Ground mount vs Roof mount?

1.) Have you figured out what your current annual kWh load is ?
2.) Have you estimated what your furure annual load(s) might be ?
3.) Have you determined how much of your current and future electrical load you want to offset with a PV system ?
4.) Have you done your own preliminary sizing yet using PVWatts ?
5.) If so, have you run the models for the roof orientations and for an optimally oriented ground mount ?
6.) Do you have net metering from your power provider ?
7.) Have you checked local building codes etc. yet ?
8.) How many vendors have you contacted so far ?
9.) How much do you know about solar energy and PV ?

Ground mounts are more expensive than roof mounts. How much ? hard to say. It depends on your application, how much you know about PV and how good your negotiating skills are - among other things. But the same can be said about roof mounts.

However, ground mounts offer advantages in siting, accessibility for servicing and cleaning that roof mounts don't have. But, they also may require more hoop jumping when it comes to your building dept. Be prepared to maybe put a fence around it among other requirements. On the other hand, a ground mount may not need rapid shutdown capabilities. Also, if shade free (and given the better placement/orientation options a ground mount offers, it ought to be), a ground mount can make better use of string inverters which make for an inherently more reliable system (fewer parts to fail) and, because string inverter systems are usually less expensive than micros or optimizer systems, they can slightly mitigate the added cost of a ground mount that uses optimizers or micros.

Depending on shading and orientation of your roof areas, and the suitability of a proposed area for a ground mount, the advantages of a ground mount may make up for some of the extra cost.

Also, if you haven't done so already, I'd check with your local building dept. for what they require for PV in general. Do not treat them as an afterthought. If building permits are required, they can be your best friend if you involve them or your worst enemy if you ignore them.

As for roofs, That's a tough call. If you feel a new roof under a rooftop array is in your best interest, that would seem to me to make a ground mount a better choice.
How long to you expect to keep the house ?

You state all the vendors you've contacted are proposing a roof mount. That may be because most arrays are roof mounted so vendors assume that's what you want.
Do the vendors you contacted know you might be interested in a ground mount ?

Bottom line: If it was me, I'd first get more educated and then do a ground mount, but I'd get more quotes from better vendors.

At this time and place, your likely lack of knowledge about PV is your worst enemy. If you haven't done so already, get and read a copy of "Solar Power Your Home for Dummies". Not a perfect tome, but a cheap investment that pays big dividends. Customer ignorance is the red meat vendors thrive on.

Then, set your project goals, get your current and future loads, do your preliminary sizing with PVWatts, figure out whether you want a ground or roof mount (or PV at all for that matter) before you get more quotes from local vendors who are also established electrical contractors who will be around in the future, and will do a ground mount if that's what you decide is the best fit for your project goals.

I have a list of 52 reasons to prefer a ground mount, but lower cost
is not one of them. The ground mount will get the most performance
by allowing optimum orientation and snow removal. Here I get a lot
more out of my inverters by using strings in parallel facing east and
west, but this needs to have an angle generally steeper than roofs.

Bruce Roe

IMO, to a DIYer a ground mount is a lot easier to DIY. If you do not value your time, then DIYing a ground mount can offset paying someone to do a roof mount. Most people are very uncomfortable about working on roofs, some arent (like myself). If you are paying for either option, no way will a ground mount cost less. Panels are relatively cheap and if you have room on the roof a couple of extra panels can make up for less-than-optimal orientation now that roof mounted systems have to have panel level optimization. If you are in snow zone, a ground mount properly designed is lot easier to keep the panels clean. I am a fan of adjustable tilt angle which boost year-round output but is more complex. I am also an engineer and a DIYer so I may have skills you do not have. I have installed three arrays at my home over the years, One small wall mount, one pole mounted ground mount and one roof mount. In all cases I did the install completely solo with the exception of digging a hole and trench. I am in no rush when I do it and think out the work in advance and this included lifting the panels up on a second floor roof solo. I am planning a future array for new home and expect it will be ground mount DIY.

Generally, in snow areas having to put a fence around a ground mount is not an issue as the wiring behind the panels in "inaccessible" due to elevation. Unless the AHJ is going above and beyond code, and requiring a fence specifically, its not that difficult to install hardware cloth behind the panels in areas where wiring is exposed.

There is a downside to a ground mount and that is foreign objects tend to be thrown inadvertently at panels located near the ground, potentially damaging them. Could be from kids playing, lawnmowers or snowblowers. The upside is design an array right and they can be a nice shady area. There are some slick designs out there of arrays integrated into pergola type structures and garages. In most cases these are also DIYs.

Although the cost of the frame installed on the ground is high, it is relatively convenient for later maintenance. You don’t need to climb to the roof to take care of the dust and leaves on the solar panel. The most important thing is to prevent fire caused by the aging of the line for too long. The place is also as mentioned above, will be damaged by unexpected things.

I note most ground mounts are quite elementary, not providing
a number of possible advantages. Things like ease of snow
removal, variable tilt, and more. In 9 years I have never had a
panel damaged by a flying object (or anything else), they are
tough. Bruce Roe

Bruce, is your list posted here by any chance? If not it should be, maybe in the stickies section.

