Quick answer
Solar Azimuth is a direction measured in degrees clockwise from true north. For the sun it says where in the sky the sun sits right now; for solar panels it says which way the panel face points, with 180° meaning due south.
The key word is "true". A phone or hand compass points to magnetic north, which can be several degrees off. The difference must be corrected before an azimuth goes into a design tool.
Quick facts
The key facts about solar azimuth, with sources:
Key takeaways
- There are two azimuths in solar: the sun’s, which moves all day, and the panel’s, which is fixed.
- Both count clockwise from true north. 180° is due south.
- A compass reads magnetic north. In Charleston, SC, true south shows as about 188° on a compass.
- In PVWatts, a higher azimuth shifts output toward the afternoon, a lower one toward the morning.
- Measure from the ground or from aerial images. Never climb a roof to take a reading.
Two azimuths: the sun’s and your roof’s
Sun azimuth tells you where the sun is along the horizon. NOAA defines it as the angle "clockwise from true north to the point on the horizon directly below the object".
It changes every minute. At sunrise the sun is in the east, around noon it is near south, and at sunset it is in the west.
Surface azimuth (the panel’s) is the direction the panel face points. It does not move on a fixed roof. The solar panel orientation page shows how different roof faces perform. This page is about the number itself: how it is defined, corrected and measured.
Production software uses both. The PVWatts Version 5 manual by Aron Dobos (NLR, formerly NREL) works out the angle between the sun and the panel each hour from the surface azimuth, the sun’s azimuth, the tilt and the sun’s height.
How the sun’s azimuth changes through the day and year
Because Earth spins, the sun’s azimuth sweeps from east to west each day. Near solar noon it sits close to 180° for US homes. That is why south-facing panels usually catch the most sun.
The sweep is wider in summer. The sun rises north of east and sets north of west, so it spends more of the day on the north side of the sky.
In winter it rises south of east and stays low in the south. NOAA’s solar calculator can draw sunrise and sunset azimuth lines for any date and place.
PVWatts finds the sun’s position at the midpoint of each hour. For the 2 to 3 p.m. hour, for example, it uses 2:30 p.m., per the Version 5 manual.
The PVWatts azimuth convention
| Heading | Azimuth | What it means for panels |
|---|---|---|
| N | 0° | Faces away from the sun in the US |
| NE | 45° | Early morning only |
| E | 90° | Morning-weighted output |
| SE | 135° | Leans to morning |
| S | 180° | The PVWatts default for the northern hemisphere |
| SW | 225° | Leans to afternoon |
| W | 270° | Afternoon-weighted output |
| NW | 315° | Late afternoon only |
True north vs magnetic north
A compass needle points to magnetic north, not the geographic North Pole. NOAA calls the angle between them magnetic declination. It is positive when magnetic north is east of true north and negative when it is west. It changes with place and over time.
Across the Southeast it is negative, meaning a compass points a few degrees west of true north. That makes every compass bearing too high by the same amount. To get a true azimuth, add the declination (a negative number) to the compass reading.
The amounts are not trivial. Using NOAA’s calculator with the WMM-2025 model for 8 October 2026: Charleston, SC is about −8.3°; Atlanta, GA about −5.6°; Richmond, VA about −10.3°. Each figure carries about ±0.35° uncertainty.
Example: correcting a compass reading in three cities
Suppose you stand parallel to the gutter of each roof and your phone compass reads 180°. Here is the true azimuth after correction, using NOAA’s declination for each city.
| City | Declination 1 | Compass reads | True azimuth | What the roof really faces |
|---|---|---|---|---|
| Charleston, SC | −8.3° | 180° | 180 − 8.3 ≈ 171.7° | A bit east of south |
| Atlanta, GA | −5.6° | 180° | 180 − 5.6 ≈ 174.4° | Slightly east of south |
| Richmond, VA | −10.3° | 180° | 180 − 10.3 ≈ 169.7° | About 10° east of south |
Going the other way, a roof that faces true south shows about 188° on a compass in Charleston and about 190° in Richmond.
Enter the true value in PVWatts, since its azimuth is measured from true north 4.
A 10° error will not wreck a design, but it shifts the morning and afternoon split the model predicts.
