Is seasonal tilt adjustment worth it for residential solar?

laurajones · May 20

Most people set their panels and forget them, but if your panels are manually adjustable, changing the angle by season (or even monthly) can add noticeable gains.

According to studies, seasonal adjustments can increase annual production by up to 8%.

If you're curious what angles to use, I recommend checking SolarSCalculator. It gives you specific angles based on your location — more accurate than just using your latitude.

SumPower · May 21

With as cheep as solar panels have gotten in the last couple of years, I am now in the set it to your latitude camp. And at my age I would probably forget needing to make seasonal adjustments anyway.

So set once and forget it is a good combination.

BB. · May 21

To be honest, on a residential solar system, it is difficult to measure an 8% change in output due to change in tilt (over days/months/year) without a reference cell/almost lab grade measurement equipment.

More or less, with an off grid solar power system, you almost need 2x the "predicted power harvest/energy" to support changes in weather, dust on panels, aging (most spec. 20% drop in output over 20+ year life, etc. and minimize things like backup generator runtime.

The amount of "over sizing" your solar array also depends on your power needs/expectations and even your local conditions--Trees grow, neighbor adds on a new room/floor, etc. Even things like shading from power lines/chimney,etc. on a solar array can sometimes cut harvest by 50% while shading is present.

Looking at harvest using PV Watts for Bucharest Romania and 45 degree panel tilt:

https://pvwatts.nrel.gov/pvwatts.php

Image: https://us.v-cdn.net/6024911/uploads/editor/nm/a78ex3ry3xt3.png

Between July and December, your harvest is 3.5 more in in summer, vs dead of winter (not even accounting for low sun angle, shading from trees, snow on array, etc.).

Just for fun, same setup except now full 2 axis tracking:

Can dramatically increase harvest--But still poor harvest for December (I suggest that any sun less than ~3 hours of harvest per day is "not great" for solar).

-Bill

JRHill · May 21

My roof is a 10/12 pitch where the panels are located and they are parallel to the roof. I made my rails with the ability to adjust the angle. In 15 years I've never climbed up on the roof to do it. After a short time I realized that when I really could use every little bit on harvest to be gained by changing the pitch it isn't worth the effort because the yield is so low with heavily clouded skies in the winter season. In fact I could quadruple the amount of panels and it still wouldn't be enough to keep me from running the genset to charge batteries.

Come the summer solstice the panels are further off optimum than in the winter. But with the longer days and clear skies the system is in float by 1pm even with much greater power consumption. In the summer I have no way to take advantage of the wasted potential.

I guess we just live in the wrong place. OTOH there are no tornados or floods and electrical storms are rare. I would actually appreciate more blizzards but that is about every 5 years.

Ralph Day · May 22

With my house system 2.1kw, I just change the angle in spring and fall. It got to be too much to do every month. My FIT (micro fit in Ontario) I can chang the angles in about 5 minutes, if there's no wind. Well engineered, pivots greased etc. That I do monthly. Probably worth it for increased yield as my time is not worth much or much taken. Only 5 years left on the contract. I wonder what will happen when that runs out? About 16,000kw per year produced. I only use about 2000kw per year, so might have to change from wood heat to all electric

And buy a few electric cars and trucks.

Is seasonal tilt adjustment worth it for residential solar?

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