# Cutting trees for marginal solar improvement



## NoGoodAtScreenNames (Jul 21, 2020)

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 (Jul 21, 2020)

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.


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## peakbagger (Jul 22, 2020)

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 (Jul 22, 2020)

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 (Jul 22, 2020)

Depending upon how and when light hits your roof you may also be able to: 

Oversize your array or install panels on another roof section and plan for partial shading at different times.
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.


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## begreen (Jul 22, 2020)

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.


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## NoGoodAtScreenNames (Jul 22, 2020)

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


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## Highbeam (Jul 23, 2020)

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.


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## begreen (Jul 23, 2020)

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.


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## ABMax24 (Jul 23, 2020)

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.


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## begreen (Jul 23, 2020)

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.


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## Woodsplitter67 (Jul 24, 2020)

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


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## peakbagger (Jul 24, 2020)

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.


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## begreen (Jul 24, 2020)

Woodsplitter67 said:


> 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.


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## Woodsplitter67 (Jul 24, 2020)

begreen said:


> 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..


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## semipro (Jul 25, 2020)

Woodsplitter67 said:


> 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.


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## Woodsplitter67 (Jul 25, 2020)

semipro said:


> 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..


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## begreen (Jul 25, 2020)

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.


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## semipro (Jul 26, 2020)

Woodsplitter67 said:


> what size system did u install,are you ground mount or roof mount. Tell us a little anot the system..


9.5 kW with 30 panels.  In operation, the max output has been about 8.5 kW. 
Post about the project here: https://www.hearth.com/talk/threads/finally-my-solar-pv-installation.178424/
Photos of the finished system below.


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## maple1 (Jul 27, 2020)

Highbeam said:


> 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 (Jul 27, 2020)

Highbeam said:


> 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.


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## Highbeam (Jul 27, 2020)

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 (Jul 27, 2020)

Highbeam said:


> 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 (Jul 27, 2020)

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.


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## maple1 (Jul 27, 2020)

Highbeam said:


> 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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## NoGoodAtScreenNames (Aug 11, 2020)

I’ve been trying to read up a little more on the impact of shading. When we made the decision to go solar it was based on the trees being there. I found a white paper for my panels Solaria Power XT that analyzes the impact of different types of shading. Granted, these are lab tests but it is interesting to see it cover some of the prior comments about not just the percentage of shade but it’s direction too being important. 

The multi path flow in the panels deals with shading better that a snake an up down and over pattern.The exception would be the straight vertical where the panels under perform vs. the more traditional orientation.



			https://static1.squarespace.com/static/568f7df70e4c112f75e6c82b/t/5ebad31ca375f52b5424f27d/1589302053132/shading-whitepaper_Rev-02.pdf
		


So those vertical trunk shades will be problematic. My arrays are oriented left half / right half. One goes through each of the arrays, so I’m back on the fence and may take down after all...

Oh and here’s how the panels look on the roof. The shading is from early morning when the sun is just getting over the trees.


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## semipro (Aug 11, 2020)

It seems to me that the real question is whether your annual production and net metering will cover your annual usage.  If it does, don't sweat the shading.
Net metering in Virginia is rolled over annually so we're hoping to build up enough banked kwh in the summer to carry us through the winter. 
I realize your net metering may be different. 
PS- I appreciate the geekiness of looking at how solar panels are constructed to better understand  the effects of shading.


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## NoGoodAtScreenNames (Aug 11, 2020)

On a kwh basis this will nearly cover my yearly use. However, my net metering kind of sucks. It encourages load shifting our use to the daytime when the panels are running.

I pay $0.16 per kWh for anything I pull from the grid and get paid back the wholesale rate of $0.04 for anything I send back to the grid. It’s not rolled at all. Basically excess daytime production reduces my nighttime rate by 25%. There is talk of updating the metering rules to have some rolling period - even day to day would be good. But I’m not banking on it.


