To pull the trigger or wait, new solar PV

GW

I’m hoping to seek some opinion.

I’m looking to do some PV at my house. Last year the local PV man quoted me for a ground mount 5.3 KW system, about 250 feet away from my house. Cost seemed high, I decided to chill out.

This year he comes back and the price dropped about 8000. Not quite sure why.

Is the general consensus saying panels will continue to decrease in price? It looks like the 30% federal tax credit will be around for a while. There is a state incentive that seems somewhat tantalizing, and that program will eventually go away. He’s quoting a state incentive of about $11000. Even if he’s off a little it’s still a lot.

Thanks for your comments

Leonard

Don't know much about solar but seems nice to get the type that you can still make your own power if utility fails. That way don't need to run a fuel HUNGRY generator, at least during the daylight. In big ice storm in Maine ~ 8 years ago people were in dark for several weeks, so fuel costs can run VERY high even for a small gen if run 24/7.

Code says you can't backfeed into utility's street lines during a utility outage (so linemen don't accidentally get electrocuted). I suspect that creates an problem powering YOUR house during a utility outage, if you have the inverters distributed on back of each panel VS ONE stand alone inverter for the whole group of panels. There may be different types. Read with one master inverter it's easy power your OWN house during an outage.

Neice-in-laws house in Maine has about same 5 kw of solar, maybe 18 separate panels , looks like inverter on back of each panel.

Was told it didn't have one main inverter, that lead me to believe there was a small one on back of each panel. Then wires from those modual run to breaker box to "back feed" into service entrence to meter.

Run this way I don't think she could make her own solar electricity if utility had an outage, since each panel modual would shut down if no utility power present.

the_donut

Why not make it your roof? A coworker of mine did that a few years back. He sells excess to Duke about half the year. I think his break even was estimated to be 18 years but he was charting towards 14.

Leonard

With roof mount would want to put on new roof first. Otherwise roofer will want the solar off before he roofs it. In old days roof life was ~ 20 years, longer now. Also very easy to install ground based solar, no climbing.

Also leak potential for roof penetrations, mounting and wires. Get a good roofer to approve mounting plans. Dab of silicone rubber is not going to stick to a tar roof. Seen that with a sign guy, it falls off.

the_donut

Not roof mount.

GW

Thanks, I don't want roof; my home is sort of like a T, the south facing roof would be cut in half by the t, meaning one roof (the upper Right of the T) gets sun in the Am and the other south facing roof (the upper left of the T) gets sun in the Pm, hard to explain unless you sort of figured out what i trying to explain. My pay back is 7 years he claims. Evan at 8 it may be worth it

GW

I recall 20 years ago we took off thermal solar panels for the roofer. I almost want to cry at what i charged the home owner. Today's costs would be 10 fold!

the_donut

System come with battery banks I assume? What kind of storage capacity are you looking at?

Leonard

Even if they gaurentee the system to work past it's payback period. All seller has to do is go out of business and your gaurentee paperwork is only good to start your next woodstove fire.

I remember an old girlfriend paid $800 for a lifetime gym membership in ~ 1981 even though I said NO way ..... it's long gone

Make sure your not buying a rat that fails a lot. I'ld research the company and see if they have frequent failures, would think near by lightning stikes would be a risk to their electronic if they were not well designed/protected.

Fred

@GW, as part of the Landmarks Commission in my city, we are setting some guidelines for Historic Districts and buildings in our city. We have done some investigation with a few experts in the industry and on most occasions we have been told that they don't foresee prices dropping significantly, on a per installation basis but they anticipate more KW's per smaller panels and/or roofing shingles. I have attached a document from the National Alliance of Preservation Commissions as well as a draft set of assumptions/principals that I have drafted for some up coming working sessions. They are for Historic Districts but you may find them useful. I concur with you that they should not be on highly visable rooftops unless no other option exists.

Leonard

With ground based make sure windloading for the frame is calculated, it can be significant and require good cement foundations so it doesn't pull out.

Fred

Leonard said:

With ground based make sure windloading for the frame is calculated, it can be significant and require good cement foundations so it doesn't pull out.

Same holds true for roof mounted, except the mounting hardware is limited and when they pull through the roof decking and shingle, you also have the risk of water penetration into the home.

