Cutting trees for marginal solar improvement

NoGoodAtScreenNames

Feeling the Heat
Sep 16, 2015
314
Massachusetts
On the day we had our solar panels installed we had a bad thunderstorm that damaged a tree (no danger to the panels thankfully). So that means another trip out for the tree company.

When we had our solar analysis done our solar access dips as the sun gets lower in winter and some trees start shading the roof. I just squeezed by on my solar access number to get a utility rebate. Since I’m having a tree company out anyway I’m thinking about taking two oaks down that would be the problem in the winter months. Solar company says taking them down will help (duh) but I get the feeling they always say to take the trees down

The pic below is of the roof in January at 10 AM. Do you think removing these will have a noticeable effect. As far as I could tell the roof is never in full sun during the winter. At the same time I’m thinking that there are no leaves on the trees and there would still be a decent amount of sun getting through. Plus it’s in winter and there’s a good chance that they will be covered with snow for a good number of days regardless of what I do with the trees.

What do you think?
 

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Z33

Burning Hunk
Apr 14, 2014
222
Atlanta, Georgia
Like most things in life it depends.

Do you have optimizers ?

How many KW is your system?

Do you have net metering?

I don't see the panels in your pic, is the coverage the same on the panels ?

Panel orentation ?

Do they shade a part of the house in the summer reducing HVAC loads ?

How much of the day does the shading persist?

How much of the year does the shading persist.

How much would removal be.


The saving grace is that early morning production is lack luster due to the distance and angle of the sun. If it were shaded like this at 1Pm that small amount of shading would easily cost you 50 percent of your production.

If it's an hour of shade from 9-10 I wouldn't worry too much. The cost to remove the trees will probably be more than you will ever pay back with the increased production over the life of the system.
 

peakbagger

Minister of Fire
Jul 11, 2008
5,490
Northern NH
Its very site specific. Folks do not realize how little it takes to drop panel output. A strip of electrical tape horizontal across a panel will drop the output to very low. A vertical stripe is less bad but usually the output drops by a 1/3. If you have optimizer or microinverters it only impacts one panel but string inverters without optimizers it can pull down the entire array. You have both vertical and horizontal stripes so an array on the roof would not be putting much power out. Arrays usually put out a bit more power in the AM as they are cooler.

Note there are claims by various panel manufacturers that their panels are better with diffuse light. Yes one type of panel may be slightly better but not enough to make a significant difference. Its mostly a selling tool.

Any decent solar installer has a portable analysis tool that can simulate the output over the course of the year and factor in shading ans what you show in the picture is shading.

Snow will not stay on the panels all winter. A few sunny days and the snow will slide off which is something you need to factor in with respect to landscaping and exterior doors and decks. It can build up a lot of force when it lets loose. You can have snow hooks installed but then the snow stays a lot longer. That snow will definitely dent panels on vehicle. and can hurt or kill someone If access is good, a plastic roof rake can quickly remove the snow. I do it routinely on 2 of my arrays. My third array is on second floor roof which is not fully accessible from the ground. I can get at the lower edge and if I can just get the strip of shingles below the lower edge of the panels and a foot or so of the panels, the sun will fairly quickly loosen the rest of the snow up.
 
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NoGoodAtScreenNames

Feeling the Heat
Sep 16, 2015
314
Massachusetts
Thanks. We do have optimizers and the solar company did a sky view analysis using 4 points on the roof. The trees are not an issue through most of the year, but become so in the winter months. These aren’t the only trees that cast shade but they are the ones that I have control over and seem to have the biggest impact in the 8:00 to 1:00 range. Sun sets around here at 4:30 in the dead of winter so that’s a lot of my peak hours in there.
 

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semipro

Minister of Fire
Jan 12, 2009
3,862
SW Virginia
Depending upon how and when light hits your roof you may also be able to:
  1. Oversize your array or install panels on another roof section and plan for partial shading at different times.
  2. Arrange the panels geometrically on the roof in strings to maximize power capture during partial shading.
Is topping the trees an option? Though I hate the look at first, some trees can be pruned to maintain a max height while looking good.
 

begreen

Mooderator
Staff member
Nov 18, 2005
84,163
South Puget Sound, WA
We had to make a similar call when siting our panels. There is a big redwood to the SSE of the house that casts a strong winter shadow. We decided to leave it and locate the panels off the house. In spite of the bigger cost, trees provide shade and cooling in the yard and food and habitat for many creatures.
 

