Most Common Mistakes Solar EPCs Make — and How to Avoid Them

Most Solar Problems Are Process Problems — Not Technology Problems

The panels work. The inverters work. The technology is mature and reliable. The reason solar systems underperform, face DISCOM rejection, or generate client disputes in India is almost never a technology failure. It is an EPC process failure — something that should have been checked before the first panel was mounted but was not.

1. Skipping shading analysis

A factory in Rajasthan's Mansarovar Industrial Area lost 18% of its annual generation because nearby cooling towers were not accounted for in the system design. The shading was visible on a site visit and would have been caught by any 3D shading simulation tool. The client's first year bill savings were Rs 3.5 lakh lower than the proposal promised — generating a formal complaint and a lost client relationship.

2. No structural assessment before rooftop installation

Solar mounting structures add 15 to 25 kg per square metre to a rooftop. Older buildings — particularly those built before 2000 — frequently cannot bear this load without reinforcement. An EPC who installs on an unassessed structure takes full liability for any structural damage. Beyond liability, a structurally compromised installation can fail in the first monsoon.

3. Poor earthing — especially in sandy soils

In Rajasthan's sandy soil, achieving low earth resistance with standard earthing rods is difficult. Cheap earthing materials and insufficient depth fail within two to three years, leading to inverter failures and safety hazards. The inverter manufacturer's warranty often excludes damage caused by inadequate earthing — leaving the EPC with the liability.

4. No written performance guarantee in the EPC contract

An EPC contract without a specific generation guarantee in kWh per year means every underperforming system becomes a potential dispute. The client expected the savings shown in the proposal. Without a written standard against which performance is measured, the dispute is about expectations versus reality — and expectations are always harder to win than measurements.

5. Undersized DC cables causing voltage drop losses

Undersized DC cables between panels and inverter cause resistive losses that reduce system output. In large commercial installations where cable runs are long, a 1% extra cable loss multiplied over 25 years and thousands of kWh represents substantial lost revenue for the client. This error stems from cost cutting on cabling — the cheapest quote uses the smallest permissible cable size rather than the optimal size for the distance involved.

6. Non ALMM modules in a subsidy linked installation

An EPC who installs non ALMM certified modules in a PM Surya Ghar, PM KUSUM, or net metered installation will have the subsidy claim rejected. There is no retroactive remedy — the client loses Rs 78,000 and holds the EPC responsible. From June 1, 2026, this error extends to cell level compliance under ALMM List II.

7. Installing panels at the wrong tilt or orientation

In India, solar panels should face south for maximum annual generation. Panels facing west or east lose 15 to 25% of annual generation versus south facing equivalents at the same site. Zero tilt flat installations in high dust regions like Rajasthan accumulate dust faster and self clean less from rain, adding 3 to 5% annual soiling losses on top of any orientation loss.

8. No remote monitoring system handed over at commissioning

A solar system without monitoring is a system the client cannot verify is performing as promised. When the inverter fails, dust accumulates, or a string connection loosens, the client often does not notice until the quarterly bill shows disappointing savings. By that point, the performance loss may span several months — and the client blames the EPC.

9. Incomplete handover documentation

An installation is not complete until the client has every document needed to manage the system for 25 years: as built drawings, equipment warranty cards, BIS test certificates, the commissioning report, DISCOM approval letters, net metering agreement, and monitoring credentials. Missing documentation is also one of the top rejection reasons for subsidy claims.

Frequently Asked Questions

Common questions about solar installation quality and disputes from Indian EPCs.

What should I do if a client's system is underperforming after installation?

First, pull the monitoring data and compare actual generation against the design estimate for the same period and weather. If generation is below design by more than 5 to 10%, investigate in order: check for new shading obstructions (construction nearby, vegetation growth), inspect for soiling on panels, review inverter logs for fault codes, check all string connections, and measure string voltages. Document everything. If the shortfall is due to a design error, acknowledge it, propose a correction, and negotiate with the client on compensation. If it is due to equipment failure under warranty, initiate the warranty claim process and give the client a written timeline.

How do I prevent the client from comparing their system's performance to their neighbour's?

Set clear, documented expectations at proposal stage. Include the specific annual generation forecast in both the proposal and the contract. Explain that performance varies by roof orientation, shading, and panel cleaning frequency — and document the client's specific conditions. When you hand over monitoring access, show the client how to read performance ratio rather than raw units, so they understand different systems on different rooftops are not directly comparable.