Face the equator. True south in the northern hemisphere, true north in the southern hemisphere. That single choice matters more than fine-tuning the tilt.
Start with 0.87 × your latitude. It is a robust annual rule of thumb, not a precision optimum. A few degrees either way usually changes annual yield by less than 1%.
Seasonal tilt is a small bonus, not a redesign. Adjusting twice a year can add a few percent in places with strong seasonal sun angles; on a low-slope roof it is often not worth the hardware.
What the tilt and site calculator answers
This tool turns your coordinates into practical mounting advice: which way to face the panels, how steep to mount them, how much sun the site receives, how hot and windy it gets, and what that means for production. It is the “where and how” step before the electrical and financial ones.
It reports:
- Optimal azimuth — the compass direction for maximum annual exposure.
- Best fixed tilt — one angle for the whole year.
- Summer and winter tilts — flatter and steeper alternatives.
- Climate zone, temperature range, wind and insolation — the conditions the equipment will live in.
- Monthly sun path and daylight — why production swings between seasons.
Direction: the decision that matters most
Solar panels produce most when the sun’s rays strike them perpendicularly. Over a year, that happens on average when the array faces the equator:
| Hemisphere | Best fixed direction | Why |
|---|---|---|
| Northern | True south (180°) | The sun’s arc is centred south of the zenith. |
| Southern | True north (0°) | The arc is centred north of the zenith. |
| Near the equator | Either, depending on season | The annual penalty for a small offset is modest; local weather and load shape matter more. |
East and west orientations produce less annual energy but shift generation into the morning or afternoon. That can be valuable if your utility pays more at peak times or if you want to flatten the midday export curve. It is a deliberate trade, not a mistake — but it should be modelled, not assumed.
Tilt: the 0.87 rule and its limits
For a fixed annual mount, a widely used starting point is:
Summer tilt ≈ fixed tilt − 10°
Winter tilt ≈ fixed tilt + 10°
At latitude 31.5° (Lahore), that gives a fixed tilt of about 27°, a summer angle of about 17° and a winter angle of about 37°. The logic is simple: a flatter angle collects more of the high summer sun; a steeper angle faces the low winter sun more directly.
The rule is a compromise, not a law. The true optimum varies by roughly ±5–10° depending on local climate, atmospheric dust, cloud patterns and whether the site has snow. A 5° error near the optimum is usually worth well under 1% of annual yield. A 20° error can cost several percent, and a badly oriented array can lose 10–20%.
Fixed versus seasonal tilt
Adjusting the angle twice a year can add roughly 3–8% in regions with a pronounced seasonal sun path. Whether it is worth it depends on the mounting hardware and the labour:
- Adjustable frame on a flat roof: plausible. The hardware exists and the change is a twice-yearly task.
- Flush-mounted pitched roof: usually not. The panels follow the roof, and changing the pitch means rebuilding the mount.
- Ground mount: often the best candidate, especially if the frame is designed for seasonal positions.
- High-latitude sites with long summer days: the seasonal bonus is larger; near the equator it is small.
If the three tilt bars in the calculator are close together, seasonal adjustment is not worth the complexity. If the winter bar is much steeper and your winter production matters, it may be.
A worked example
Take a site at latitude 31.5° in a sub-tropical climate, with a clear south-facing roof:
Summer tilt = 27 − 10 = 17°
Winter tilt = 27 + 10 = 37°
Planning yield band ≈ 135 kWh/kWp/month ≈ 1,620 kWh/kWp/year
A 10 kWp array at that orientation might produce around 16,200 kWh/year in a typical year, before site-specific shading and soiling. If the roof instead faces east or west, expect a lower annual total but a different hourly shape. If it faces north in the northern hemisphere, the penalty is severe and the design should be reconsidered.
Use the yield calculator to turn the tilt and direction into a monthly production profile. The tilt tool tells you where to point; the yield tool tells you what you get.
Heat, wind and climate
Temperature affects output, not just comfort. Panels lose roughly 0.35% of power per degree Celsius above 25 °C, so a hot site produces less on its hottest afternoons than the nameplate suggests. Cooler months often perform better per unit of sunshine. The calculator shows monthly high and low temperatures so you can see the swing.
Wind matters for mounting, not generation. A site with a high five-year peak wind speed needs appropriate fixings, rails and wind-load calculations. The calculator reports the recorded peak and typical breeze as a planning input, not as a structural approval.
Insolation — the solar energy arriving on a horizontal surface — is the raw resource. If it stays high for most of the year, the site is a strong candidate and a flatter fixed tilt is usually fine. If it collapses in winter, a steeper cold-season angle or a larger array may be needed to carry the load through those months.
Where the advice stops
Use the result to choose a sensible orientation and to sanity-check an installer’s proposal. If the roof pitch is fixed, the practical question is not “what is the perfect tilt?” but “what does this pitch cost me versus a flush mount or a tilted frame?” That comparison belongs in the yield model.
Frequently asked questions
Which direction should solar panels face?
In the northern hemisphere, true south (azimuth 180°) gives the highest annual output for a fixed mount. In the southern hemisphere, true north (0°) is best. East and west orientations produce less annually but shift generation to morning or afternoon, which can suit time-of-use tariffs or evening loads.
What is the best tilt angle for solar panels?
A good starting point is 0.87 × your absolute latitude. At 30° latitude that is about 26°; at 40° it is about 35°. The true optimum varies by ±5–10° with local climate, and a few degrees of error usually costs less than 1% of annual yield. The calculator returns the value for your coordinates.
Should I change the tilt between summer and winter?
It can add roughly 3–8% in places with a strong seasonal sun path, but only if the mounting hardware makes it practical. Flush-mounted pitched roofs are not worth rebuilding twice a year. Adjustable flat-roof or ground mounts are better candidates. If the summer and winter angles are close, the gain is small.
Is a flat roof bad for solar?
No, but it needs tilted mounting and row spacing. A flat mount collects less annual energy at most latitudes and lets dust and water sit on the glass. A 10–20° tilt is common on flat roofs; the exact angle depends on latitude, row spacing and wind loading. The roof space calculator accounts for the extra area this requires.
Does heat reduce solar panel output?
Yes. Panels are rated at 25 °C cell temperature and lose roughly 0.35% of power per degree above that. A hot roof can reach 60–70 °C, which is a meaningful derate on the hottest afternoons. Cooler, windier sites perform better per unit of sunshine, and the yield calculator models the temperature effect hour by hour.
How much does the wrong direction cost?
It depends on the offset. A 10–15° azimuth error from true south usually costs only a few percent. East or west instead of south can cost roughly 10–20% of annual yield in many climates. North-facing in the northern hemisphere can lose far more and may not be worth installing without a specific reason.