Forum Discussion

ajriding's avatar
ajriding
Explorer II
Aug 30, 2019

Tilting Solar Panel

I did a little experiment.

I have a new poly 100 watt panel. Before installing

I tilted the panel to face directly into the sun. 19.6 volts.

I tilted it the same angle, but away from the sun, so at a very bad angle to still have sun hit it. 18.4 volts, was not that less of a tilt to be 19.6 (1 volt less).

I tilted it to be in the shade, only ambient light. 17.x volts.

I don't feel so bad that the panels lay flat on the roof. The bad angle was about 5% less volts. Shade was 6.x% less volts.

The controller will drop the voltage down to 14 or so, but amps will still be lower, probably 5% too.

5-6% is not bad for being able to just lay the panels flat. I see RVers with rigs where they can angle the panels perfectly and get that 5%, maybe they need it.

Am I missing something?
  • If you have room on the roof just add another panel or two. Chasing the sun with tilting would be a pain in the butt unless maybe you're using a ground deployed system and looking to do something during the day.

    With 1,280w flat mounted,
    Nov/ Dec will average 6-750w peak or 2.5-3 kwh +/- daily.
    Jan/ Feb average 7-800w peak or 3.1-3.7 kwh.
    Mar-Oct average 8-1,150w or 3-7 kwh daily.
  • Itinerant1 wrote:
    If you have room on the roof just add another panel or two. Chasing the sun with tilting would be a pain in the butt unless maybe you're using a ground deployed system and looking to do something during the day.

    With 1,280w flat mounted,
    Nov/ Dec will average 6-750w peak or 2.5-3 kwh +/- daily.
    Jan/ Feb average 7-800w peak or 3.1-3.7 kwh.
    Mar-Oct average 8-1,150w or 3-7 kwh daily.


    With a ground tilted twirler, you only need to move it three times a day to get almost as much as a continuous twirl. After sunset to SE so it is ready in the morning before you get up, to S mid-morning, and to SW mid -afternoon.

    You can just twirl it whenever you are going by the rig anyway, no special trips watching the clock needed. If you will be away all day, just aim it S before you leave in the morning.

    People with a small portable set have been seen with the panel on a chair tilted, and they turn the chair toward the sun every so often. that gets the most from their solar.

    It is all situational what is "worth it". It is easier if you are on a trip moving often, to have it all flat on the roof, and you don't have to park a certain way wrt the sun with the panels flat. (With a twirler same thing, but fixed tilt on roof you need to park so they aim South)

    Stick house roof panels are tilted with the roof, and good luck if your roof ridge is E-W. Don't buy a house that is lined up N-S if you want solar on the roof!
  • profdant139 wrote:
    Interesting discussion! I wonder why home solar panels aren't built to track the sun -- they are almost always stationary. My guess is that the cost and maintenance of tracking outweigh the gain in extra power.


    if the panels are facing south, and your in most of the U.S. normal roof pitch of 4/12 to 6/12 gives a pretty good angle to start with, so there isn't much to be gained. And if the panels are layed out to tilt very much you need to take into account a shadow of a lower panel on an upper panel. So in some cases, panel spacing needs to increase which decreases the number of panels so there is little advantage, possibly actually a loss.

    Large arrays where area is not a big limitation often do have trackers.

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