Solar panels should face true south in the northern hemisphere and true north in the southern hemisphere. Anyone asking what direction should solar panels face runs into a second question almost immediately. True south and the south your compass shows are rarely the same bearing.
That gap has a name, magnetic declination, and it is the most common reason a well planned array ends up pointed slightly wrong. The fix costs nothing but a few minutes of checking. Orientation also interacts with tilt, and the angle you set the panels at carries more weight across a full year than the compass bearing does.
Quick Answer
Point panels at true south in the northern hemisphere, true north in the southern. Correct the compass reading for local magnetic declination first, because a compass points at magnetic north, not the geographic pole. A shift toward west can suit households on time-of-use rates, since it pushes production later into the afternoon.
Azimuth at a Glance
| Bearing | Where it points | What it suits |
|---|---|---|
| 180 degrees | True south | The default target in the northern hemisphere, and the bearing that gathers the most sun across a full year |
| 135 degrees | Southeast | Morning heavy production, useful where afternoon shade falls across the array or where household load peaks early |
| 225 degrees | Southwest | Afternoon and early evening production, a common compromise for time-of-use billing |
| 90 degrees | Due east | Early production only, usually a roof plane you accept rather than choose, often paired with a west facing plane |
| 270 degrees | Due west | Late afternoon peak, the strongest match for evening rates and evening household demand |
Why True South and Compass South Are Not the Same
A magnetic compass points toward magnetic north, which sits some distance from the geographic north pole and drifts over time. The angle between the two is magnetic declination, and it changes depending on where you stand. Across the contiguous United States, declination runs roughly fifteen degrees east to fifteen degrees west.
That means a compass in one state can be off in the opposite direction from a compass in another. Reading 180 degrees off a raw compass and mounting to it will therefore misalign the array by whatever the local declination happens to be. The error is silent, since nothing about the finished install looks wrong.
NOAA publishes a magnetic declination calculator that returns a local figure from a ZIP code or a set of coordinates. Enter the site address, note the value, and apply it before any hardware goes up. East declination means magnetic north sits east of true north, so true south is found by adjusting the compass reading in the matching direction.
Declination also shifts slowly year to year. A figure written on a plan five years ago deserves a fresh lookup rather than reuse. The correction takes seconds and removes an entire category of avoidable error.
How to Find True South Without a Compass
True south can be located without any compass at all, using the sun and a vertical object. At solar noon, the moment the sun reaches its highest point for the day, a shadow points along the true north to south line. Mark the shadow of a plumb stick or a fence post at that moment and the line is drawn.
Solar noon is not the same as clock noon. It shifts with longitude within a time zone and with daylight saving time, so look up the local solar noon for the date rather than assuming twelve o’clock. Most sunrise and sunset tables list it.
Phone compass apps offer a second route. Many include a true north setting that applies the declination correction automatically, so the reading already accounts for the local offset. Check that the setting is switched on, since the default is often magnetic north.
Satellite imagery gives a third check and is the fastest of the three. Overhead map views are aligned to true north by default, so a roof ridge measured against the image reveals the plane’s real bearing. This works well for confirming what an existing roof already offers before any mounting hardware gets ordered.
Two methods agreeing is a good standard. A shadow line and a satellite view rarely fail together.
When Facing West Beats Facing South
South maximizes the annual energy total, but the annual total is not always what a household is paid for. Utilities on time-of-use rates price late afternoon and early evening electricity higher than midday electricity. A south facing array peaks at midday, precisely when that energy is worth least.
Shifting the array toward southwest or west moves the production curve later. The array generates a little less over the year and more during the expensive window. Whether that trade pays depends entirely on the local rate structure.
Household load follows a similar shape. Cooking, laundry, air conditioning recovery, and vehicle charging cluster in the evening. Self consumption climbs when panel output overlaps that demand rather than pouring into an empty house at noon.
Battery storage weakens the argument, since a battery can move midday production into the evening on its own. Without storage and on a time-of-use tariff, the westward shift becomes a serious option. Run the numbers against an actual bill rather than a general rule.
How Much Direction Actually Matters
Azimuth is more forgiving than most planning conversations assume. Tilt drives the annual total more strongly, because it governs how squarely the panel meets the sun through the seasons. A modest orientation error is a smaller problem than a badly chosen angle.
No honest single figure exists for what a given azimuth deviation costs. The answer depends on latitude, on tilt, on local cloud patterns, and on shading, and it requires site specific modeling to pin down. Any source quoting one universal percentage is describing one location and one roof.
Shading usually outweighs orientation by a wide margin. A chimney or a maturing tree clipping the array during peak hours does far more damage than a bearing off by ten degrees, and partial shade behaves worse than people expect because of how strings share current. Clearing an obstruction is often the higher value move.
Ground mounts remove the roof constraint entirely. With open land, azimuth and tilt both become free choices rather than whatever the building offers. That flexibility is a large part of why ground based racking keeps its appeal on properties with the space for it.
What Trips People Up
Trusting a raw compass reading
The single most common error is mounting to an uncorrected magnetic bearing. Declination is invisible in the field and nothing flags the mistake later. Look up the local figure before marking anything.
Using a phone compass near metal
Phone magnetometers are easily disturbed by roof flashing, rebar, conduit, and vehicles. A reading taken while standing on a metal roof deck can be badly wrong. Step well clear of metal, recalibrate, and take the reading twice.
Chasing perfect orientation on a compromised roof
Effort spent fine tuning azimuth is wasted if a tree shades the array each afternoon. Fixing shade, adding a plane, or moving the array outranks a small bearing correction every time. Deal with the large loss first.
Assuming direct beam sunlight is the only input
Panels also collect diffuse light scattered by cloud and sky, which is why an east facing plane still contributes on an overcast day. Output falls under cloud but does not stop, and the relationship between sunlight and production is less binary than it appears. Panels are rated at 25C, so real world conditions differ from the label in both directions.
Related Reading
Worth reading next: the way bearing and output move together gives useful context for any azimuth decision, laying panels flat on a roof covers the case where tilt is constrained by the structure, and common causes of weak production helps when a finished array falls short of expectations.
Frequently Asked Questions
What direction should solar panels face for the best year round output?
True south in the northern hemisphere and true north in the southern hemisphere. That bearing collects the most sunlight across a full year at any latitude away from the equator. Correct for magnetic declination before setting the array, since a compass points at magnetic north and the offset varies by location.
Is magnetic south good enough for mounting panels?
Usually not, though it depends on where the site sits. Declination across the contiguous United States runs roughly fifteen degrees east to fifteen degrees west, so the error can be substantial in some regions and small in others. Look up the local value on the NOAA declination calculator and apply it before committing.
Does facing east or west ruin an array?
No. East and west facing planes produce meaningfully less than south facing ones but remain viable, especially when paired so that one plane covers morning and the other covers afternoon. West facing arrays can suit time-of-use billing because their peak lands in the expensive evening window.
Which matters more, tilt or direction?
Tilt has the larger effect on the annual total. Azimuth is comparatively forgiving, so a bearing that is a few degrees off costs less than a poorly chosen angle. Both matter far less than eliminating shade across the array during peak production hours.
How is true south found without buying tools?
Mark the shadow of a vertical object at local solar noon, because that shadow lies along the true north to south line. Look up solar noon for the date rather than using clock noon. A satellite map view, which is aligned to true north, confirms the result independently.
Do phone compass apps handle declination automatically?
Many include a true north option that applies the correction, but it is often not the default. Check the setting before trusting a reading. Keep the phone away from metal roofing, conduit, and vehicles, since nearby steel distorts the magnetometer and produces confident but incorrect bearings.
Can orientation be changed after installation?
On a roof, rarely, since the array follows the plane it sits on. Ground mounted racking is different, because the azimuth is set by the frame rather than the building and can be adjusted. That freedom is a practical reason to consider ground mounting when open land is available and row spacing can be planned properly.
