Most solar guides tell you to face panels south and leave it at that. But “south” means different things depending on whether you are using a phone compass (magnetic south) or a satellite map (true south) — and in some US states the difference is up to 20 degrees. This guide shows you how to find your exact panel azimuth, correct for magnetic declination, and calculate solar declination for any date — all free, no account needed.
Start with the calculator below to get your corrected true azimuth, magnetic declination, and solar declination in one step.
Azimuth & Solar Declination Calculator
Enter your location and date to get your corrected compass bearing for true south
Calculating azimuth and declination…
Magnetic declination calculated using the simplified NOAA IGRF formula (accurate to within 1 degree for most US locations). Solar declination uses the Spencer formula. For precise scientific applications use the official NOAA Solar Position Calculator at ngdc.noaa.gov.
Azimuth vs Declination — Three Terms Most People Confuse
When researching solar panel orientation, you will encounter three terms that sound similar but measure completely different things. Mixing them up leads to panels aimed at the wrong direction or tilted at the wrong angle. Here is exactly what each term means:
What Is Solar Panel Azimuth? (And Why 180 Degrees = True South in the US)
Azimuth is simply the compass bearing of your panel’s face — the direction it “looks at.” In the Northern Hemisphere, the sun always arcs through the southern sky, so panels facing true south (180 degrees) collect the most light over an average day. Here is how the full compass translates to panel performance:
A deviation of 10 to 15 degrees from true south costs only 1 to 2% of annual output. A 30-degree deviation costs about 5%. Panels facing east or west (90 or 270 degrees) lose roughly 15 to 20% compared to true south — but west-facing panels can be financially better in states like California where afternoon electricity rates are significantly higher.
Magnetic Declination vs Solar Declination — Not the Same Thing
This is the single biggest source of confusion in solar orientation guides. The word “declination” appears in two completely unrelated solar contexts:
| Property | Magnetic Declination | Solar Declination |
|---|---|---|
| What it measures | Error between magnetic north and true north | Sun’s angular position above or below the equator |
| Changes with | Your geographic location | The date (changes daily throughout the year) |
| US range | -20 deg (Pacific NW) to +20 deg (New England) | -23.5 deg (Dec 21) to +23.5 deg (Jun 21) |
| Who uses it | Anyone using a physical or phone compass | System designers optimizing seasonal tilt |
| Where to find it | NOAA Magnetic Declination calculator or calculator above | NOAA Solar Position Calculator or calculator above |
| Effect on panels | Corrects your compass bearing for true south | Determines optimal seasonal tilt angle adjustment |
How to Find Your Panel Azimuth Using Google Maps — 4 Steps
You do not need expensive equipment to measure your panel azimuth accurately. Google Maps uses true north (not magnetic north), so any angle you measure on the satellite view is already a true azimuth — no declination correction needed. This method takes about 5 minutes and is accurate to within 2 to 3 degrees for most installations.
| Method | Accuracy | Equipment | Time |
|---|---|---|---|
| Google Maps + protractor | Within 2 to 3 degrees | Free (browser + screenshot) | 5 minutes |
| Phone compass (uncorrected) | Within 5 to 20 degrees (varies by state) | Phone compass app | 2 minutes |
| Phone compass + magnetic declination correction | Within 1 to 2 degrees | Phone + NOAA correction | 5 minutes |
| Physical digital protractor tool | Within 1 degree | Digital protractor ($15 to $30) | 10 minutes on-roof |
True North vs Magnetic North — Why Your Compass Points the Wrong Way
Your phone compass does not point to the geographic North Pole — it points to the magnetic North Pole, which is currently located in northern Canada and drifts slowly each year. The angle between magnetic north and true north at your location is called magnetic declination, and in parts of the US it reaches 20 degrees — enough to meaningfully reduce your panel output if uncorrected.
