# Solar Roof



## warrior4 (Oct 16, 2013)

So I just saw a video on Facebook about how the Tesla company has a new solar roofing system they've designed. The solar panels have a film on them that makes them look like normal shingles or roofing tiles and feeds into their Power Wall concept. The video claimed that it has the potential to provide all of the power needed for a normal home. Anyone else have any thoughts or ideas about this? Just curious is all.


----------



## Camel923 (Aug 13, 2014)

I saw that a few months back. I like the concept. Solar energy while not advertising the fact you have solar energy. The idea has merit. My question is how much energy does it really produce? For winter and night would it be wise to harness the wind but there goes the stealth factor.


----------



## Slippy (Nov 14, 2013)

I love the concept but here's some of the problems;

First, roofers are not electricians and that poses a problem with the install. Second, and I may be wrong but Tesla is all about the Battery System right? I have no doubt that if anyone comes up with the best solar battery it will be Tesla but how much does the battery system cost and how much does the roof cost?

Roofing Materials are pretty cost effective. I have a 50 year metal roof on my house that will not only outlast me, it most like will out last my children since 50 years is the warranty and metal roofing materials are known to last a hundred years.

I have no idea the cost of the Tesla roof but I'm guessing this will be most likely 15 times the cost of conventional roofing materials. Can you get a payback on this or is it like most solar systems and the break even analysis is just not there.

Might be more practical to set up your own solar panels and off grid battery system and when Tesla comes up with an affordable battery replacement for conventional batteries, you just buy that.



warrior4 said:


> So I just saw a video on Facebook about how the Tesla company has a new solar roofing system they've designed. The solar panels have a film on them that makes them look like normal shingles or roofing tiles and feeds into their Power Wall concept. The video claimed that it has the potential to provide all of the power needed for a normal home. Anyone else have any thoughts or ideas about this? Just curious is all.


----------



## paraquack (Mar 1, 2013)

I'm in the process of looking to buy a solar roof system. Problem is most people run a 480 Volt DC system to their inverter/grid tie. I'm looking for something I can utilize for a grid down system too. If any one knows about a solar roof system like this let me know, PLEASE.


----------



## 8301 (Nov 29, 2014)

@paraquack Solar roofing tiles usually run about 4.8v at about 7 amps per tile so you can make each string as long or short as you want changing the voltage up to the maximum voltage. Example, if your MPPT type inverter has a maximum input voltage of 150v and you put 28 of these 4.8v panels in series you will end up with 134v output at 7 amps. This is one "string" making about 940 watts. Using 3 strings and combining them in a combiner box gives you about 21 amps at 134v or 2814 watts in panels that then is sent to the properly sized controller. Or you can go much smaller. Using a MPPT controller you want the string voltage to be at least twice the battery bank voltage.

I've never used solar roofing tiles but from what I understand they snap together to complete the electrical connection and you want to be careful to protect the water tight seals. The largest downside to solar tiles is if one ever goes bad you can't simply unplug the wires from each panel for testing.


----------



## Targetshooter (Dec 4, 2015)

I looked into getting solar , no way now . It's just to much trouble to deal with for me . jmho


----------



## stowlin (Apr 25, 2016)

The only serious draw back in the cost. I am kind of a tesla fan (have a bunch of stock in it) and Elon makes all kinds of announcements to promote his company; momentum is huge in his world (tech) so he tries to stay important even when his next car is still 11 months away from delivery. The solar roof idea is not cost effective and the only thing driving the success of solar is states that regulate the cost of electricity to the point where solar after rebates costs less. Solar does not work where electricity is affordable. Some CA' residents will pay .35 cents a kilowatt hour for electricity and solar can be installed at a 20 year cost of about $.20 so it makes a lot of sense for them. I understand most places don't charge anywhere near .35 and the solar roof I heard was likely to cost .75 a kilowatt hour - so its not for the mainstream yet.


----------



## NotAnOxymoron (Jan 7, 2017)

I'm obsessed with the concept, skeptical of the reality.

It seems to be a hot topic with firefighters right now. It'd definitely complicate their jobs.


----------



## 8301 (Nov 29, 2014)

Stowin has it figured out. There are lots of ways to figure it and in a few cases solar makes sense financially if that is your only concern. Other reasons to put in solar are short term grid backup, hobby value, and long term SHTF power. The fact that solar does produce value lowers it's cost if you are willing to invest for the long term payback but in most cases even well designed systems don't totally pay for themselves financially. However in my case the hobby value and long term SHTF value makes it worth it. And in my case the system is efficient enough that it should come very close to breaking even financially. A lot depends on how long a set of expensive batteries last and local power costs.

The best way to reduce your power bill is serious energy efficiency around the home. typical evening lighting below.
eight 60 watt incandescent light bulbs = 480 watts or...
eight 60 watt equivalent florescent bulbs = 108 watts or...
eight 60 watt equivalent LED bulbs = 37 watts 
add satellite TV, fridge and chest freezer, porch lighting, this computer and this place uses about 240 watts (2 amps at 120v) most evenings.
And for short term power outages a decent quality generator is probably a better financial choice.