52 reasons, not all will apply to any particular ap. Bruce Roe

52 Reasons for GROUND MOUNTING Solar Panels
1. Significant Other won't complain about looks. 1 July 22
2. No roof leaks
3. No reroofing problems
4. No 3' setback rule
5. No rapid shutdown requirements
6. Flexibility in location, to avoid shadows and save trees.
7. Easier panel repairs
8. Elevation angle change or tracking an option
9. Choice of initial angle
10. Less risk of harm in construction by not lifting components to the roof
11. Serviceable safely in all seasons
12. Fire hazard from panels distanced
13. No roof orientation direction issue
14. Layout not complicated by things like vents, chimneys, etc.
15. Easier to landscape mount
16. NOT feeling like I have a giant tick on the roof
17. No hiring a structural engineer to analyze roof loading
18. No walking on panels to inspect
19. Far easier to wash off dirt
20. Far safer to wash off dirt
21. Far easier to check for hot (potentially failing) MC4s
22. Ease of spot checking performance & tracking down any issue
23. Much easier to work on at night.
24. Less likely to be disturbed by high wind.
25. No problems trying to perfectly align with an imperfect roof.
26. Generally cooler operation than roof mount.
27. Avoid need for a building permit in some areas.
28. Can avoid glare problems by placing far out of sight.
29. Will not encourage squirrels and birds to build nests on your roof.
30. Trying to set up a solar pathfinder on a roof kind of s**ks.
31. No contract arguments about roof penetration points
32. No problem with snow blocks sliding off panels and damaging lower
panels, roofs, other equipment, or personal, no snow brakes.
33. No losing most winter production because snow slides are blocked.
34. No uneven heating up of panels due to restricted ventilation.
35. There is no limitation using older, less efficient panels to build up a system.
36. No concern with aesthetics with mixed equipment
37. Simpler to get back in service after a damaging violent storm.
38. Ease of using thru bolts to retain panels, instead of slip prone clamps.
39. Snow removal is at least viable.
40. Array can be designed to greatly aid in snow removal.
41. No roofers not willing to take panels off roof, due to liability
42. Much easier to directly ground against lightning
43. Removal of shade on a remote array will not impact the house.
44. Much less size limitation
45. Nobody wants to "experiment" on their own house.
46. No wind noise or possible vibration and deterioration issues.
47. No daily expansion/contraction noises.
48. No roof concerns if array is to be moved to another address.
49. Clumsy installers cannot break your roof tile.
50. No increase in house insurance cost.
51. No wires on roof
52. No panel ice clumps sliding off and damaging gutters.

Bruce is our ground mount guru when it comes to solar panels. He has more knowledge then most and has a very large array on his property.

Another reason that I did not see on Bruce's list is the expense of Rapid Shutdown Devices which are required on most roof installs.

That is #5

Sorry to take so long to respond to your excellent reply. Because of other house / life needs I had to put on the shelf until now the investigation of a solar installation.

To answer your questions.

1) I am an accountant and am even far more detail oriented than the typical accountant. Since 1998 I have an Excel worksheet that details every single line item for every one of my electric bills. One of the tables I have in that worksheet shows the average kWh per day I have averaged for each month (since 1998) and the annual consumed for each year.

2) I used the information in #1 to do an initial sizing of a system. The wild card was how much it was going to cost me for dehumidification from May to September. I made a guess. However, I put the dehumidifier on an electricity meter and was shocked to see how much electricity it was consuming. As much as all else in the rest of my house! After I finally realized that I substituted a brand new dehumidifier for that old, energy inefficient one. My electricity meter told me it was using 25% to 30% electricity as the old one had been using. Shortly after I had my heat pump electric hot water heater repaired. I bought it ten years ago and somewhere over 2 years ago the fan stopped working so it stopped working as a heat pump and was strictly working on electric resistance - the most expensive mode. Once I had the fan replaced the unit also was using only 25% to 30% as much electricity as it was using pre-repair mode.

Two things which decreased the amount of electricity I thought I'd be needing.

Somehow sometime in the fall I was led to investigating mini-splits / heat pumps. That led to two weeks ago the installation of three mini-splits (18,000 BTU and 2 6,000 BTU) with each having its own heat pump.

Converting from oil heat to electric heat is obviously going to increase my future electricity load. How much I did not know.

However, two years ago I had this device installed in my electrical panel.

Smart Home Energy Monitor with 16 50A Circuit Level Sensors | Vue - Real Time Electricity Monitor/Meter | Solar/Net Metering - - Amazon.com

It tells me in real time how much electricity in kWh each of my circuits is using plus I can get csv reports to open in Excel of historical use by circuit by seconds, minutes, 15 minutes, hours, days, weeks, months, years.

Unfortunately, when we initially installed it it took more time to get it connected to the internet than it did to install it in the electrical panel. For the past two years it has worked off and on. However, last week I installed an auxiliary router in my basement three feet from it in the electrical panel and took care of a few other issues so that the device is now super reliable. Which is what I needed to determine how much electricity these mini-splits / heat pumps are consuming. I will need to monitor this for at least a month. Preferably longer.

3) I want 100% of my current and future electrical needs to be offset by solar. I do not have a dishwasher or dryer and never plan to. My stove is unplugged. Doing any "cooking" via microwave. I drive only 4,000 miles a year so an electric car would not be justified on a financial basis. With these mini-splits and heat pumps now having been installed I cannot foresee anything else that would increase my annual electric load. By the way, I plan to use the mini-splits / heat pumps only for heating. None for air conditioning. I'm not an air conditioning fan, probably only had it on for an hour in my car all last summer.

4) I have not done my own sizing using PVWatts but the vendors who have given me quotes have. Maybe, though, I will try to use it for my proposed ground mount solution.

5) They have run them for the roof orientations but not for a ground mount. I'd looked at solar prior in 2016 and a ground mount was quickly ruled out due to zoning laws. I did not have enough property to provide proper distance from other neighbors' properties. Those zoning bylaws seem to have been revised twice since then so that it will not now be an issue because of distance. But I most likely would need to get a zoning variance for the square footage of a ground mount. I did not know any of this when getting quotes last summer and did not even consider the ground mount possibility until around the time I initially asked the question here late August.

6) Yes. Have net metering.

7) There were three big impediments last summer to me quickly accepting any solar bid. The first one was the solar tax credits. Until they got extended past 2022 it was not going to work for me tax-wise. Once they got extended past 2022 that issue was off the table. I have a 100 amp electrical service. One vendor stated that might not be enough and that I might have to upgrade it, which could cost $4,000 to do. That would have ended it. But all the vendors ending up telling me that the 100 amp service was fine. Then another issue was if the electric company would have to do any transformer modifications to accommodate my installation. Those costs would all be passed on to me. Another thing that might have ended it for me. But just about all the vendors told me that with the relative small system I'd be getting that there would probably be no transformer work required. Another was if there had to be modifications to the roof inside the attic to support panels on the roof. I think this was going to be minor to none.

Tomorrow I will be calling my town's building inspector and zoning department to see exactly what applies to me regarding a ground mount. I know that they'd have no issues with a roof mount.

8) Last summer I contacted many vendors and received quotes from six of them. Today I've updated those six vendors with my new information of all that has happened electricity-wise since last summer plus I've contacted many more vendors today and yesterday. For my heat pump / mini-splits I contacted 40 vendors. Had 12 quotes and quickly narrowed them down to the top 4 and then my final choice. I am able to keep things organized and make analytical comparisons. I ask a lot of questions.

9) Compared to most people in this forum I know probably next to nothing but compared to the average person I know a lot.

My negotiating skills?

In a prior job I used to buy up to a million $ Euro contracts. I had about three sources I'd call each time and ask each of them to give me a rate. I would be buying 97% of them from one source. But if he was $5 more expensive than one of the other source ... he lost that contract. I had zero loyalty except for getting the best price every single time. He's say he could meet or beat that other source's rate but I eventually got across to him that when I called him for a quote I wanted his rock bottom, best rate from the start.

With these competing solar vendors I will get the message across to them that they are in competition with other companies that want my business.

However with our electric rates going up 20% this month (80% since July 1, 2020) ... I suspect that they all might now be having more business than they can handle. One who gave me a quote last summer today said she was booking into Fall 2023.

I do not believe that I'd need to put a fence around it. I did read about fences and ground mounts in the town zoning bylaws but I got the impression that they were referring to large industrial sized ones.

I expect to die in this house. I have owned it since April 30, 1982.

Last summer none of the vendors knew I wanted a ground mount because as explained above at the time I did not think it to be a possibility. Today I informed all six of them that this is what I believe might be best for me.

So far two have responded and will be giving me ground mount quotes. One, however, did bring up the whole what does the town permit, which led me to researching the town's zoning bylaws regarding it.

I think I have answered all your questions.

Now that almost everything else in my house has been accomplished getting a solar installation is now top priority for me. Especially in the light of this month's 20% increase in electricity (our variable cost per kWh is now about $0.362) and the greatly increased use of electricity due to the recently installed mini-splits / heat pumps.

Thanks again for all the great questions and all the additional information provided in your reply. I will also look into the book you cited. However, I think I may have already done so and was dissuaded from obtaining it due to its relative age. I'd hoped that it would have been revised so as to not be so old and possibly be outdated in certain areas.

I am an accountant / financial person and I am great at doing work at these keyboards and looking at a monitor. Doing any type of physical work in the real work is not my forte and just as people have paid me good money to work for them ... I will always pay people to do that type of work to make sure it gets done right.

I was going to ask you to provide these but was delighted to find these already here.

If I do have to go before my zoning board of appeals to get a zoning variance you can be assured that I will be using many of the items above to make my appeal! Thanks for providing it!

Is this book still recommended? Solar Power Your Home For Dummies Paperback – Illustrated, January 19, 2010


It came out 13 years ago which means it was written 14, 15 years ago. I'm hesitant to read anything about technology that is that old. Seems like it'd be so outdated on so many areas of the technology. I am quite surprised that the Dummy series has not updated it for so long.