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The optimum solar panel angle to maximize power output depends on the system geophysical location and the season. In Summer the angle can be calculated by subtracting 15° from the location latitude and in the Winter by adding 15° to the latitude. Seasonal angle adjustment can increase annual power output by up to 15%.
Why are solar panels installed at an angle?
Solar panel output is affected by several variables, some we can adjust and others are decided by our location and environment.
One way to make sure you’re optimizing the power output of a solar panel array is to adjust the tilt angle. Solar cells are most efficient when the sun’s rays are perpendicular (90°) to the panel surface.
The optimum tilt angle will vary according to location and the effect on solar output will be variable according to the irradiation level at your geophysical location.
Video – Optimum Title Angles For Solar Panels
What is the optimum solar panel angle?
Contrary to popular belief, power output due to tilt angle isn’t caused by the structure of the solar cells, but simply the fact that the sun’s energy is spread over a greater area when the angle is oblique.
Checkout the image below:
If the sun’s rays cover 1 square meter of the panel surface at 90°, then the same sun’s energy will be spread over 1.5 square meter if the panels is tilted at an angle of 45°.
What is the minimum angle for solar panels?
There really is no minimum angle for solar panel tilt. The fact is that they will still work even at 0° or at 90°. Solar panels mounted on a flat roof would be at 0°, while panels mounted on the side of a building would be at 90°.
The reduction in power output isn’t linear according to the tilt angle, because the combination of reflection and indirect sunlight generates power as well.
Is it worth tilting solar panels?
The amount of tilt angle recommended for your solar panel array depends on your geophysical location, but it’s a bit more complicated than that!
The table below shows the difference in the sun’s energy falling onto a flat panel surface compared to a panel mounted at a tilt angle of 50° in Denver Colorado.
In Denver, the amount of sun’s energy falling onto a flat solar panel is almost 50% of that irradiating a panel mounted at 50°. That’s quite a reduction.
However, in high summer, the amount of energy falling onto the flat mounted panels is more than the tilted panel. This means that the annual irradiance should be taken into account before deciding on tilt angle.
Table – Solar irradiance in Denver Colorado – 50° tilt compared to flat (0°)
Insolation by month for Denver Colorado by month (kWh/m2/day - also are known as Peak-Sun-Hours)
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Flat
2.41
3.27
4.49
5.42
6.28
6.70
6.35
5.68
5.03
3.90
2.67
2.18
50 °
4.27
4.85
5.58
5.62
5.81
5.90
5.72
5.60
5.87
5.60
4.52
4.12
If we add the irradiance in kWh/m2 (peak-sun-hours) for flat mounted panels and 50° in Denver Co, we get:
Flat mounted panels (0°) peak-sun-hours Denver = 53.81 kWh/m2 (peak-sun-hours)
50° mounted panels peak-sun-hours Denver = 75.94 kWh/m2 (peak-sun-hours)
So for Denver solar panels, if the array is mounted at a fixed angle of 50°, there is an increase in power output of about 30%.
Resource data: Global Solar Atlas
Can solar panels be laid flat?
Although irradiance is measured in direct radiation, the combination of diffused and reflected sunlight ensures that the energy generated on solar panels mounted flat is not a lot less than when at an angle.
The table below gives the average estimated reduction in output power for a solar panel array at various tilt angles in Northern and Southern USA.
Note: There will also be considerable variation from East to West. For this reason it’s best to get accurate estimates from solar professionals for your exact location and orientation.
Table – Compare solar panel ouput – tilt angle vs flat
Tilt angle in degrees
Percentage increase in production - Southern USA
Percentage increase in production - Northern USA
Flat
Assume 100 comparison only
10
108 - 8% increase
109 - 9% increase
20
113 - 13% increase
115 - 15% increase
30
115 - 14% increase
118 - 18% increase
40
114 - 14% increase
117 - 17% increase
50
110 - 10% increase
116 - 16% increase
Resource data: Solar Electrical Handbook – Solar Angle Calculator
How do I set the angle on my solar panels?
While it is possible to add an automatic motorized system to move the solar panels so that they are always perpendicular to the sun’s rays, such systems are expensive. (Sun tracking.)
It may be more cost-effective to set the solar panels angle on a movable frame and adjust the tilt angle just twice a year, summer and winter.
This would entail going up on the roof and physically changing the tilt angle, but what is the best tilt angle for you solar panel array to optimize power output?
