Fixed installation
Which direction should solar panels face?
Short answer
In the northern hemisphere, face a fixed array due true south, 180 degrees. In the southern hemisphere, due true north, 000. Tilt it at roughly your latitude.
A fixed panel wants to spend as much of the day as possible facing the sun, and the sun's daily arc is symmetrical about the meridian. So the best single direction is along the meridian, pointing toward the equator: south if you are north of it, north if you are south of it.
The important detail is that this is true south, not magnetic south. Get that wrong and you can be twenty degrees off before you have started, which is a larger error than most of the optimisations people worry about.
Northern hemisphere, maximum yield · 180°
Method
Step by step
In this order. Each step assumes the one before it is done.
-
01
Find true south, not magnetic south
Look up the magnetic declination for your site once, then either enter it into the compass here and select True north, or apply it by hand to a physical compass reading. Either way you must do it: skipping the correction is how installs end up twenty degrees off before anyone has touched a bracket.
-
02
Set the azimuth
Point the array at 180 degrees true in the northern hemisphere or 000 true in the southern. Being ten to fifteen degrees off costs surprisingly little, typically a couple of percent of annual yield, so do not agonise. Being ninety degrees off is a different matter.
-
03
Set the tilt
For maximum annual energy, tilt the panel at roughly your latitude. Shallower favours summer, steeper favours winter. If you are trying to shave a winter peak, add ten or fifteen degrees to the latitude figure.
-
04
Consider aiming west instead
This is the case where the textbook answer is wrong. If you are paid time-of-use rates that peak in the late afternoon, or you are trying to cover your own evening consumption, a west-facing array generates less in total but more of it when it is worth more. Southwest is a common compromise.
Reference
The bearings
- Northern hemisphere, maximum yield
- 180° S
- Due true south.
- Southern hemisphere, maximum yield
- 000° N
- Due true north.
- Northern hemisphere, evening bias
- 225° SW
- Southwest. Less total, better timed.
How wrong can this be?
Accuracy
Azimuth within about ten degrees of optimal costs under two percent of annual yield for a typical mid-latitude install. The declination error you avoid by using true north is often larger than that, which is the whole point.
Related
Other guides
The basic one
Which way is north?
If you are on a phone, press Start compass and turn until the bearing reads 000. If you are not, and the sun is up, stand with the sun on your right in the morning and you are facing roughly north.
No instrument
Without a compass
Put a stick upright in the ground, mark the tip of its shadow, wait fifteen minutes and mark it again. The line from the first mark to the second points roughly east.
Line of sight
Aim a satellite dish
Look up the azimuth, elevation and skew for your postcode and your satellite, set the azimuth as a true bearing, then fine-tune on signal strength.