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Whether you want to reduce bills, avoid load-shedding, or increase property value, a properly designed rooftop solar system can do all three. This guide walks you through the entire process from first idea to a running, net-metered system.

Step 1: Define Your Goal and Constraints

1. Decide your primary goal: bill reduction, backup during outages, or complete off-grid independence.
2. Set a budget range that you are comfortable with.
3. Note roof type, usable area, shading objects (trees, neighboring buildings, water tanks), and any structural limitations.
4. List important appliances that must run during outages (for hybrid/off-grid designs).

Step 2: Collect Your Energy Data

1. Gather the last 12 months of electricity bills to understand kWh consumption and seasonal peaks.
2. Identify your contracted load and tariff slab.
3. Estimate your desired offset: for example, target 70–100% of annual kWh.
4. Note peak load (kW) for inverter sizing.

Step 3: Estimate Solar Resource and System Size

1. Find your typical “peak sun hours” (PSH) for your city. A common planning value is 4.5–5.5 hours per day, but check a reliable source for your location.
2. Use this quick sizing method:
   • Daily energy to offset (kWh) ÷ PSH ÷ system efficiency = DC array size (kW).
   • System efficiency often ranges 0.75–0.85 after real-world losses.
   • Example: If you want to offset 18 kWh/day, PSH = 5.0, efficiency = 0.8:
     • 18 ÷ 5.0 ÷ 0.8 ≈ 4.5 kW array.
3. Check your roof area: modern modules need roughly 5–7 m² per kW (depends on module wattage and layout).

Step 4: Choose System Topology

1. On-grid (grid-tie): Best for maximizing bill savings via net metering. Requires grid availability and permission.
2. Hybrid: Works with grid and batteries. Provides backup plus bill reduction. Slightly higher cost and complexity.
3. Off-grid: Maximum independence with batteries and often a generator. Highest cost; suitable where grid is unreliable or unavailable.

Step 5: Select Core Components

1. Solar panels: Prefer Tier-1 manufacturers with at least 12–15 years product warranty and 25–30 years performance warranty. Consider mono-PERC or TOPCon for higher efficiency.
2. Inverter:
   • On-grid: string inverters or microinverters. Look for multiple MPPTs, anti-islanding, and monitoring.
   • Hybrid: ensure adequate battery compatibility, surge capacity, and islanding mode.
3. Batteries (if hybrid/off-grid): Lithium iron phosphate (LFP) is popular for long cycle life and depth of discharge. Size for your critical load and desired backup hours.
4. Balance of system: DC/AC isolators, surge protection, earthing, lightning protection, mounting structures, DC combiner boxes, cables and connectors (MC4), and conduit.

Step 6: Size the Inverter and Strings

1. Inverter AC rating should be close to the array size; many designs use DC/AC ratio between 1.1 and 1.3 to maximize production.
2. Check module datasheet for Voc and Vmp; ensure string Voc at the lowest expected temperature does not exceed inverter max DC voltage.
3. Match current ratings: string Isc multiplied by safety factor (often 1.25) must be within inverter and combiner input limits.

Step 7: Battery Sizing (If Applicable)

1. Determine critical load power (kW) and backup time needed.
2. Energy required = critical load (kW) × backup hours.
3. Consider round-trip efficiency (e.g., 90–95%) and allowable depth of discharge (e.g., 80–90% for LFP).
4. Example: 1.5 kW critical load × 6 hours = 9 kWh. With 90% round-trip and 90% DoD:
   • Required battery ≈ 9 ÷ (0.9 × 0.9) ≈ 11.1 kWh.

Step 8: Roof Layout and Structure

1. Verify structural capacity with an engineer if needed.
2. Maintain clear walkways, inverter location proximity, and safe cable runs.
3. Orient modules toward the equator with an optimal tilt close to your latitude; adjust for seasonal goals if necessary.
4. Leave spacing to avoid row-to-row shading.

Step 9: Safety and Compliance

1. Incorporate DC and AC isolators, fuses/breakers, surge protection devices, proper earthing, and lightning arrestor where required.
2. Use UV-resistant DC cables, correct cable gauges, and certified connectors.
3. Label all components and cable routes. Keep a single-line diagram on site.

Step 10: Quotation and EPC Selection

1. Request itemized quotations that include brand/model, warranties, installation scope, and after-sales support.
2. Compare total cost of ownership, not only upfront price.
3. Ask for performance guarantees and expected annual yield.

Step 11: Installation, Testing, and Commissioning

1. Mount structures and modules according to manufacturer torque specs.
2. Route DC strings to combiner, then to inverter with correct polarity and protection.
3. Connect AC side to the distribution board with proper breakers and RCDs as required.
4. Perform insulation resistance tests, verify open-circuit and short-circuit measurements, and confirm inverter parameters.

Step 12: Net Metering and Documentation

1. Complete utility applications, single-line diagrams, and compliance certificates.
2. Coordinate utility inspection and bi-directional meter installation where available.
3. Store all manuals, warranties, and commissioning reports.

Step 13: Monitoring, Maintenance, and Upgrades

1. Enable inverter/app monitoring for real-time production and fault alerts.
2. Clean modules when performance drops or soiling is visible; avoid harsh chemicals and clean in cool hours.
3. Schedule annual electrical checks: torque, insulation, earthing resistance, and firmware updates.
4. Plan for future expansion or battery add-on if the inverter supports it.