Inverter and Wiring
Inverter: 1,430W ÷ 0.8 pf × 1.2 headroom ≈ 2,150 VA → a 2.5 kVA, 48V off-grid inverter. The pump's motor start is the surge to respect. Battery cables at 48V carry ~45A; a 5 m run needs about 10 sq. mm copper. Confirm with the inverter size calculator and wire size calculator.
Worked Example: The Complete Bill of Materials
| Component | Specification | Indicative Cost |
|---|---|---|
| Panels | 4 × 550W (2.2 kW) | ₹55,000 – ₹66,000 |
| Battery | 9 – 10 kWh LiFePO4, 48V | ₹1,60,000 – ₹1,85,000 |
| Inverter | 2.5 kVA off-grid, 48V, MPPT | ₹35,000 – ₹45,000 |
| Structure, wiring, install | DC cable, earthing, mounts | ₹25,000 – ₹35,000 |
| Total | ~2.2 kW / 9 kWh system | ₹2.75 – ₹3.3 lakh |
Note the battery dominates the budget, and off-grid systems get no central subsidy. If a grid connection exists at all, a hybrid system is almost always better economics; compare with the cost calculator in hybrid mode.
Off Grid Solar System Price vs On-Grid and Hybrid (3 kW Example)
Indicative 2026 prices for a 3 kW home system of each type, using the standard per-kW rates in our calculators:
| System type | Price | Subsidy | Net price |
|---|---|---|---|
| On-grid (no backup) | ₹1,56,600 – ₹1,91,400 | ₹78,000 | ₹78,600 – ₹1,13,400 |
| Hybrid (battery backup) | ₹1,94,400 – ₹2,37,600 | ₹78,000 | ₹1,16,400 – ₹1,59,600 |
| Off-grid (no grid needed) | ₹2,29,500 – ₹2,80,500 | Not eligible | ₹2,29,500 – ₹2,80,500 |
Off grid costs the most because the battery bank must cover every night and cloudy day, and the panel array is about 25% larger. Where a grid connection exists, hybrid usually gives the same backup for less; price one with the hybrid solar system calculator.
The battery decides most of an off grid budget. The worked example above pairs just 2.2 kW of panels with a full one-day, 9 kWh lithium bank, which is why it costs ₹2.75 to ₹3.3 lakh, more per kW than the standard rate. Size your own battery with the solar battery calculator before comparing quotes.
When Hybrid Beats Off-Grid: The Honest Checklist
Off-grid is a necessity, not a lifestyle upgrade. Choose hybrid instead if any of these is true:
- A grid connection exists at the property, however unreliable it is. Even ten grid hours a day slashes the battery bank you must buy.
- Your load includes daily air conditioning; grid support during heat waves saves lakhs in storage.
- You want the residential subsidy: hybrid qualifies for the full ₹78,000, off-grid gets nothing.
- Monthly consumption exceeds ~400 units; pure off-grid economics deteriorate quickly at scale.
- The site sees week-long monsoon cloud; grid or generator backup beats a second battery bank bought for twenty bad days a year.
Go genuinely off-grid when there is no line to connect to, extension quotes are absurd, or the load is a compact, disciplined farm or cabin profile like the worked example above.
Rules of Thumb for Reliable Off-Grid Design
- Autonomy: 1 day minimum, 2 days where monsoon is severe.
- DoD discipline: lithium to 85%, lead-acid to 50%; deeper cycling shortens life fast.
- Oversize the array, not the inverter: panels are the cheap part; winter recharge speed is the binding constraint.
- Heavy loads by day: run pumps and washing machines in sun hours so they draw from panels, not the battery.
- 48V over 12/24V: above ~1.5 kW, higher bank voltage slashes current, cable cost and losses.