Solar site survey checklist: what to capture before you quote

A rooftop quote goes wrong at the survey, long before the proposal desk sees it. Miss the water tank, the phase count or the earth pit and you re-quote or send the engineer back. This solar site survey checklist follows the order a surveyor meets things on a residential or small-commercial roof. Walk it in that order and the first visit can be the last.

Solar site survey checklist: roof, shade and structure

Roof type and condition

Record the roof type (RCC, tin shed, tile, asbestos or open ground), its age and its condition. MNRE's technical specification for PM Surya Ghar lists three rooftop structure types: ballast, tin shed and RCC elevated. For ballast it says the structure must be non-invasive and any penetration of the roof avoided. On an RCC terrace, ask early whether the customer will allow drilling, and photograph the waterproofing layer, cracks and ponding marks. On a tin shed, the same specification fixes the structure to the purlins, so note their condition and any corroded sheets.

Usable area on each roof plane

A solar site survey checklist should treat every roof plane as its own record. Measure the shadow-free area plane by plane. Subtract the water tank, stair headroom, vents, a solar water heater and a walkway along the edge. Trina Solar's module manual says to leave a safe working area between the roof edge and the array.

For a rough cross-check, SECI's rooftop FAQ says a 1 kW system needs about 12 square metres (130 square feet) of flat, shadow-free area, preferably south-facing. It adds that the real figure depends on radiation, weather and roof shape. That FAQ is old, so use the number to sanity-check your own measurement, not as a design input.

Shading and orientation

Note the direction and tilt of every plane separately. Trina's manual says modules at different orientations can be connected to separate inverters or MPPT inputs to optimise output. A single "roof direction" field cannot capture that.

For shade, MNRE's specification asks for complete shadow-free operation during generation hours. Stand where the array will go and look east, south and west. Note parapets, the neighbour's tank, trees and any floor the customer plans to add, and ask about construction next door.

Structure and strength

MNRE's sample vendor agreement puts the "feasibility study of roof, strength of roof and shadow free area" inside the vendor's site survey. Record the number of floors, the building's age and any visible damage, and note who signs off roof strength.

Measure the headroom if the customer wants a raised structure over the terrace. The July 2024 PM Surya Ghar specification wants at least 8 feet of ground clearance at the lowest point of an elevated structure before it qualifies for central subsidy.

Load, meter and distribution board details

The electrical half of the solar site survey checklist starts with the bill and ends at the distribution board.

• Consumer account number. A PM Surya Ghar application needs a valid one, so copy it as printed and note the DISCOM.
• Sanctioned load, with its unit (kW, kVA or HP), and the connected load you can see on site. How system size relates to sanctioned load depends on the state, so record both and confirm with the DISCOM.
• Phase. On a three-phase supply, check at the board that all three phases are live.
• Meter number, meter type and the last 12 months of units from the bill.

MNRE's specification calls for a net or smart meter to record import and export, plus a generation meter if state regulations require one. The DISCOM installs them.

The Electricity (Rights of Consumers) Rules exempt systems up to 10 kW from the technical feasibility study. The Press Information Bureau reported the change on 23 February 2024. MNRE's guidelines say the consumer uploads feasibility documents where state rules still require them, until the regulator or DISCOM applies the exemption. Ask which route applies.

Distribution board and earthing

Open the main distribution board with the customer present and photograph it. Check for a spare way for the solar breaker. Note the busbar and breaker ratings, any burnt terminations and the cable distance from the meter.

Earthing gets its own line on the sheet. The PM Surya Ghar specification for residential subsidy systems asks for grounding under IS 3043-2018 and earth resistance never above 5 ohms. From 10 kW up, it wants three separate earth pits for DC, AC and the lightning arrester. It also says the lightning arrester must not sit on the module mounting structure. Locate the existing earth pit and check whether open ground near the array can take new ones. Note any lightning arrester already on the building.

Inverter location and cable routes

Two items on the solar site survey checklist decide whether the design can be built: the inverter wall and the cable route.

Solis's manual for its mini single-phase inverters (version 1.5, 2024) is a fair baseline. It says direct sunlight raises the operating temperature and can limit output. It recommends keeping the unit out of direct sun and rain. It also warns against small closed spaces without airflow. It asks for a wall or strong structure that bears the weight, and the mounting structure must be fireproof. Other makers differ, so read the manual for the inverter you will quote. On site, mark a shaded, ventilated wall near the distribution board. A technician must be able to reach the unit and read its display.

Then walk the cable route from array to inverter and from inverter to board, and measure both runs. Length costs money. MNRE's specification keeps DC cable voltage drop under 2% and caps AC drop at 2%, so a longer run needs a thicker cable. It also wants cables in RPVC pipe or a GI cable tray, tagged. Look for an existing shaft, duct or conduit. Note every point where a cable crosses a parapet or wall, because each crossing is a waterproofing job.

Photos to take and documents to collect

Build the photo list into your solar site survey checklist so every surveyor shoots the same set.

• Each roof plane from its edge, with the whole terrace in frame.
• The horizon to the east, south and west from the array spot.
• Parapet, water tank, stair room and roof access.
• The meter face and number, and page one of the bill.
• The open distribution board, the earth pit and the proposed inverter wall.
• The cable route, including every wall or parapet crossing.
• Cracks and damp patches on the terrace.

For documents, ask for the latest electricity bill. A PM Surya Ghar file also needs the consumer's bank account details, shown by a cancelled cheque image, e-statement or passbook scan, and loan account details if the system is financed. The MNRE residential guidelines set this out. Identity and ownership papers vary. Check the current list on the national portal and with the DISCOM before you promise a timeline.

Questions that save a second visit

A solar site survey checklist ends with questions for the customer. These settle most of what a second trip would have found.

• Does the person signing own the roof, and who holds the terrace key? MNRE's sample agreement makes roof access during installation and maintenance the customer's job.
• Is there power and water on the roof? The same agreement lists electricity during installation and water for cleaning the panels.
• Where will material be stored until installation? The agreement lists secure storage.
• Is any renovation, new floor or re-waterproofing planned? Each can move the array.
• Does a DG set or inverter backup feed the same board? Note its capacity and make.
• Is the connection residential or commercial? As of the July 2024 guidelines, central subsidy is not given to non-residential consumers, so say so before you quote. For a shop or small factory, also record the tariff type and whether the load runs by day or night.

Whatever tool you use, the solar site survey checklist stays the same. If you keep surveys in SolarERP, the Solar EPC module has a site survey form for most of the fields above. It covers roof type and condition, usable area, shadow notes, direction and tilt, sanctioned load, consumer and meter numbers, and cable lengths. It takes photo uploads for the roof, meter, bill, LT panel, hand sketch and site. It also holds the site's map coordinates and stores customer and engineer signatures. You can mark a visit "revisit required", add your own fields and print a PDF report. The staff app can file a visit on a lead before an order exists. When you confirm the order, the survey moves to the project.