Where azimuth shows up
On a proposal or plan set, each roof face gets an azimuth next to its tilt and panel count. Different faces mean different azimuths, and often separate inverter inputs.
In a production estimate, azimuth is a required input. Run your own check with PVWatts or our savings calculator and compare.
In shade studies, the sun’s azimuth over the year shows which trees or chimneys block light, and when. See solar shading.
Why getting azimuth right helps
Benefits of an accurate number
- More reliable kWh estimates and payback figures.
- A truer picture of morning vs afternoon output for time-of-use rates.
- Easier comparison of quotes that use the same convention.
What an error causes
- A magnetic reading entered as true can skew the morning/afternoon split.
- Mixing up "south = 0°" and "south = 180°" scales flips results entirely.
- Wrong shade timing if the sun path is drawn on a rotated roof.
Limits of the azimuth number
Azimuth alone does not predict output. Tilt, shade, weather and equipment matter as much. PVWatts notes that local weather can make the best azimuth slightly more or less than 180°.
Not every tool uses the same scale. Some older or non-US tools count south as 0°. Always check which convention a tool or quote uses before comparing numbers.
For one-axis trackers, PVWatts uses azimuth for the tracker axis, not the panel face. For two-axis trackers it does not apply.
Sources: [4]
Does azimuth change cost?
Azimuth does not change equipment prices. It changes how many kWh each panel makes, so it changes the value side: payback, savings and how many panels you need to hit a target. An east or west roof may need more panels for the same energy.
See solar payback period and cost per watt to put those numbers together.
How to measure your roof’s azimuth safely from the ground
You never need to go on the roof. These are ground-level and desk methods. Your installer will confirm the number on the site visit.
- Use aerial images first. Open a map with satellite view, line a ruler along the gutter edge, and read the bearing. Map north is true north.
- Or use a phone compass from the yard. Stand on level ground, back to the wall below the eave, and face straight out from the roof face. Keep the phone flat and away from cars, metal and electrical boxes.
- Switch the phone to true north if it has that setting. If not, correct the reading with NOAA’s declination for your ZIP code 1.
- Repeat for each roof face and write down the number with the date.
- Compare with the quote. If a face differs by more than a few degrees, ask the installer which north they used.
Roof work is fall work. OSHA requires fall protection in construction at 6 feet, and says falls are among the most common causes of serious work injuries and deaths 6. Leave the roof to crews with the right gear.
Does azimuth need upkeep?
Your roof’s true azimuth never changes. Magnetic declination does, slowly. NOAA’s model shows Charleston’s shifting about 0.05° a year, Atlanta’s about 0.06° and Richmond’s under 0.01°. For solar design that drift is negligible, but it is why you should look up the current value rather than reuse an old map.
If you use monitoring, look at when your output peaks. A roof facing a bit west peaks after solar noon. That pattern is a simple check that the azimuth on your design matches reality.
Sources: [1]
Warning signs on a quote
- Azimuth listed as 0° for a south roof, with no note on the convention used.
- All roof faces given the same azimuth on an L-shaped or hipped roof.
- A design azimuth that differs from aerial images by more than about the local declination.
- Any of these: ask the installer to confirm the convention and whether they used true north.
Safety rule
Do not climb onto a roof to take a compass or app reading. Every measurement on this page can be taken from the ground or from aerial images.
Rules and references for azimuth
No building or electrical code sets the direction panels must face. Azimuth is a design choice, limited by roof shape, setbacks and HOA rules.
The references that matter are technical. NOAA’s National Centers for Environmental Information publish declination, based on the World Magnetic Model; the current model is WMM-2025. NLR’s PVWatts defines the azimuth scale most US tools follow.
Safety rules apply to measuring: OSHA’s fall protection threshold in construction is 6 feet. For roof access rules near panels, see solar permit.
Solar azimuth vs related terms
| Term | What it measures | Changes over time? |
|---|---|---|
| Sun azimuth | Where the sun is on the horizon | Yes, every minute |
| Panel (surface) azimuth | Which way the panel faces | No, on a fixed roof |
| Solar panel orientation | The roof face choice and its effect on output | No |
| Solar panel tilt | Angle of the panel from flat | No, on a fixed roof |
| Magnetic declination | Gap between magnetic and true north | Yes, slowly |
Misconceptions
- Myth A compass gives the true azimuth.
