Do you still want your terrace? Plan the layout before you sign.

A solar quote tells you the kW. It rarely tells you what is left of your terrace.

For many Bengaluru homes the terrace is not spare space. It holds the overhead water tank, the clothes line, a few plants, the stairhead room and, on weekends, the family. Panels cover a large part of that surface for 25 years. If nobody plans the layout before installation, you find out afterwards where you can and cannot walk.

This is a planning checklist you can use with any installer. It does not change what system size you need. It changes where the panels go.

Start with how you use the terrace today.

Before the site survey, list what happens up there: tank cleaning, drying clothes, a gym corner, a terrace garden, festival lighting, a future room. Mark these on a rough sketch. Show it to the installer and ask them to draw the panel layout on top of it, instead of the other way round.

How much space do panels actually need?

A common rule of thumb is that each kW needs roughly 8 to 10 square metres of shadow-free area, which is about 80 to 100 square feet. The exact figure depends on the wattage and size of the panels, tilt, row spacing and the shape of your roof, so ask the installer to show the number for your roof and your panel model. Our guide on how much solar your home needs explains how to arrive at the kW first, and the layout comes second.

Flush-mounted or raised?

Panels can sit low on a light structure, or be raised on a taller frame that leaves room underneath. A raised structure can keep part of the terrace usable for drying clothes or storage, and can reduce the heat reaching the slab below. It also uses more steel, needs stronger fixing against wind, and usually costs more. Ask for both options on the quote and ask what the extra cost buys you in your case. Do not accept a raised structure just because it sounds better, and do not accept a low one without checking the headroom for the people who maintain it.

Keep these four things clear.

• A walkway to the water tank and the stairhead. Anyone cleaning the tank or fixing a pipe needs a clear route that does not involve stepping on a panel.
• Access for cleaning panels. You need to reach every row with a hose or a wiper. Rows packed too tightly are difficult to clean, as we explain in cleaning and maintenance.
• The terrace drain outlets. Panels and structures should not block a rain outlet or sit where water pools. See waterproofing and mounting structures for how fixing points should be sealed.
• A margin from the parapet and the edge. Ask what clearance the layout keeps, for wind and for safe working.

Think about shadows you will add later.

A new water tank, a stairhead room, a second-floor extension or a neighbour's building can shade rows that are fine today. The layout should keep the best-lit area for panels and put anything you may add later on the shaded side. Our post on rooftop shading shows how even partial shade can cut a string's output. If you are planning an extension in the next few years, tell the installer now.

Ask for the layout in writing.

When you compare solar quotes, ask each installer for a simple layout drawing that shows panel positions, walkways, inverter location, cable route and the clearances above. Check it against your sketch. A quote with no layout is a quote you cannot compare on the thing you will live with.

The short version.

List how you use the terrace, ask for the layout drawn over your sketch, compare raised and low structures, and keep a walkway, cleaning access, drain outlets and a parapet margin clear. Tell the installer about any tank, room or extension you may add later.