Shade Analysis / Report

[ElectricianJim]

I figured I would use the pandemic slow down to install rooftop solar PV on my own home. For personal benefit and to pickup some solar skills and experience for my electrical contracting business.

Reviewing my local utility application process they require I provide a "Shade Report" and that I use that information in calculations regarding expected power production that are required.

Is that something I should sub out to someone? How do I get that done? How have others done this for your projects?

Further complicating matters is that I am planning on having trees removed as part of the project. It sounds like that needs to be done first? (before I even apply)

Thanks in advance.

[bob-n]

The power company wants to know what to expect from your system so that they can budget the grid. They don't need 3rd decimal place accuracy. They want to know whether you'll be producing 13 MWh per year or 6 MWh per year.

If you're at all analytical, you can write your own shade report. Have you been through a model like PVWatts? That would tell you what your panels would put out without trees. You can then use a cell phone and a free app like "Scan The Sun" to assess how much shade you'll get. Either that, or you could make some rough guesses.

Tree removal can come at any time. You can send in your shade report assuming that the trees are down. Just make a note in the report that this analysis is based on the assumption that planned tree work is completed.

Trees hurt solar production, especially when the sun is low. But tree removal can be expensive, especially with big ones. For me, this is the toughest decision, and I still haven't made the call.

In my case, big pines shade my panels, but only in winter, late fall and early spring. I have microinverters, so a little shading doesn't drop out all of my power. I ran some numbers and estimated that each tree is costing me $20 per year in energy (might be $15 or $25, but close enough). Taking down one tree is roughly $300. That makes tree removal hard to justify.

On the other hand, trees get larger with time, so are cheaper to remove now than later and will rob more power as time goes on.

[J.P.M.]

I'd start by contacting the POCO and asking them for particulars about what type of information they require, the format they want, and any suggestions or information they may have with respect to how best to conform to their requirements. You want to conform, cooperate and supply the info the POCO wants in a format that's acceptable to them, but you have questions and need more information from them to do so.

Depending on what you find out about what might be acceptable to the POCO, and depending on your location, some solar peddlers can do a shade analysis. Prices vary. Some less populated locations may not have such services. In using vendors for such services, I'd be careful about the quality of the work and the tools (if any) used. One place where POCO info might be helpful is to locate such services.

There are also shading tools available for purchase/rent. Not a plug, but one such tool is the "Solar Pathfinder". There are other tools but that's one widely used tool that will probably give what your POCO wants in a format they'll recognize. Again, call the POCO and make sure.

That product is also what may be used if you farm out the anaylsis. The buy in is a bit steep for a one time use (~ $500 or so w/software).

I'd respectfully suggest you might consider a DIY analysis and renting a shade analysis tool. I've used the pathfinder tool a few times. Quick learning curve, but read up before/if you rent. There are others as well.

Perhaps the cost of renting vs. farming out the analysis might be close. If so, and depending on what the POCO has to say when you call them on what they'll accept, the decision may then come down to how much you can trust a vendor to do it correctly and professionally, and in a way the POCO won't kick back vs. your confidence to do a decent shade analysis.

To reiterate: Call the POCO and ensure you understand what they want before you decide what to do w/respect to their shade analysis and also that you're speaking with someone who is familiar with the requirements you're asking about. They may waive it, or it may be a tactic to discourage residential PV, or something else/all of the above. I'd call them, take a shot ,and see if I could convince then a waiver is in their best interest - but, whatever you get from them, get it in writing.

In any case, since an array in shade, depending on the degree of shade, is to some extent analogous to having a race car with a governor on the engine , I'd think doing any shade modifications/tree trimming/removal before any shading analysis would be a good idea unless the NEM policies of your POCO would become less favorable as a result of an array being more shade free. If you haven't done so already, see/study your POCO's NEM agreement/policies before you call them and do so with an one eye toward reading between the lines, including anything that talks about future generation changes (as in increases as a result of shade changes or array size increases, etc.).

Welcome to the neighborhood.