One big mistake people commonly make when design and setting up their own off grid or on grid solar system is to not take in to account proper panel angle. It may seem simple at first glance, but facing your panels at the wrong tilt can cost you a lot in lost power if you aren’t careful.
What angle should I face my solar panels? In the northern hemisphere, face your panels due south and 90 degrees minus your latitude from the horizon. (Due north in the southern hemisphere). This maximizes yearly average power generation. Off grid systems often benefit by tilting them up to 15 degrees up or down from this point to fit their seasonal power demand.
How Do I Determine What Angle I Should Tilt My Solar Panels
Generally, solar panel direction and placement is broken down in to two parts. Direction and tilt.
Direction is the simplest, north or south. Fixed solar panels are always most effective when they are facing due south (or due north in the southern hemisphere). This is often of most concern on roof top installations, where the walls of the house, and thus the slope of the roof not quite in the right direction. In the below graph, you can see that being only 15 to 20 degrees of can have a dramatic impact on potential production of the panels. Also, if you are going to have a single axis tracking system installed, then a direction tracking “azimuthal” or “equitorial” tracking system often gives the biggest bang for the buck.
The other concern is tilt angle. This can be represented in two ways. Degrees from straight up, that is where the face of the panel would be level. The other being degrees from the horizon, zero being where the face of the panel is plumb up and down.
On grid systems, that can sell back their excess power, or are undersized relative to the needs of the household, have an easy answer. Tilt the panels the same number degrees from level as you are above (or below) the equator. That is, tilt the panels the same as your latitude. Examples of ptimum tilt angles for some major city are listed below.
Solar Panel Tilt Angle for Off Grid Solar Systems
The best tilt angle depends a lot on your particular situation when you are building an off grid system. This is because off grid systems need to produce enough energy to keep your system going all year round. And, production generally drops off in the winter.
Thus, if you follow the general rule, you will probably have a ton of excess power generated in the summer, because you have to size your solar panel array to cover the lean times. Generally you can save money by tilting your panels down up to 15 degrees from optimum. This decreases your summer power (and total power) production, but increases the winter production, and thus usually allows you to get away with fewer panels.
If you have very heavy summer usage, however, it may be better to tilt up your panels. This is common in locations with very hot summers, where you intent to use air conditioning and or large scale refrigeration on your system
In order to make an informed decision, you need to know or calculate your seasonal off grid power usage. Read my article on calculating off grid energy needs for more information.
How Angle Affects Solar Panel Output
Solar panels work by turning light energy directly in to electrical energy. Because of this, their power output is reduced when fewer “light rays” can hit the panel because of the way it is placed. Panel orientation can have a major effect on the power output of a solar panel or array.
In the above diagram, it is easy to see why. The best position for a panel to be in is dead face on with the Sun, so that the maximum amount of light can hit the surface. Compare this to the panel right next to it, which is tilted 45 degrees to the side. This panel will be receiving only about half of the light energy as the panel beside it, and thus will produce half or less the amount of power.
For the mathematically inclined, the proportion of power available to a tilted panel is proportional to the cosine of the angle between the sun rays and the normal (a line 90 degrees from the surface) of the panel. You can also calculate this as the sine of the angle between the solar panel surface and the Sun.
Are Solar Tracking Systems Worth It?
Solar tracking systems can significantly increase the power production of a solar system, although they can come as a significant cost.
One or two axis solar tracking system can significantly increase your solar panel output over fixed systems. This is especially the case for summer production, and may increase your total yearly production by around 40%.
For on grid, undersized systems, or systems with extra heavy loads in the summer, this extra investment in tracking panels may be worth it, if the cost of the tracking system is less than the cost of an equivalent number of additional panels. Another consideration is that for panels not placed in equatorial regions, azimuthal rotating tracking systems give a very strong performance, and generally come at a reduced cost vs more complex two axis tracking setups.
DIY Panel Tracking System
One option easy is to build a manually adjusted tilting system, which can be a relatively cheap DIY project, and can net you a free %4 energy production increase if you manually move the panels four times a year. This may not seem like a lot, but you also benefit from a nice bump in power during the darkest parts of the winter, while maintaining full power output in the summer, making a little extra investment in time and ingenuity worth it many situations. (See “Effect on Solar Panel Tilt on Power Production” above).
The way I recommend constructing such a setup is to build a tilted frame for your panels, out of lumber or whatever other cheap material you have available, in the form of a right triangle. A few heavy duty hinges at the bottom corners and a selection of bolt holes along the vertical support would give you a variety of positions to adjust your panels for different total outputs during the year.
Optimum Solar Panel Tilt Angle for US and Canadian Cities
By tilting your panels as show in this table, your panels will produce the most power possible, on average. Take steps to ensue your panels have a complete unobstructed view of the sky.
Using this number directly is usually the best option for grid connected solar systems. However, if you are building an off grid system you often have excess production during certain times of the year (frequently the summer) and it is generally more cost effective to tilt your panels as much as 15 degrees down (or up in some cases) from this number to level out your production curve.
|City, State||Direction||Tilt (best average)|
|Hot Springs, Ark||South||34|
|New York, N.Y.||South||40|
|San Francisco, Calif.||South||37|
|Santa Fe, N.M.||South||35|
|Toronto, Ont., Can||South||43|
|Winnipeg, Man., Can||South||49|
Optimum Solar Panel Tilt Angle for Some Major World Cities
This table shows the optimum tilt from dead level, and the direction of this tilt, calculated for various world cities. This angle produces the highest average yearly output, assuming the solar panels have a complete unobstructed view of the sky, and is appropriate for grid connected systems.
Off grid system generally benefit from up to 15 degrees deviation in either direction from this average, in order to maximize production in heavy use or low production times of the year.
|City, Country||Direction||Tilt (best average)|
|Auckland, New Zealand||North||36|
|Cape Town, South Africa||North||33|
|Durban, South Africa||North||29|
|Johannesburg, South Africa||North||26|
|New Delhi, India||South||28|
|Wellington, New Zealand||North||41|
Why Are Solar Panels on an Angle?
Solar panels produce the most energy when they directly face the Sun. Solar arrays are generally either tilted to get the most energy from the sun near the brightest part of the day, or mounted on computerized motors that continuously face the panels directly at the Sun.
Do Solar Panels Have to be on an Angle?
Solar panels produce much more energy when facing due south, and tilted to within 15 degrees of your current latitude. Although panels positioned in other ways will still produced power, dead flat or directly on a roof for instance, in many cases this would reduce power production by as much as 50% or more, depending on the details of the situation.
What Is the Best Angle for a Solar Panel?
Fixed solar panels work best when they are directly facing south (or north in the southern hemisphere) and are tilted to within 15 degrees of your current latitude. Maximum power production is reach for fixed panels when the angle from straight up is the same as your latitude, but this is still around 40% less than you could get from a solar tracking system.