The best tilt and direction for solar panels (and how much it really matters)
Which way should solar panels face, and at what angle? See how direction and tilt change yearly output, and why east-west roofs and flat roofs still work well.
Direction (installers call it azimuth) and angle (tilt) are the two things that decide how much sunlight a panel collects over a year. They matter, but much less than most people fear. A roof that is "not perfect" often loses only a few percent.
Which direction should panels face?
The ideal is to face the equator:
- Northern hemisphere (India, Europe, the US): face south.
- Southern hemisphere (Australia, South Africa, most of South America): face north.
Moving away from that direction costs less than you might expect. These are typical figures for a moderate tilt at mid latitudes:
| Facing (northern hemisphere) | Yearly output compared with due south |
|---|---|
| South | 100% |
| South-east or south-west | about 95–97% |
| East or west | about 80–88% |
| North | about 55–70% (usually not worth it) |
The exact numbers depend on your latitude and tilt. The flatter the panels, the less direction matters. A panel lying flat does not care which way it "faces" at all.
What is the best tilt angle?
For the most energy over a whole year from a fixed panel, the classic rule is tilt ≈ your latitude. In practice the best angle is often a little lower than that, because summer days are longer and hazy skies favour flatter panels.
| Place | Latitude | Good fixed tilt |
|---|---|---|
| Chennai | 13° N | 10–15° |
| Jaipur | 27° N | 20–27° |
| Delhi | 29° N | 22–28° |
| Madrid | 40° N | 30–35° |
| London | 51° N | 35–40° |
The important part is that the curve is flat around the best angle. Being 10–15° away from the ideal tilt usually costs only around 2–5% of the yearly energy. So on a pitched roof you almost always mount panels flush with the roof. The extra cost and wind load of propping them up rarely pays off.
Flat roofs: tilt or not?
On a flat roof you choose the angle with racking, and there is a trade-off:
- Steeper tilt (15–25°) gives more energy per panel and helps rain wash off dust. But the rows shade each other, so they must be spaced further apart and fewer panels fit.
- Low tilt (5–10°) lets you pack rows close together. You get more panels and more total energy from the same roof, though each panel produces a little less.
- East-west layouts put pairs of low-tilt panels back to back. They fit the most panels on a flat roof and spread generation across the morning and evening, which suits homes that use power at those times.
As a rough guide, keep a gap between rows of about 2–3 times the height of the raised edge of the panel in front. That avoids shading around midday in winter.
Does it matter if my roof faces east and west?
Not as much as people think. An east-west roof with panels on both faces will produce somewhat less per panel than a perfect south roof. But it:
- usually fits more panels, because both faces are used;
- produces power earlier and later in the day, closer to when households use it;
- puts less strain on the inverter at midday.
For homes that use most of their solar power themselves, east-west can be just as good financially.
Shade beats everything
A perfectly angled panel in the shade of a water tank or a neighbour's tree is worse than a slightly misaligned one in full sun. Before worrying about the last few degrees, check:
- trees, chimneys, parapet walls and nearby buildings;
- the low winter sun, which casts much longer shadows;
- obstacles on the roof itself, such as water tanks, lift rooms and solar water heaters.
Try different layouts on your roof
In Solarqivo each panel group can have its own tilt and direction. You can lay racked panels on a flat roof at 10° facing south, try an east-west layout next to it and compare the yearly generation. The 3D view shows where shadows fall at any date and time, so you can spot shading problems before installation.
Next: how many panels fit on your roof and how to read a solar proposal.