Tilt?

[vnatale]

My zip code is 01351. My ground mount will be facing south.

What is the optimal tilt for my panels?

I've been given these in various quotes.

10

28

15 or 18

[solar pete]

Hi There, the optimal tilt angle changes with the seasons. If the ground mount is not easily adjustable I would go 15 to 18 or maybe 22, I wouldn't do 10 or 28, but hey my experience is in Australia, hope that helps, cheers

[Mike 134]

You could use https://pvwatts.nrel.gov/ and plug in various tilt angles and see the results for yourself.

[littleharbor2]

"Solar Tilt" is a great app. Built in angle gauge even.

[J.P.M.]

There are many ways to interpret what the "optimal "tilt angle might be.
And, BTW, the azimuth angle is also important with that optimal azimuth rarely being true south at 180 degrees.

Some of those ways to view optimal orientation (both tilt and azimuth) are:
- The orientation that optimizes the annual system production in kWh/yr. per installed STC W regardless of cost/installed STC W.
- The orientation that produces the most revenue to offset an electric bill per installed STC W.
- The orientation that has the lowest installed cost per STC W regardless of how much revenue the system produces.
- The orientation that is easiest to clean and service (this one is usually not considered at all - a fact that many system owners come to regret).
- The orientation that produces the lowest long-term life cycle cost per installed STC W.

There are other orientations that may be viewed as optimal depending on who sets the priorities and/or just what the application is.
Usually, a well thought out system design will wind up with a size, orientation and other design parameters that are a compromise of the particular application taking as many considerations into account as deemed relevant to the application.

Set your system priorities, then design around those with safety and your priorities in mind (in that order).

Dirty little secret: Many users want to eliminate their electric bill and wind up with a system that produces a long term per kWh cost that is greater and more hassle to achieve than simply going with no PV at all and investing the money spent in something for the long term.

Take what you want of the above. Scrap the rest.

[vnatale]

There are many ways to interpret what the "optimal "tilt angle might be.
And, BTW, the azimuth angle is also important with that optimal azimuth rarely being true south at 180 degrees.

Some of those ways to view optimal orientation (both tilt and azimuth) are:
- The orientation that optimizes the annual system production in kWh/yr. per installed STC W regardless of cost/installed STC W.
- The orientation that produces the most revenue to offset an electric bill per installed STC W.
- The orientation that has the lowest installed cost per STC W regardless of how much revenue the system produces.
- The orientation that is easiest to clean and service (this one is usually not considered at all - a fact that many system owners come to regret).
- The orientation that produces the lowest long-term life cycle cost per installed STC W.

There are other orientations that may be viewed as optimal depending on who sets the priorities and/or just what the application is.
Usually, a well thought out system design will wind up with a size, orientation and other design parameters that are a compromise of the particular application taking as many considerations into account as deemed relevant to the application.

Set your system priorities, then design around those with safety and your priorities in mind (in that order).

Dirty little secret: Many users want to eliminate their electric bill and wind up with a system that produces a long term per kWh cost that is greater and more hassle to achieve than simply going with no PV at all and investing the money spent in something for the long term.

Take what you want of the above. Scrap the rest.

To reinforce ... this is a ground mount.

This time around I'm not looking for solar to be a good investment. It's to protect me from me. I make a one-time investment and I then use as much electricity as I like. Unlike now where I use the minimum electricity because I obsessively scrimp on electricity use so as to generate the lowest possible bill. Some days recently I've only been using 5 kWh per day.

However, if I were to use as much as I wanted that could be 22 kWh per day (after replacing current vehicle with an EV going 4,000 miles a year).

Taking your points above one-by-one:

a. "The orientation that optimizes the annual system production in kWh/yr. per installed STC W regardless of cost/installed STC W."

With a ground mount is there going to be any difference in cost for different tilts / azimuth?

b. "The orientation that produces the most revenue to offset an electric bill per installed STC W."

How is this any different from a.? The more I produce the more revenue I produce.

c. "The orientation that has the lowest installed cost per STC W regardless of how much revenue the system produces."

Again, with a ground mount of a certain amount of panels is there a different cost depending upon tilt and azimuth?

d. "- The orientation that is easiest to clean and service (this one is usually not considered at all - a fact that many system owners come to regret)."

One of the major advantages of a ground mount over a roof mount?

e. "The orientation that produces the lowest long-term life cycle cost per installed STC W."

Again, not seeing how there would be different costs based upon tilt and azimuth?

Finally, the speed with which all the solar companies create all their quotes I'm not getting the impression that any of them may be doing this: "Usually, a well thought out system design will wind up with a size, orientation and other design parameters that are a compromise of the particular application taking as many considerations into account as deemed relevant to the application."

They all seem to want to make a quick sale and I can see how they easily get that from way too many consumers.