GW

Thanks all, this is not battery, this in on the grid. If power drops out then I have nothing.

Ok Fred if costs aren’t going to drop much I may just pull the trigger

Gary

FranklinD

I’ve been using solar for ~15 years now. I don’t sell to the utility, I run most of my garage off of it. I have about 800 amp/hours of storage at 24 volts and 4 - 100 watt panels on the roof. I also have a 10/2 run thru my extra conduit 40’ to the house to run boiler/lights/etc in case of a power outage. So far my 1500 watt sine wave inverter runs most everything I throw at it.

I’ve been looking at those individual panel micro intertie inverters too...may get into that with my next 4 panels. Prices around here for panels are at about 97¢/watt.

Leonard

With roof mount check HOW it's attached to existing rafters. Seen many installs of restaurant hoods/loads that hang from rafters of horizontal roofs. Contractor drills a 3/8 dia hole into BOTTOM of 1.5 inch width of wood rafter (tension side) and that weakens it. Rafters are usually JUST carrying the snow loads as it is in wood framing. So ends up needing a sister rafter installed. Mostly an issue near center of span (where bending loads are greatest).

Likely ok on top side of rafter ( compression side), unless have wind loads pulling roof upwards.

jumper

Labor costs won't likely decrease even if PV panels do.
I would not integrate PV with existing electric.
Inverters,batteries,switchgear complicate matters. I'd use PV to heat lots of water. Simple to store hot water.

Zman

jumper said:

Labor costs won't likely decrease even if PV panels do.
I would not integrate PV with existing electric.
Inverters,batteries,switchgear complicate matters. I'd use PV to heat lots of water. Simple to store hot water.

Hot water panels are much more efficient than PV.
If you are going to heat water, there is no need for electricity.

hot_rod

I think PV prices will start to creep up.

My metal supplier told me aluminum has gone up 30% since the first of the year! They expect 50% increase if tariffs are enacted. Other metals will follow probably. Boeing will take a big hit with those aluminum $$ increases. And Ford pickup beds

They are already seeing large jobs that were bid being postponed or canceled due to the huge cost increases.

FITS are disappearing in many European countries, I think in Colorado also. One German controller dumps excess PV output into a thermal storage tank, via resistance elements instead of giving it to the utilities for free. That works if you have a use for thermal in summer.

If you can get it up over 180F, you could run an absorption AC unit like they do with evac tubes in China.

hot_rod

weed your way through available incentives for MA here. A pretty good size list.

http://programs.dsireusa.org/system/program?fromSir=0&state=MA

jumper

Zman said:

Hot water panels are much more efficient than PV.
If you are going to heat water, there is no need for electricity.

Efficiency depends on how hot you want water.
Also thermal solar isn't so inexpensive when everything is considered.

GW

I think my nat gas hot water bill is $20 per month, I don’t think thermal is a good move. And, I’ve got two teenagers (not energy hogs, but still)

Gordy

Not a fan of PV. I would wait for panel efficiency to go up, way up. At max 21%. What that amounts to is a whole bunch more panels to get x amount of watts.

Plus the PV panels degrade over time unlike HW panels. 5.3 KW system today may only produce 4.3 KW in ten years.

Plus the system you were quoted has no storage.

How many KW a month do you consume Gary?

How much of the 30% tax credit do you get to use? I think it’s only 3k a year.

Brewbeer

I put up an 8.5 kW grid tie PV system 2 years ago, also in Mass, I used the outfit in Greenfield. While doing the math like you are now, the estimated break even point was 7.3 years. Two years in that seems about right, tax credits have been claimed and I get quarterly electronic payments from the renewable energy credit aggregator that are the size that the designer had predicted in his proposal. Mine is roof mount, had some needed roof repairs and new shingles put on at the same time.

You need to own to get the quarterly renewable energy credit payments, so if you are planning to move in the next 8 years, you probably won't see full payback.

Anecdote, my first house in Hatfield 20 years ago had non functional solar thermal panels on the roof, which I had to remove when i replaced the roof i that house.

hot_rod

Some of the motivation for installing RE is it makes you feel better, a bit energy independent. My goal is to offset most of my shop/ office AC load with PV

Or if you don't and forever wish you had... you can feel bad if that makes you feel better

GW

my last 12 months was about $1350. So I think the rough math is 535 KW/Month. When my two kids fly the coop that number will go down some. Yet there may be parents/in-laws coming at some point.

No storage--I didn't know storage was an option when you are on the grid. Maybe if it was boot-legged??

I believe I get the 30% right off the top, off my fed tax. That was the case when i did my geo install 5 years ago. it's as good as cash, practically speaking.

I don't use my geo much for heating. My AC bill is maybe $50 in the hotter months, just guessing

GW

Brewbeer, i think you mentioned that to me last year when i was asking about PV. I did talk with them, at that point they were too busy to come. They called several months later when I was cooled off. I like the guy I'm dealing with, Valley Solar, and a trades buddy had a bigger ground mount installed by them

Gordy

Yikes! .21 cents a KW.....

the_donut

In my neck of the woods storage is an on grid option, and so is selling back to utility. A transfer switch of sorts is used to determine when grid power is off to keep power from frying linemen.

hot_rod

Some of the new hybrid inverters are grid tied and also allow some battery storage. Battery technology gets better all the time, not sure how that Tesla battery bank is working out?

I suspect energy costs will climb, how much how fast is anyones guess. So predicting long term ROI is a bit cloudy.

Since you are capable of doing the install and buying at cost, maybe a solar thermal collector or two and a dual coil tank would be the best bang for your buck? I have some solar thermal parts if you want to go that route. And a drain pipe recovery tube

Doesn't look like you use a lot of energy of any type, so calculating return on RE may not show the numbers you expect.

Getting back to that feel good rational

D107

About roof leakage here's a sampling of some web comments: ..."Photovoltaic mounting components are specifically designed for rooftop solar installations, and thus guard against roof leaks. Special flashing is installed around every rooftop penetration to help water flow safely away. To ensure a watertight seal, the holes are filled with high-quality silicone..." Another one said that they use licensed roofers to pre-inspect, then waterproof and seal the PV areas of penetrations, not the electricians who install the panels.

Also "A simple way to avoid roof leaks in the first place is to mount the structural supports directly on top of the felt paper. We then apply polyethylene caulking directly to the lag before we ratchet it into the structural member. We also apply a polyurethane sealant to the base of the stantion support. On asphalt shingled roofs, we use a type of roof jack that is basically a piece of corrosion-resistant sheet metal formed to slip over the mounting stantion. The base of the flashing rests directly between the roofing materials. This allows the water to flow down the roof without leaking into the house. We use a punched roof jack instead of a seamed jack because this provides another level of protection against leaks. We seal the area where the mounting post protrudes through the roof jack with polyethylene caulking."

Then there's maintenance: "Not only do I have solar panels on my own house, but I wash my panels four times a year. At minimum your panels should be washed annually. Smog and dirt particles in the air create a sticky grime that does not come off with rain. In addition, dirt and grime tend to collect in the ridge between the tempered glass on the top of a solar panel and its frame. This buildup degrades the power output from the panel. We find that washing panels can increase output by 2% to 5%."

If you have a high roof that you have to hire someone to clean, that's a cost worth considering.

"Sealant by itself has poor long-term waterproofing reliability, but when used in combination with manufacturer-approved flashing methods it can provide decades of reliable performance. Sealant is typically applied into all pilot holes and under the flashing around the lag bolt hole.

There are several common sealants used in rooftop solar installations, and it is crucial to verify sealants are compatible with the roofing, flashing seal and any other materials they contact.

Asphaltic roofing cement (mastic) with reinforcing mesh is a code approved method for sealing underlayment flashings below tile, and it is also used as sealant on shingles, but most solar installers rely on roofing sealants like those from Chemlink and Geocel. These synthetic sealants can provide decades of performance when properly applied. Each sealant is unique in its performance characteristics. Some sealants can cure underwater while others prefer dry application. Some can handle temperatures over 200°F while others should never be used in areas with full sun exposure. Research is important to make sure the sealant can last the life of the roof and array."

jumper

Problem with selling back to grid is that somebody has to pay. Eventually those ratepayers will wise up. Or too many sell back to grid and price goes negative. As it already does sometimes in California.

Leonard

Flat roof. To seal roof penetration Electrician put a rubber "witch hat" shaped cone on roof, used tar flashing cement to seal it down to roof, and cut cone to match dia of conduit he ran thru it. Rim of cone "hat" sitting on roof swelled up and bucked upward. Made a finger sized tunnel that water POURED in thru when ice dams started to melt.

Talked to a roofer and found rubber those are made of is not compatible with oils in roofing tar. Guess it's not neoprene. Check everything with a good roofer.

He also didn't think much of those aluminum ones for angled roofs with a rubber domed seal. Seen them leak at our building.

Roofer said a good conduit penetration for hot mopped roofs is a copper tube soldered to a wide base, tared to roof ,then tube filled with tar. Bit more complicated than a dab of caulk

D107

In terms of PV efficiency limitations, this article holds that 20% is adequate, especially considering it's a renewable source, compared to similar efficiency for gasoline in cars. https://dothemath.ucsd.edu/2011/09/dont-be-a-pv-efficiency-snob/

GW

On the roof: yes that’s a whole different topic right? When the shingles start giving up that’s a whole different set of costs. I’d like to be a fly on the wall with some bogus installers lay systems on poor roofs (and the roofers show up 5 years later)

In my plumbing days, I’ve sent holes and pipes through the roof hundreds of times. It’s so simple a plumber can do it. Some birds have no clue though. I’ve had a couple of employees that “didn’t know”.

Larry Weingarten

Hello, I have a client/friend who asked about installing PV. We started by making his house more efficient. Mostly with refrigeration and lighting, took 70% off the usage! Now his solar will be far less expensive. I second what Hot Rod said about getting an inverter that can deal with power outages. I think Midnight Solar and Outback both make such inverters. As to the roof vs ground mount debate, ground mount simply has less to go wrong... no finger pointing between roofer and solar guy when there is a leak. If you must go with roof mount, use roof jacks and for the racking, use Kee Klamps or some similar approach that lets you remove the panels and racking easily when re-roofing.

Yours, Larry

Gordy

David107 said:

In terms of PV efficiency limitations, this article holds that 20% is adequate, especially considering it's a renewable source, compared to similar efficiency for gasoline in cars. https://dothemath.ucsd.edu/2011/09/dont-be-a-pv-efficiency-snob/

20% efficiency means the panel, or array has to be 80% bigger to get x amount of watts. I Could care less about the source of energy being renewable.

Leonard

Read in engineering magazines few years ago ~ 18% was cutting edge state of the art. Check what % your systems will be. used to be 10-15%. Cheap solar might be old low % stuff

Gordy

My point is a typical 5.3 kW array Is around 20 panels.

If efficiency was even raised to 50% you would only need 10 panels.

That frees up space for a bigger array, and should cut down on installation costs. Also less material in panel costs.

Gordy

The technology exists to have 38-46% efficiencies.......

invermont

I have a solar company down the road from me. I occasionally talk it up with those guys. I’d do some research on this company that comes back that much cheaper with only an eight year payback. Do a lot of research before you dive in. If it sounds to good to be true...................

hot_rod

I prefer ground mount PV also. Roof mount voids some shingle warranty, firemen don't like large roof arrays, and penetration leak potential.

With ground mount you could manually or automatically track one or both axis to maximize the array. Easier to clean modules on the ground mounts, maybe less obtrusive to neighbors. Some subdivisions CCRs prohibit roof mounted stuff.

Typically it pencils out cheaper to add extra modules compared to complex, expensive trackers. But manually twisting and tilting a pole mounted array could be a less $$ option.

PV with micro inverters is super simple to install yourself, screw the small box on back of the module, plug into the harness, a labeled disconnect on the outside of the building feed into a breaker in the panel.

Your utility, like mine will probably want a licensed electrician to sign off on the design and install. I did my mounting and wire pulling, then electrician kept all the interconnection code legal. Micro inverters make data logging easy also, a simple box monitors individual modules and total output.

Solar thermal on roof mounts to eliminate under ground piping. In winter months ST is fairly low grade energy, don't want to lose any in underground pipes