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## semipro (Aug 11, 2020)

NoGoodAtScreenNames said:


> On a kwh basis this will nearly cover my yearly use. However, my net metering kind of sucks. It encourages load shifting our use to the daytime when the panels are running.
> 
> I pay $0.16 per kWh for anything I pull from the grid and get paid back the wholesale rate of $0.04 for anything I send back to the grid. It’s not rolled at all. Basically excess daytime production reduces my nighttime rate by 25%. There is talk of updating the metering rules to have some rolling period - even day to day would be good. But I’m not banking on it.


Something like this was an option for us in Virginia too - buy at the retail rate and sell at the wholesale rate.
It was either this or reconcile yearly.  We'll see how it all works out after a few years.


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## semipro (Aug 11, 2020)

NoGoodAtScreenNames said:


> I pay $0.16 per kWh for anything I pull from the grid and get paid back the wholesale rate of $0.04 for anything I send back to the grid. It’s not rolled at all. Basically excess daytime production reduces my nighttime rate by 25%. There is talk of updating the metering rules to have some rolling period - even day to day would be good. But I’m not banking on it.


That stinks.  I read through Mass. net metering and it looks like you reconcile monthly - not very helpful.


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## NoGoodAtScreenNames (Aug 11, 2020)

semipro said:


> That stinks.  I read through Mass. net metering and it looks like you reconcile monthly - not very helpful.



I’m in a municipal department. I hear we are cheaper than for profit companies but they are exempt from a lot of regulations around solar.


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## begreen (Aug 11, 2020)

We're coming to the end of our first contract with PSE. It paid the going rate for net metering and $0.54/kW annual credit at first. The credit dropped to about $0.48/kW, but still is ok. It was a sweet deal if you got in early. The caveat though was that the system and panels had to be WA state made. Our second array is under a fairly decent contract, but not as good. But the panels cost less by then and we already had the inverter to tie in to.


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## John Ackerly (Nov 6, 2020)

I may have missed this, but if you use much A/C in the summer, those trees can really help.  We are letting the trees grow tall on the north side of the house and on the south side, I climb up and trim them every year so they provide some shade but not on the panels.


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## stoveliker (Nov 6, 2020)

I have some oaks in the West (ridgeline being North-South, equal # of panels on both sides) that shade late sun in Summer, and less late sun in Winter.
However, our system was designed to cover my yearly needs with the trees there - being lucky to have a meter that runs backwards in Summer (rather than getting paid pennies per kWh). 

Given your metering, the question is whether your system was designed to have you financially break even, OR to produce as much as you use, with the latter still not being break even in your metering.

The former situation means nothing needs to be done. In case of the latter, cutting trees will help, but not much given the metering. Instead, it might be worth looking into a battery system, to avoid having to pay for power used at night. Winter will still suck, but it's tough to change the rotation axis of our planet...

The bottom line is that cutting trees has much less effect than the financial situation of the metering. I'd leave them standing, unless you have other reasons than solar to cut them down.

That's just an opinion, and as we see above, you can find those all over the place...

Good luck deciding!


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## NoGoodAtScreenNames (Nov 7, 2020)

We ended up taking them down after all. In the end it was a combination of solar, tree safety and letting more light into the yard and house. The trees don’t do much to help with the AC demand in the summer. Their shadow was gone from the house by mid morning.

In my original post I was worried about winter but not thinking as much about fall. The sun sinking lower with the leaves still on the trees was really delaying the upward trend towards my peak. I face SE so the morning to midday is most important to me. I took a look at the last perfectly clear days before and after the removal. You can see a more gradual uptick as the sun rises instead of the steep climb as the shadows cleared. So it definitely will be increasing my solar access for at least 6 months of the year. Whether that works to pay off the tree work, I’m doubtful. Whenever I have tree work done I always feel a little guilty before doing it and then being very happy after they are gone. That was the case here.

Got a good amount of wood out of. 5 large oaks in all, 3 of which helped with the solar. Looks like I’ll get about 4 or 5 cords out of it that I won’t be buying, so that helps too.


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