Case in point was my friend telling me that somehow some solar vendor had contacted his wife and that she was ready to sign up for it based upon that one proposal from that one vendor.

So far I've got 12 quotes from 7 vendors and waiting for one from an 8th.

Just recently I engaged with EnergySage but they make the automatic assumption you only want to do a ground mount. Plus, all the vendors quote on your current usage without determining if it will be going up. Basically not a good use of time to deal with them.

I have a preference to making my choice from among the many local companies who have been doing this work for years. I have a bias against the large companies.

[J.P.M.]

To reinforce ... this is a ground mount.

This time around I'm not looking for solar to be a good investment. It's to protect me from me. I make a one-time investment and I then use as much electricity as I like. Unlike now where I use the minimum electricity because I obsessively scrimp on electricity use so as to generate the lowest possible bill. Some days recently I've only been using 5 kWh per day.

However, if I were to use as much as I wanted that could be 22 kWh per day (after replacing current vehicle with an EV going 4,000 miles a year).

Taking your points above one-by-one:

a. "The orientation that optimizes the annual system production in kWh/yr. per installed STC W regardless of cost/installed STC W."

With a ground mount is there going to be any difference in cost for different tilts / azimuth?

b. "The orientation that produces the most revenue to offset an electric bill per installed STC W."

How is this any different from a.? The more I produce the more revenue I produce.

c. "The orientation that has the lowest installed cost per STC W regardless of how much revenue the system produces."

Again, with a ground mount of a certain amount of panels is there a different cost depending upon tilt and azimuth?

d. "- The orientation that is easiest to clean and service (this one is usually not considered at all - a fact that many system owners come to regret)."

One of the major advantages of a ground mount over a roof mount?

e. "The orientation that produces the lowest long-term life cycle cost per installed STC W."

Again, not seeing how there would be different costs based upon tilt and azimuth?

Finally, the speed with which all the solar companies create all their quotes I'm not getting the impression that any of them may be doing this: "Usually, a well thought out system design will wind up with a size, orientation and other design parameters that are a compromise of the particular application taking as many considerations into account as deemed relevant to the application."

They all seem to want to make a quick sale and I can see how they easily get that from way too many consumers.

Case in point was my friend telling me that somehow some solar vendor had contacted his wife and that she was ready to sign up for it based upon that one proposal from that one vendor.

So far I've got 12 quotes from 7 vendors and waiting for one from an 8th.

Just recently I engaged with EnergySage but they make the automatic assumption you only want to do a ground mount. Plus, all the vendors quote on your current usage without determining if it will be going up. Basically not a good use of time to deal with them.

I have a preference to making my choice from among the many local companies who have been doing this work for years. I have a bias against the large companies.

Those were just a few ways to define what "optimal orientation" might be.
Your definition of "optimal orientation" needs to be defined.

A.) Yes. different array orientations will produce different annual production per installed STC W.
An array oriented to produce the maximum annual production per installed STC W will result in a smaller and therefore less expensive array and system. For a specific annual electrical design load, particularly with a net metering plan that does not have variable rates and/or energy storage, designing/array sizing this way may result in a more cost-effective system.

B.) This method is often used when the system will operate under a Time Of Use (T.O.U.) tariff (billing schedule).
Often, POCO's (POwer COmpanies) will charge (or pay) more per kWh as f(time of day). This means that the highest (cost/delivered kWh)*(kWh produced/kWh) product summed over 8,760 hrs summed over a year will have an array orientation that will most likely be different than that found in "A" above.

C.) This is the low initial cost option that most ignorant solar customers choose. They're the "my electric bills are killing me and I must do something" crowd. So they take what looks like the easy way out and get a bunch of quotes and get confused by terms they're clueless about , take the lowest dollar bid, get B.S'd by peddlers who ought to be selling driveway sealer door to door and wind up getting screwed. This is also the all too common design approach to "optimal orientation".

D.) This is not a bad set of design considerations but not the only ones of a good design.

E.) This is the common method used by serious designers of capital equipment taking account of (among other parameters) the time value of money.
For solar energy equipment, the goal of the analysis can be viewed as the determination of the least cost method of meeting the energy need considering both solar and non solar alternatives.
For solar only alternatives such as what you seem to have in mind, the problem boils down to finding the system size (and so the orientation) that gives the lowest system cost to meet the design load.

NOMB, but it looks to me like you're relying too much on peddlers and others to tell you (and sell you) not only what you need but also what you want. You're too trusting or at least willing to swallow what they're feeding you. Your lack of knowledge is your worst enemy in this situation.
Read "Solar Power Your Home for Dummies" and continue to use PVWatts as a preliminary design tool after you read all the help screens. All that with the goals of knowing what you want, setting design goals and knowing the answers to all the questions you have already asked and will ask vendors and others in the future before you ask them. Then do some serious homework on local companies before you make a choice.