----------



## 8301 (Nov 29, 2014)

NotAnOxymoron said:


> It seems to be a hot topic with firefighters right now. It'd definitely complicate their jobs.


NEC 2014 solar electric requirements require that all power cutoffs be easy and fast to disconnect for firefighters.
NEC 2011 makes 90% of all power disconnects be easy for firefighters to find and disconnect.
It's the older installs that may or may not have disconnects within 10' of the home's power meter.


----------



## RJAMES (Dec 23, 2016)

The only issue/ problem is the initial cost if you can with a combination of loans, rebates, sell other investments to raise the funds to obtain a system you should in my opinion. 

In some areas of the US you can power your home and car with solar. It cost but then you do not have to buy gas for the car at 40.00 a week or pay an electric bill at 4-500 a month. Grid tied systems are now obtainable to most Americans.


----------



## 8301 (Nov 29, 2014)

RJAMES said:


> The only issue/ problem is the initial cost if you can with a combination of loans, rebates, sell other investments to raise the funds to obtain a system you should in my opinion.
> 
> In some areas of the US you can power your home and car with solar. It cost but then you do not have to buy gas for the car at 40.00 a week or pay an electric bill at 4-500 a month. Grid tied systems are now obtainable to most Americans.


Stowin in post #7 got it right. While close financially in many areas (like mine) going with solar (especially solar with a battery bank) is usually not financially justifiable if financial is you only reason for solar. This is especially true if you take a loan out to pay for it or want power when the grid goes down (batteries).

If you live more than about a mile from any power lines solar makes sense. Even the "sell to the grid" packages may be in trouble because most utilities are raising their meter fees and reducing their purchase prices as the electric grid is becoming close to being saturated with too much solar on sunny days. Even on strong solar days power companies must use generators to keep much of the power in the lines to establish the HZ cycle for solar inverters to match up to. And power companies must maintain enough generation capacity to handle weeks of low solar input. It is expensive to maintain power plants that aren't putting out much power during sunny days so the power companies have to take that expense into account when determining how much solar power they can accept.

My original plan was to keep a small battery bank and sell excess to the grid but the local utility announced that they were doubling meter fees about 14 months after my system would have gone online so I never wired to sell to the grid. Instead I took a more expensive route, increased my battery storage and installed a mini-split so I could burn the excess solar power I was producing. I still have the clothes dryer and electric stove hooked to the grid so my electric bill is about $26/month. But this allows me to keep grid power to the home if we go through 3-4 days of heavy clouds. Just flip a switch and grid can power my home, something I do 2-3 times each winter.

By the same token when we lose grid power for a day or two (not unusual where I live) I never even notice until I notice the clock on the stove is off.


----------



## csi-tech (Apr 13, 2013)

I just ordered two 100w poly panels with a solar charger/controller and associated connectors and wires. I am debating whether to just mount them on the roof of my RV or set them up on the ground. I think I can store them in the camper and buy the 40.00 stands. Should only take a minute to set up.


----------



## bearsergeant (Jan 28, 2017)

Are there benefits to having solar panels on the roof versus on the ground? I ask as I have about an acre of cleared land behind my house.


----------



## Michael_Js (Dec 4, 2013)

we're looking into solar, but not yet as we just bought our house. On the ground provides adjust ability and access. They say moving them 1 degree up/down depending on the season makes them more efficient - don't quote my numbers...Unless you add motorized sun tracking devices, IMHO, the ground is better. that's what we're looking into...

Rebates go away soon though in WA - I think next year...so...

peace,
Michael J.


----------



## stowlin (Apr 25, 2016)

Solar panels really need a specific azimuth to the sun. If your roof is not 178-185 degrees to the sun (the azimuth) then ground can be better because you can set your grid to the optimum azimuth. However you have to avoid shade too, for any shade will kill the panels out out.



bearsergeant said:


> Are there benefits to having solar panels on the roof versus on the ground? I ask as I have about an acre of cleared land behind my house.


----------



## 8301 (Nov 29, 2014)

stowlin said:


> Solar panels really need a specific azimuth to the sun. If your roof is not 178-185 degrees to the sun (the azimuth) then ground can be better because you can set your grid to the optimum azimuth. However you have to avoid shade too, for any shade will kill the panels out out.


On the azimuth while it is always better to point them due south with panel prices getting so low a lot of people are mounting with less than perfect roof orientations. Between 150 and 210 degrees is acceptable with a few extra panels. Other people mount most panels directly south but put a string of panels somewhat eastward to catch the morning sun and somewhat westward to provide more late in the day power. My ground mount is perfectly south facing but since I now run the AC and heater off solar (mini split) I'm considering adding a string (four panels) to the SW facing roof to provide another 90 minutes of solar late in the day.

Panel tilt should be the same as your latitude for maximum year round performance. If you tilt the panels a little steeper you will do a little better in the winter and snow is less likely to cover the panels. Way up north a few people mount the panels vertically on a south facing wall to keep snow off them and maximize winter solar gain. Not as efficient as a panel tilted at 35 degrees but better than a snow covered panel.

Now days you can get panels with mini-inverters attached to each panel to maximize output as some panels become shaded.


----------