NoGoodAtScreenNames

Feeling the Heat
Sep 16, 2015
314
Massachusetts
At this point I’m probably leaning against removal. Here’s my thinking.
- Although my production will dip in the winter, my daytime demand also dips
- My net metering is not very generous so there’s not much incentive to increase production past what I use during the day. In the winter my heavy loads are after sunset - laundry, electric stove / oven, car charging.
- I can probably find a better use for the tree money to other efficiency things around the house
 

Highbeam

Minister of Fire
Dec 28, 2006
17,619
Mt. Rainier Foothills, WA
I've cut a lot of trees away from my home. Never regretted it. Trees near enough to cast shadows also drop leaves into your gutters, branches onto your roof, of when winds get up over 80 mph cause the wife to worry. They burned really well in the stove.

Trees are a nice thing to see in the distance.
 

begreen

Mooderator
Staff member
Nov 18, 2005
84,163
South Puget Sound, WA
Never had a branch land on the roof and we have stainless gutter screens to keep out the debris. They are pretty effective. Now moss on the roof, that is another issue.
 

ABMax24

Feeling the Heat
If you care about solar production at all cut them down. Given that picture you have I'd say you'll be at less than 30% of what you should be for un-shaded output during the winter. All you have to do is partially shade one cell on the panel to cut power output in half. Even microvinverters or optimizers can't solve that problem you have. Given that picture I'd say at least one cell on every panel will be shaded, but in reality a sizable number of cells on each panel will be shaded.
 

begreen

Mooderator
Staff member
Nov 18, 2005
84,163
South Puget Sound, WA
If the house is the only option for mounting, then that may be what is required on the south side. Maybe replace them with trees that provide good shading without getting too tall. We love our apricot trees on hot summer days. They create a great canopy where it's often 5º cooler under it. I only have an autumn shot. These trees stay under 20ft tall.

autumn-chairs.jpg
 
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Woodsplitter67

Minister of Fire
Jan 19, 2017
1,382
Woolwich nj
I did top my trees last year for the same reason, winter production got some shade from the trees. I really didn't see much of a difference in production afterwards.. winter production sucks anyway short duration and low angle. production isn't great. I thing taking them down my be counter productive.. topping may get you a little production.. i didn't take mind down as my summer production is high.. Last month was 2.555 Mw produced and I'm basically covering my yearly usage. taking the trees down means my house bakes in the summer creating more usage keeping the house cool. Me.. Im mostly concerned with spring,summer ,fall production.. this is where I build my credit and cover the winter month usage and lower production
Screenshot_20200701-084549_Samsung Internet.jpg
 

peakbagger

Minister of Fire
Jul 11, 2008
5,490
Northern NH
Opening up the solar window to maximize winter power production was an off grid trick back when panels were very expensive. When someone paid $10 bucks a watt they wanted to get every watthour they could as the alternative was the generator or candles. Folks used to mount panels on the tops of tall trees to get sun (and hope they didnt attract lightning)Off gridders tend to garden a lot so they wanted large gardens with sun from sunrise to sunset so it made sense to cut a swath of trees for the garden and the panel. With cheap panels, net metering and grid connected systems cutting trees is far less important.

On the other hand I saw a bunch of Vivent ( a large solar firm) installs in mass where a large amount of the solar coverage was under large oak trees. I have no doubt that these systems didnt meet the predicted producution.
 

begreen

Mooderator
Staff member
Nov 18, 2005
84,163
South Puget Sound, WA
I did top my trees last year for the same reason, winter production got some shade from the trees. I really didn't see much of a difference in production afterwards.. winter production sucks anyway short duration and low angle. production isn't great. I thing taking them down my be counter productive.. topping may get you a little production.. i didn't take mind down as my summer production is high.. Last month was 2.555 Mw produced and I'm basically covering my yearly usage. taking the trees down means my house bakes in the summer creating more usage keeping the house cool. Me.. Im mostly concerned with spring,summer ,fall production.. this is where I build my credit and cover the winter month usage and lower production
View attachment 261777
Our winter production sucks too. It's spring through fall that we count on.
 

Woodsplitter67

Minister of Fire
Jan 19, 2017
1,382
Woolwich nj
Our winter production sucks too. It's spring through fall that we count on.
I understand where he's coming from wanting to maximize the production... As we all have found out.. winters just a dead zone..not much we can do about that as a species yet..
 

semipro

Minister of Fire
Jan 12, 2009
3,862
SW Virginia
As we all have found out.. winters just a dead zone..not much we can do about that as a species yet..
Most of us are here at this site because we take advantage of the solar power stored in trees to heat our homes. ;)
I get what you're saying though and I'll get to experience the dead zone on our new PV system this winter for the first time.
 