Take what you want of the above. Scrap the rest.

[vnatale]

Those were just a few ways to define what "optimal orientation" might be.
Your definition of "optimal orientation" needs to be defined.

A.) Yes. different array orientations will produce different annual production per installed STC W.
An array oriented to produce the maximum annual production per installed STC W will result in a smaller and therefore less expensive array and system. For a specific annual electrical design load, particularly with a net metering plan that does not have variable rates and/or energy storage, designing/array sizing this way may result in a more cost-effective system.

B.) This method is often used when the system will operate under a Time Of Use (T.O.U.) tariff (billing schedule).
Often, POCO's (POwer COmpanies) will charge (or pay) more per kWh as f(time of day). This means that the highest (cost/delivered kWh)*(kWh produced/kWh) product summed over 8,760 hrs summed over a year will have an array orientation that will most likely be different than that found in "A" above.

C.) This is the low initial cost option that most ignorant solar customers choose. They're the "my electric bills are killing me and I must do something" crowd. So they take what looks like the easy way out and get a bunch of quotes and get confused by terms they're clueless about , take the lowest dollar bid, get B.S'd by peddlers who ought to be selling driveway sealer door to door and wind up getting screwed. This is also the all too common design approach to "optimal orientation".

D.) This is not a bad set of design considerations but not the only ones of a good design.

E.) This is the common method used by serious designers of capital equipment taking account of (among other parameters) the time value of money.
For solar energy equipment, the goal of the analysis can be viewed as the determination of the least cost method of meeting the energy need considering both solar and non solar alternatives.
For solar only alternatives such as what you seem to have in mind, the problem boils down to finding the system size (and so the orientation) that gives the lowest system cost to meet the design load.

NOMB, but it looks to me like you're relying too much on peddlers and others to tell you (and sell you) not only what you need but also what you want. You're too trusting or at least willing to swallow what they're feeding you. Your lack of knowledge is your worst enemy in this situation.
Read "Solar Power Your Home for Dummies" and continue to use PVWatts as a preliminary design tool after you read all the help screens. All that with the goals of knowing what you want, setting design goals and knowing the answers to all the questions you have already asked and will ask vendors and others in the future before you ask them. Then do some serious homework on local companies before you make a choice.

Take what you want of the above. Scrap the rest.

A) You have described my situation. I get net metering at 92% no matter when I produce it. My rates are the same every hour of the week and we have no tier pricing. Rates the same for every kWh used no matter when used or how much used in a month.

B) Not my situation.

I was advised by you or someone else here a few years ago to read Solar Power Your Home for Dummies, which I did.

I am not relying upon the vendors to tell me what I need. I am distressed that it is the opposite. Though I have detailed records of my historical electrical use on every circuit and projections for each of them ... none of them want to get involved in revising those estimates. They just accept whatever total projected annual kWh I come up with. The latest was 83% more than I am currently using.

I'm not going to become a solar design expert on the basis of one installation. I need to rely upon the expertise of these companies who have done many installations over many years.

Also, when I came here a few years ago it seemed to be a quite active forum. I was expecting the same when I came back but it's felt more like a ghost town with the norm getting no responses on posts I create.

I am in a financial forum where we do discuss solar topics.

This is where I currently am at in terms of my comparing the various quotes I have p.pdf received.

[vnatale]

Those were just a few ways to define what "optimal orientation" might be.
Your definition of "optimal orientation" needs to be defined.

A.) Yes. different array orientations will produce different annual production per installed STC W.
An array oriented to produce the maximum annual production per installed STC W will result in a smaller and therefore less expensive array and system. For a specific annual electrical design load, particularly with a net metering plan that does not have variable rates and/or energy storage, designing/array sizing this way may result in a more cost-effective system.

B.) This method is often used when the system will operate under a Time Of Use (T.O.U.) tariff (billing schedule).
Often, POCO's (POwer COmpanies) will charge (or pay) more per kWh as f(time of day). This means that the highest (cost/delivered kWh)*(kWh produced/kWh) product summed over 8,760 hrs summed over a year will have an array orientation that will most likely be different than that found in "A" above.

C.) This is the low initial cost option that most ignorant solar customers choose. They're the "my electric bills are killing me and I must do something" crowd. So they take what looks like the easy way out and get a bunch of quotes and get confused by terms they're clueless about , take the lowest dollar bid, get B.S'd by peddlers who ought to be selling driveway sealer door to door and wind up getting screwed. This is also the all too common design approach to "optimal orientation".

D.) This is not a bad set of design considerations but not the only ones of a good design.

E.) This is the common method used by serious designers of capital equipment taking account of (among other parameters) the time value of money.
For solar energy equipment, the goal of the analysis can be viewed as the determination of the least cost method of meeting the energy need considering both solar and non solar alternatives.
For solar only alternatives such as what you seem to have in mind, the problem boils down to finding the system size (and so the orientation) that gives the lowest system cost to meet the design load.

NOMB, but it looks to me like you're relying too much on peddlers and others to tell you (and sell you) not only what you need but also what you want. You're too trusting or at least willing to swallow what they're feeding you. Your lack of knowledge is your worst enemy in this situation.
Read "Solar Power Your Home for Dummies" and continue to use PVWatts as a preliminary design tool after you read all the help screens. All that with the goals of knowing what you want, setting design goals and knowing the answers to all the questions you have already asked and will ask vendors and others in the future before you ask them. Then do some serious homework on local companies before you make a choice.

Take what you want of the above. Scrap the rest.

This is where I gave a lot of detail here regarding my present situation:

Assistance in determining size of Solar installation - Solar Panels - Solar Panels Forum (solarpaneltalk.com)

[Mike 134]

I'm not going to become a solar design expert on the basis of one installation. I need to rely upon the expertise of these companies who have done many installations over many years.

Just an FYI none of the companies double back 2-3-5 years later and see how their design worked out. On the sales side their only "expertise" is separating you from your $$. On the install side, they need to know enough to not have call backs from the install, as to whether it serves the customer 's needs that's on the sales guy.

[J.P.M.]

A) You have described my situation. I get net metering at 92% no matter when I produce it. My rates are the same every hour of the week and we have no tier pricing. Rates the same for every kWh used no matter when used or how much used in a month.

B) Not my situation.

I was advised by you or someone else here a few years ago to read Solar Power Your Home for Dummies, which I did.

I am not relying upon the vendors to tell me what I need. I am distressed that it is the opposite. Though I have detailed records of my historical electrical use on every circuit and projections for each of them ... none of them want to get involved in revising those estimates. They just accept whatever total projected annual kWh I come up with. The latest was 83% more than I am currently using.

I'm not going to become a solar design expert on the basis of one installation. I need to rely upon the expertise of these companies who have done many installations over many years.

Also, when I came here a few years ago it seemed to be a quite active forum. I was expecting the same when I came back but it's felt more like a ghost town with the norm getting no responses on posts I create.

I am in a financial forum where we do discuss solar topics.

This is where I currently am at in terms of my comparing the various quotes I have [ATTACH]n443114[/ATTACH] received.

As you probably know, PVWatts does not account for shading.
The best way to handle array shading is with a chain saw.
AND/OR, because you are designing for a ground mount, simply put the array where the shade ain't.
There is software that will do loose approximations for shade, but IMO only and for many reasons which sounds (reads) like you don't want to waste you time with, most of them are not worth a bucket of warm snot in terms of reliability. They're also pretty inconsistent from one another in terms of results. And, like a lot of solar design tools, they're all nearly impossible to verify. A back of the envelope method I've found that is about reliable as the other tools is to get the area of the worst shading situation you're likely to encounter on the array, use half of that area and ratio that area to the full array area and then either decrease the array's annual output by that ratio for the reduced annual output due to shading or increase the array size by the same percentage to make up the difference.

In the meantime, using PVWatts and your zip, a 35 degree tilt and a 180 degree azimuth and no shading will maximize your annual output at approx. 1,348 kWh/yr. per installed STC kW.
Divide your annual load by that number for a preliminary array size in kW.
A few degrees variation of either tilt or azimuth will result in only a few kWh/yr. or less of a penalty.
BTW, that's using a 10% system loss number and not the 14% that the model defaults to.

A 42 degree tilt while keeping the same 180 degree azimuth will have the advantage of possibly making the array easier to clean (and will also help to keep clean) and also help keep it snow free which will also impact the annual production but will still produce ~ 1,336 kWh/yr. per installed STC kW before any shading or snow penalty.

Other items in your post:
- I was probably the source of the advice on the Dummies book.
- If you rely on the expertise of those companies, you risk relying on vapor. Get your own knowledge of take your chances.
- This forum is not what it once was. When I joined in Aug., 2013, it was a powerhouse of information and not much B.S. got through the mods and the knowledgeable members. Now, residential PV has probably run its course so there are fewer posters and PV is pretty much a commodity so there's a lot less interest. Also, political correctness has gutted the hope of honest and frank communication. Also, a lot of unqualified vendors have fallen by the wayside along with a good number of reputable and reliable vendors, all that making for a lot less conversation.

If you're interested in solar process economics, A good, accurate and concise (21 page) discussion of solar process economics can be found in Duffie and Beckman's "Solar Engineering of Thermal Processes". It's primarily an engineering text focusing on solar thermal but the solar process economics as described in the book or elsewhere for that matter are also applicable to PV and the chapter in the book has a good bibliography for further info on solar process economics.
There is also what is probably the best (and also concise) chapter on Solar photovoltaic engineering and design that's about the best I've seen. The book is a bit dated but also a free PDF download.