- Reality It gives a magnetic bearing; correct it with local declination 2.
- Myth The sun is always due south at noon.
- Reality It is near south around solar noon, which rarely matches 12:00 on the clock.
- Myth Exactly 180° is always best.
- Reality PVWatts notes local weather can make the best azimuth slightly different 4.
- Myth Azimuth only matters for the sun.
- Reality It is also the main way designers describe each roof face.
Declination in SC, GA and VA
Using NOAA’s calculator (WMM-2025, 8 October 2026), declination is about 8.3° west in Charleston, 5.6° west in Atlanta and 10.3° west in Richmond 1.
So the same compass reading means a different true azimuth in each city. Virginia readings need the largest correction of the three.
Look up your own ZIP code, because declination varies across each state.
When azimuth matters to you
It matters most when you check a quote or compare two. Make sure both use 180° for south and true north. Then compare the kWh estimates.
If you are on a time-of-use rate, azimuth shifts output toward the hours you value. Read time-of-use rates and solar next.
Questions about solar azimuth
What is the best azimuth for solar panels?
In the US, about 180°, which is due south, usually gives the most energy over a year. PVWatts uses 180° as its default for the northern hemisphere. It also notes local weather can shift the best value a little either way.
Is solar azimuth measured from true north or magnetic north?
True north. NOAA and PVWatts both measure azimuth clockwise from true north. A compass reads magnetic north, so correct the reading with your local declination before using it in a design tool.
What is the magnetic declination in Charleston, SC?
About 8.3° west of true north, from NOAA’s calculator using the WMM-2025 model for October 2026. So a compass reading of 188° there is roughly true south. Declination changes slowly, so look up the current value for your ZIP code.
How do I convert a compass reading to true azimuth?
Add the local declination to the compass reading. West declinations are negative. In Richmond, VA, about −10.3°, a reading of 180° becomes about 169.7° true. Many phone compass apps can also switch to true north directly.
What is the difference between solar azimuth and solar elevation?
Azimuth is the sun’s direction along the horizon, measured from true north. Elevation is how high it is above the horizon. Together they place the sun in the sky. NOAA’s solar calculator gives both for any date and place.
Does a higher azimuth mean more afternoon power?
Yes, in the northern hemisphere. PVWatts says increasing the azimuth favours afternoon production and decreasing it favours morning production. A west-facing roof at 270° makes most of its energy later in the day.
How can I find my roof azimuth without going on the roof?
Use satellite view in a map app and read the bearing along the gutter edge, or stand in the yard facing straight out from the roof and use a phone compass set to true north. Never climb onto the roof to take a reading.
Why does my installer’s azimuth differ from my compass?
Most likely because they used true north and your compass used magnetic north. In the Southeast that gap is about 5° to 10°. Ask which reference they used. A difference much larger than the local declination is worth questioning.
Does the sun’s azimuth change through the year?
Yes. In summer the sun rises north of east and sets north of west. In winter it rises south of east and sets south of west. That shift is why shade from a tree can matter in one season and not another.
Sources
- NOAA NCEI, Magnetic Field Calculator (declination, WMM-2025) for Charleston, Atlanta and Richmond, computed 8 Oct 2026, retrieved .
- NOAA NCEI, Magnetic Declination (Variation), retrieved .
- NOAA Global Monitoring Laboratory, Solar Calculator Glossary (azimuth and elevation), retrieved .
- NLR (formerly NREL), PVWatts Calculator help: Azimuth, retrieved .
- Aron P. Dobos, PVWatts Version 5 Manual (NREL/TP-6A20-62641, 2014), retrieved .
- US OSHA, Fall Protection, retrieved .
Expert review
Written by the HyreSolar Research team. Not yet reviewed by an outside expert. We say so rather than imply a review that has not happened; see our editorial policy.
How the numbers were checked: Declination values computed with NOAA’s calculator (WMM-2025) for city-centre coordinates on 8 Oct 2026; azimuth definitions from NOAA GML and the PVWatts help text; sun-position method from the PVWatts V5 manual; fall threshold from OSHA. No production figures are given; orientation results live on the orientation page.
Suggest a correction. We fix errors and say what changed.