Does it matter if my solar panels face South or "True South"?

Published on January 15, 2008 by Dave Llorens.
Categories: Solar Technology.

Solar Power should Point True South

So, what is the difference between “True South” and “Magnetic South,” anyway? Well, if you imagine the axis that the earth rotates around, the point at which that pokes out of the earth in the middle of Antarctica, that’s true south. But when you hold up a compass you aren’t really finding “true” north or south, you can only find “magnetic south,” which is the direction towards the south pole of our earth’s geomagnetic field. Believe it or not, this point actually moves a few miles each year because the molten metal in the earth sloshes around.

YOU: “Dave, I think I know south is the best way to orient my solar panels (or north if you happen to live in the southern hemisphere), but do I want to face them magnetic south or true south??”

DAVE: TRUE SOUTH. We’re not concerned with the magnetic poles, just where the sun is.

YOU: “Well that’s great and all Dave, but my compass only shows me magnetic south, how the hell am I supposed to find True South? ”

DAVE: Settle down, it’s gonna be ok. There are a few ways, but the most accurate is to find the magnetic declination in your area. (Australia, Canada, US, World). For example, I can tell from these sites that in San Francisco my current magnetic declination is (14° 33′ E). Since that number is positive, I add about 14 degrees to get true south. So if my compass points to south at 180 degrees, TRUE SOUTH is about 194 degrees. Point your panels in that direction!

TIPS: Don’t have a compass? Here’s a simple old school way. When the sun is at its highest point in the sky “solar noon,” any shadow cast by a telephone pole or some other perfectly vertical object will run perfect TRUE north-south.

When taking a compass reading, never hold the compass near metal, as it will throw off your reading. Watch out for your belt buckle!

Comment on January 17th, 2008.

Good information here, lets just hope when pointing the panels 194 degrees (true south) there are nothing shading the area.

-Deep Patel
http://www.gogreensolar.com

doug Whillans Identicon Icon doug Whillans
Comment on September 11th, 2008.

Good Morning my magnetic declination in the Toronto,Ontario Canada area is 10 degrees 20′ west if magnetic south is 180 which way and how far do I move to find true south

Comment on September 11th, 2008.

So you would subtract about 10 degrees from your compass so that true south is around 170 Doug.

http://geomag.nrcan.gc.ca/apps/mdcal_e.php?Year=2008&Month=9&Day=11&Lat=43&Min=39&LatSign=1&Long=79&Min2=23&LongSign=-1&Submit=Calculate+magnetic+declination&CityIndex=247

Charlie Identicon Icon Charlie
Comment on April 13th, 2009.

The answers are a bit misleading. For Example #1 in California, You would point the compass at 194 degrees but orient your panels at the S that is still fixed on the compass.
Or you could point the needle North-South and face the panels at 166 degrees on the compass.

Kevin Identicon Icon Kevin
Comment on August 17th, 2009.

Hey Guys, You are all technically correct in the abstract yet more considerations must be made. If your area is typically foggy or cloudy in the morning, you are better off facing the panels slightly W of S to maximize gain during the afternoon. Likewise with shading, which you want to avoid at all costs, but if you have some WxSW trees and clear skies in the morning, you are better off facing the panels E of S. Get an experienced local installer to properly evaluate your particular site.

Mike Wilhoit Identicon Icon Mike Wilhoit
Comment on January 31st, 2010.

Gentlemen,

Are there any figures on power loss as you move away from true south. My house is about 12 degrees west of true south. How bad does this hurt me.

Thanks,
Mike

Comment on February 1st, 2010.

Hey, Mike.

It’s not going to hurt you all that much. You’re going to lose a little bit of power production, but that’s not a big deal. Your roof does NOT have to face exactly South, true or not. Plenty of systems get installed on Western systems and Eastern and South Eastern etc. North, now that’s a problem.

Assuming you’ve got good subsidies, net metering, and good sun, it’s still going to be very cost effective for you. Being a few degrees off South will just mean that it will take you slightly longer for payback. Perhaps 10 years and two months, for example, instead of 10 years. It will be minor.

Hope that helps.