Here is how magnetic declination varies across key US states and what correction your compass needs:
| State | Magnetic Declination | Direction | Compass Reading for True South |
|---|---|---|---|
| Washington | +15 to +17 deg | Magnetic N is east of true N | 163 to 165 deg |
| Oregon | +13 to +15 deg | Magnetic N is east of true N | 165 to 167 deg |
| California | +10 to +13 deg | Magnetic N is east of true N | 167 to 170 deg |
| Texas | +3 to +6 deg | Small eastward offset | 174 to 177 deg |
| Illinois / Ohio | 0 to -2 deg | Near zero — minimal correction | 180 to 182 deg |
| Florida | -5 to -7 deg | Magnetic N is west of true N | 183 to 185 deg |
| New York | -13 to -14 deg | Magnetic N is west of true N | 193 to 194 deg |
| Maine | -16 to -18 deg | Largest eastward error in lower 48 | 196 to 198 deg |
NOAA Solar Position Calculator — How to Use It for Free
The NOAA Solar Position Calculator (available free at gml.noaa.gov/grad/solcalc) is the most authoritative free tool for finding your solar azimuth, solar zenith angle, and solar declination for any location and date in the world. It is maintained by the US National Oceanic and Atmospheric Administration and uses the same algorithms that professionals use for solar system design.
Here is what each NOAA output means for your solar panel placement decision:
Best Azimuth for Solar Panels by US Region
True south (180 degrees) is the optimal azimuth for maximum annual energy production at every location in the continental US. But roof constraints, shading, and utility rate structures sometimes make a slightly east or west facing panel more practical — or even more financially rewarding. Here is how deviation from true south affects your output:
| US Region | Optimal Azimuth | TOU Rate Consideration | Notes |
|---|---|---|---|
| Southwest (AZ, NV, NM) | 180 deg (true south) | 240-250 deg if on TOU peak plan | High irradiance — small deviation = small loss |
| California | 175-185 deg | 240-270 deg (NEM 3.0 favors afternoon) | Under NEM 3.0, west-facing can earn more bill savings |
| Pacific Northwest (WA, OR) | 180 deg (true south) | Not significant — flat rate common | Maximize kWh production due to lower irradiance |
| Texas | 175-185 deg | 250-270 deg if on ERCOT TOU plan | Afternoon peak rates high in summer — west angle helps |
| Southeast (FL, GA, SC) | 180 deg (true south) | Not significant | Low magnetic declination — raw compass nearly correct |
| Northeast (NY, MA, CT) | 180 deg (true south) | 200-210 deg slight west helps | High magnetic declination — always apply correction |
| Midwest (IL, OH, MI) | 178-182 deg | Not significant | Near-zero declination — compass nearly matches true south |
The one major exception to true-south-is-best is California under NEM 3.0 (effective April 2023). The new net metering structure pays significantly higher export credits for power exported during the late afternoon peak (4 to 9 PM), making west-facing panels at 240 to 270 degrees a better financial choice for many California homeowners — even though they produce fewer total kWh per year than south-facing panels.
Frequently Asked Questions
Quick answers to the most common azimuth and declination questions from US solar owners and installers.
What is the best azimuth angle for solar panels in the US?
True south (180 degrees) gives maximum annual energy production at every location in the continental US. Deviating 15 degrees costs only 1 to 2% of annual output. The exception is California under NEM 3.0, where west-facing panels at 240 to 270 degrees can earn more in bill savings due to higher afternoon export credit rates, even though they produce fewer total kWh per year.
What is the difference between magnetic declination and solar declination?
They are completely different. Magnetic declination is the angle between magnetic north and true north at your location — it corrects your compass for true south. Solar declination is the sun’s angular position above or below the equator on a given date (plus 23.5 degrees in summer, minus 23.5 in winter). Magnetic declination affects your panel direction; solar declination affects your optimal tilt angle.
How do I find my solar panel azimuth without special equipment?
Use Google Maps satellite view. Right-click your roof, select Measure Distance, draw a line parallel to your panels, then draw a line pointing north. Measure the angle between them with a free online protractor. Because Google Maps uses true north, the reading is already your true azimuth — no declination correction needed. Typical south-facing US roofs read 160 to 175 degrees.
How do I use the NOAA Solar Position Calculator for my panels?
Go to gml.noaa.gov/grad/solcalc and enter your latitude, longitude, and today’s date at 12:00 PM local time. The results show your solar azimuth (sun direction at noon, close to 180 degrees for US locations), solar elevation (for shading checks), and solar declination (for seasonal tilt adjustment). Cross-check the solar azimuth reading with your Google Maps panel measurement to verify both are consistent.
Why does my phone compass give a different direction than Google Maps for true south?
Your phone compass points to magnetic north, not true north. Google Maps always uses true north. The difference is your local magnetic declination, ranging from minus 18 degrees in Maine to plus 17 degrees in Washington state. To convert: True Azimuth = Magnetic Azimuth + Magnetic Declination. The Azimuth Calculator at the top of this page does this automatically for your coordinates.