Woodsplitter67

Minister of Fire
Jan 19, 2017
1,382
Woolwich nj
Most of us are here at this site because we take advantage of the solar power stored in trees to heat our homes. ;)
I get what you're saying though and I'll get to experience the dead zone on our new PV system this winter for the first time.
what size system did u install,are you ground mount or roof mount. Tell us a little anot the system..
 

begreen

Mooderator
Staff member
Nov 18, 2005
84,163
South Puget Sound, WA
We have two arrays. One rack mounted and the other on a pole. The pole-mounted array is aligned to the SW to extend late afternoon and evening summer sun.
 

semipro

Minister of Fire
Jan 12, 2009
3,862
SW Virginia

maple1

Minister of Fire
Sep 15, 2011
10,546
Nova Scotia
I've cut a lot of trees away from my home. Never regretted it. Trees near enough to cast shadows also drop leaves into your gutters, branches onto your roof, of when winds get up over 80 mph cause the wife to worry. They burned really well in the stove.

Trees are a nice thing to see in the distance.
Went through that at our cottage the past 3 or so years. Very big maples.

First go round was 2017, before we actually owned it. Was close family for decades, then ended up in his estate in 2017 before we took the plunge on it. He had been thinking about doing something with them for years but never got to it. They were always dropping bits of limbs (one knocked the service line down the winter before), and the cottage was always cold & damp. A big threat to other power lines & close neighbors too. The worst 7 got taken down then. Which revealed a lot of really big limbs were going bad inside. So very good thing to get done. Still left 2 on each side out front where the power lines were. Got on the power co a month before Dorian came through last fall. They got a crew out, finally, to take down 3 of those 4 the day before Dorian. The one they left, they said, wasn't close enough to the lines for their contract to cover. (Like, 12' instead of 10'). It came down in the storm, on our cottage. Was only a glancing blow, only knocked a section of gutter out of place. Got real lucky there. Not sorry at all to have them gone, and the neighbors even more so. Still have a couple out back, but almost right on the property line and the neighbors there like them there so leaving for now. We each have sheds under them, and I think they would reach either cottage. Kind of shudder when I sit & look at them.
 
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SpaceBus

Minister of Fire
Nov 18, 2018
4,546
Downeast Maine
I've cut a lot of trees away from my home. Never regretted it. Trees near enough to cast shadows also drop leaves into your gutters, branches onto your roof, of when winds get up over 80 mph cause the wife to worry. They burned really well in the stove.

Trees are a nice thing to see in the distance.
After much reluctance, my wife agreed to cut several trees around the house. Life is much better now.
 

Highbeam

Minister of Fire
Dec 28, 2006
17,619
Mt. Rainier Foothills, WA
Oh and septic, I have seen too many septic and sewer lines ruined by tree roots. Not all tree roots seek the nutrients and moisture so aggressively but some sure do.

Oh and foundations, too close and it will heave.

I like trees. Like to burn them, grow them, but just a safe distance from the home. 1.5 tree lengths from the home is the normal limit for safety.
 
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begreen

Mooderator
Staff member
Nov 18, 2005
84,163
South Puget Sound, WA
Oh and septic, I have seen too many septic and sewer lines ruined by tree roots. Not all tree roots seek the nutrients and moisture so aggressively but some sure do.

Oh and foundations, too close and it will heave.

I like trees. Like to burn them, grow them, but just a safe distance from the home. 1.5 tree lengths from the home is the normal limit for safety.
Make that 10 or 20 tree lengths if elm. They travel underground incredible distances. Nice for hedgerows out in the fields, but not near a house. Similar story for willow. They both like septic systems.
 
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semipro

Minister of Fire
Jan 12, 2009
3,862
SW Virginia
Wow. I guess we've been lucky so far. We have some 50+ ft. maples located no more than 20 ft. south from our house with poured concrete basement walls. Thus far no problems.
Of course, we've also been able to forgo AC for many years where most that live nearby use it.
Tree roots are amazing though. I recall someone working on the cancelled supercollider project in Texas telling me that they found Mesquite roots at a depth of 200 ft. when they were doing borings in Central Texas.
 

maple1

Minister of Fire
Sep 15, 2011
10,546
Nova Scotia
Oh and septic, I have seen too many septic and sewer lines ruined by tree roots. Not all tree roots seek the nutrients and moisture so aggressively but some sure do.

Oh and foundations, too close and it will heave.

I like trees. Like to burn them, grow them, but just a safe distance from the home. 1.5 tree lengths from the home is the normal limit for safety.
You keep bringing stuff up I can directly relate to. That was another thing at our cottage. Crude sketch shows the line going from tank to unknown type of field, right between 2 of what is now big butt maple stumps only maybe 12' apart. It's a very lightly used system, but I was also way leery about what the roots looked like under there. But at least they're not growing any more. Shudder to think what we'd be in for if the septic malfunctioned, at that place.

There are all kinds of other places out there that are in for a world of hurt if a storm brings a tree down in the wrong direction. Places on top of one another, with lots of really big trees scattered around.
 
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