How do you calculate the tilt angle of a solar panel?
Solar panel efficiency depends on:
As a general rule, the angle should be adjusted twice a year. Take your latitude and add 15 degrees in Winter and subtract 15 degrees in Summer.
There are resources indicating solar panel angle by zip code, but this approach is much too granular to make any meaningful gains in power output.
Example:
The latitude of Denver Colorado is 39.74, so tilt angle for summer/winter becomes:
Solar panels angle in summer = 39.74 – 15 = 24.74°
Solar panels angle in winter = 39.74 + 15 = 54.74°
It makes sense. In summer the sun is higher in the sky, so the panels need to flatter. In winter, the sun is low on the horizon and so the solar panels should be adjust to be more upright, closer to 90°.
Solar Panel Orientation
Orientation means the direction in which solar panels point. This is just as important as the panel tilt angle and should be optimized for maximum power generation.
In which direction should install the solar panel?
This depends on the which hemisphere of our planet you live on. In the Southern hemisphere, an array should point due North, while in the Northern hemisphere panels should point due South.
However, it isn’t a disaster if this can’t be done – read on.
Should solar panels face east or west?
Many roofs don’t face exactly South (Northern hemisphere), but often face South-East or South-West. These orientations are OK.
A complex roof on a larger property may have roof extensions facing in more than one direction. In this case, it’s perfectly acceptable to have a West or East orientation.
Do solar panels need to be south facing?
In the Northern hemisphere due south is perfect, but if this can’t be achieved, any variation South combined with East/West will be OK.
Irradiation comes not only directly, but also in a diffused form caused by reflection from particles in the atmosphere. This means that there is always indirect sunlight to generate some solar power.
Modern solar systems tend to have microinverters mounted per panel, or for a group of panels.
Microinverters can optimize power output of solar panel arrays with different orientations so that differences in output of one array doesn’t reduce the whole system output.
The only direction to avoid if at all possible is due North, which means the solar panels would never see direct sunlight – not ideal!
The best solar panel angle depends on your location
Solar Panel Direction and Angle – Solar Tracking
Solar panels can be adjusted in two directions; tilting up and down or side to side.
The ideal situation would be for the solar panel surface to be always at 90° to the sun’s rays. This can be achieved by mounting the panels on a mechanical apparatus called a Solar Tracking System.
This kind of automatic setup senses the sun’s location and tracks it across the sky, thus optimizing the power output.
What is a dual axis solar tracking system?
During the day the sun moves across the sky in the form of an arc, rising in the East and setting in the West. An arc has a vertical and a horizontal axis.
A Dual Axis Solar Tracker moves in both axes and is more or less always holding the panels perpendicular to the sun’s rays.
How much more efficient is solar tracking?
Solar tracking can produce up to 40% more solar power than fixed solar panels.
Sun tracking design research PDF Courtesy: North Arizona University
Are solar axis trackers worth the additional investment?
To work this out we need to know:
A solar tracker will cost around 30% of the total cost of fixed solar panels, which averages out in the USA at $3 per watt.
The average home solar power system in America is 5kW, so the capital cost would be $15000.
The cost of an auto sun tracker will be about $5000.
Annual energy produced by 5000W fixed solar panels
I’ll choose the location South Bend, Indiana, so we can use a realistic irradiance value for calculating energy generated.
GlobalSolarAtlas is a very useful database of solar irradiation by location. If we enter South Bend we find that the sun’s energy level for this location is 1422 peak-sun-hours.
1422 x 5000W = 7110 kilowatt-hours
Annual energy produced by 5000W sun-tracker
Power gains of up to 65% are claimed by some sources, but this seems a bit over the top to me. It’s best ot be a little conservative when estimating solar power output, so I’ll say you can get a solid 30% more power than with a fixed panel array.
So the dual axis solar tracker system will generate 2133 kWh more power than fixed panels.
Electricity cost per kWh
In Indiana the electricity cost per kWh is 10.53¢.
Solar Tracker Cost Analysis Calculation
Example: 5 kW solar panel system
Location: South Bend, Indiana
Fixed solar panels:
Dual Axis Sun-tracker:
In the example above the payback time is a little longer, but after the payback time the electricity is free.
The above example doesn’t account for maintenance costs of the of the solar-tracker. Any system with working parts will have maintenance costs associated with it’s operation.
Resources relating to finding the Optimum Solar Panel Angle: