Solar Power DC Metro, Northern Virginia

Solar Quotes
1

I would like some help deciding what makes sense for our installation. We need a new roof [soon - ours is >30 years old but we currently have no active leaks], and our federal solar tax rebate starts cutting back next year, so we are in the market for both a new roof and solar.

I have in-hand solar proposals from two local companies. I asked each company for 4 quotes - two optimal (the # of panels they recommend), one quote using a ‘good’ panel and one with a ‘premium’ panel, and two maximized (if we installed an absolute max number of panels) – also good vs premium panels. Both came back with LG Neon R or Neon 2 for the premium panels; one recommended Hanwha Q-Cells as the ‘good’ panel and the other’s alternative was Silfab SLA-M panels.)

The differences in their proposals are striking and interesting: one company proposed 16 vs 25 panels (optimal vs max, 5 vs 9kW system), and the other proposed 37 vs 56 (11 vs 18kW system)! Also, the azimuth and roof pitch reported each proposal is very different. Azimuth varied by ~25º and pitch by ~20º. Our house/front roof is oriented ~160º south (according to my iPhone), and is about 40% shaded by trees in the spring/summer/fall. The front roof is steeper than the back roof.

So… I have a LOT of questions:

  1. Does the difference in azimuth stated in each proposal matter very much to the calculation of how much energy we will harvest? What about the pitch degree?
  2. Why/how could each company recommend such differently sized systems?!
  3. I don’t see anything about Silfab panels on your site, although their panels did well in the PVEL tests.
  4. How do we choose between the different panels proposed? Are Hanwha Q-Cells better at managing collection in shady areas, better for our roof than the longer-warranty of the LG Neon-R or Neon-2?
  5. How much tree-shade is too much for a panel to harvest sun?
  6. If we go with LG, how do we choose between Neon-R vs Neon-2?
  7. Does it make sense to cut down any trees to maximize solar? We are very reluctant to do that…
  8. How much does panel wattage matter?
  9. Does panel weight matter?

Then there is TESLA…my husband thinks we should consider signing up and waiting for their glass tiles - do they manage shady areas well? (I can’t find any technical information about them.)

2

Hello my lovely aunt :blush:

Thanks for posting, great questions! I will get to them all, but first I think we’re missing the most important part of the system, the inverter. Have you got details of what inverters they are proposing? Given your roof shading, I am hoping they are proposing to use Enphase micro inverters. We have details on Enphase here, and why micros are better in your situation:

Also given your shading issues, I would recommend the LG Neon. We have an article on the difference between the models (see below). @Svarky could you clarify the difference between the Neon 2 and the Neon R? Looks to me like the Neon R has a higher efficiency, but Neon 2 may offer better performance in shade? LG Neon and Sunpower Maxeon are really head and shoulders above others in terms of performance in shaded areas. That may be a slightly annoying answer given they are certainly the most expensive option, but I think worth it.

We don’t get much Silfab panels in Australia, so don’t have feedback on that, but LG Neon will be a better bet than Silfab or QCells with shade.

It’s surprising that the installers had such different measurements of pitch and azimuth. It might help in deciding which installer is more competent, by finding out what your actual pitch and azimuth is and seeing who was closer.

Wow, they really are very big differences in system size that they proposed. Please see the chapter in our Guide to Buying Solar on How big a system should I get, that should help you work out which size is more appropriate. Let us know if you have further questions. It would be useful to know how many kWh you use per day on average (should be on your energy bill).

Regarding the tree shading, it’s hard to give feedback on that without seeing the site, or aerial images throughout the year. From memory, there’s a lot of beautiful trees, don’t cut them down! If anything, reduce the system size so that you can install panels just in the area on the roof that has minimal shading. Given you have deciduous trees, I would have thought parts of the roof that have good sun throughout the day in the summer months should be fine to put panels on. They may get partial shading during autumn/winter, but the micro inverters and Neon panels will help to still get decent generation.

Panel weight and wattage don’t matter in short. It’s really about the overall size of the system. However, if you do find that you have limited roof space to use, efficiency may come into it, because you can get more panels in less space. It’s really not going to make much of a difference though, especially if you are choosing between Neon R and Neon 2. A 2% difference won’t make a big difference in what you decide. If you want more info on that, we have an article on panel efficiency here:

Good luck, and please keep us posted with your progress.

Marty

Solar Installers Northern Virginia

Some other installers that have good reviews on the web are:

  1. Nova Solar, Inc. | Falls Church, VA
  2. Ipsun Solar | Fairfax, VA
  3. SolarNova | Hamilton, VA
  4. Continuum Energy Solutions | Alexandria, VA
  5. Prospect Solar LLC | Sterling, VA

Find solar installers in your area

1 Like
3

Oh, I nearly forgot - Tesla solar tiles. I am sorry, we don’t have much info on them. I would avoid just for the reason that they were announced so long ago (2 years?) and still don’t seem to have come to fruition. I doubt they will be cost effective, and being so new you won’t be able to find reviews on them, especially not on how they perform over time.

4

Thanks Marty! All this is very, very helpful and I’ll read further today.

One proposal does indeed recommend Enphase micro-inverters, the other SolarEdge. And in my reading more yesterday I saw your articles and came to the same conclusion that Enphase will be better in our environment.

Regarding Tesla, as you know we LOVE our Model S, and after reading the book “Elon Musk…” by Ashlee Vance, I am even more impressed and amazed by his vision and determination, so I expect their solar tiles are, or will be, way ahead of current technology. BUT, as you suggest, it could be another 2-3 years before all the kinks are sorted out. So…dang! :woozy_face:

Looking forward to reading more on your fantastic site!

Linda

5

Here is a photo of our site (with the most conservative panel proposal):

HouseSatellitePhoto
HouseSatellitePhoto.jpg670×670 229 KB

How do I find out our actual azimuth and roof pitches?

I don’t know what month that photo was taken, but most likely in winter because trees are leafless. Regarding LG Neon 2 vs R, I can’t tell from the review article on your site which panel would be better for us so hopefully “Svarky” will have some info. If we go with R, is it worth waiting for the 380w panels?

Regarding system size, 5kW seems too conservative to me, and 18kW doesn’t seem like too much. Our utility will buy back (allow us to net-meter) up to 20kW per month. Based on this photo and other info I’ve provided, what does it look like to you could be our max size? I would like to max it out, but don’t want to be foolish! And of course perhaps we won’t be able to afford to max it out…

Linda

6

Good to see the solar companies over there are using Nearmap for aerial imagery, a good Australian company which has made their shareholders pretty happy over the last 2 years :wink:

Looking at that image, I can’t see how you would be able to get more panels than that on the roof whilst maintaining reasonable performance. The north roof just won’t get enough sun, and the western part of the south roof looks too shaded. Even those 16 will be a squeeze. (So other readers don’t get confused, I should point out that you are in the US).

If you use the LG Neon 370W, that will give you nearly 6kW of panels. A couple of points on this:

  • Having looked into this further, the Neon R is the way to go, they are the latest and greatest and handle shading as well as the Neon 2. The extra efficiency of these panels will help given your space restrictions.
  • 6kW is a perfectly big solar system. In fact 5 years ago, it would have been considered enormous. It will generate about 20-25kWh per day (I’m having a guess at how much sun you get), which is quite a lot of energy. I would be surprised if you use much more than that. To give you an idea, in our two and a half person flat, we use about 5kWh a day (a 1.5kW system would be more than enough for us to generate all the power we use).

Could you please link to their policy on this? It gets a bit confusing when we talk about kW and kWh. To simplify it, kW is the generation capacity, and kWh is the amount of energy produced. So, if they are saying 20kWh a month, that is actually a tiny amount, it would be less than a 6kW system could generate in a day.

7

Thanks Marty! Here is the link to our utility on net metering: https://www.dominionenergy.com/home-and-small-business/renewable-energy-programs/net-metering/net-metering-faqs

8

Ah ok, so this looks like the relevant section:

So you would be able to install a massive 20kW system, which would produce around 70-80kWh of energy a day on average.

I don’t think that changes much though from my last post, I don’t think there’s much you can do by way of getting that much solar on your roof, nor do I think you’d need it.

It would be useful to know your average usage per day though (should be on your electricity bill in kWh).

Marty

9

I forgot to include our utility usage…our bill doesn’t state an average but gives us a 13-month history, so I calculate our past year’s average to be 1600kWh/month. Would that then be about 53kWh per day? The vendor says a 5.7kW system will provide about 35% of our usage. Does that sound right?

10

Yep that sounds right. 53kWh is a lot higher than I expected. In that case it would be good if you could get more panels up there, but I’m just not sure where they would go.

I guess you could consider some tree trimming in order to be able to cover the south roof and get 12kW, which would close to cover your usage, however it looks like you’ve got something else on the south roof also?

11

We’ve started talking about how to reduce our electric usage. Those are skylights you see on the south end of the roof. :blush: And we will consider removing branches or even a tree if it’s near end-of-life to allow for more panels. The vendor says once we commit a much more detailed engineering plan will be done and may recommend more or fewer panels.

Our question for you: given our roof/environment, does it really make sense for us to do solar? Initial estimate shows payback in 25 years.

Linda

12

Well that’s a whole other question. In Australia the payback period is usually very short (a few years or so), and therefore financially a no brainer. I know systems are consistently a lot more expensive there for some reason.

I’ll need some details to see if that 25yr payback is ballpark. What is the quoted price for the ~5kW system? How much do you expect to get back from tax credits? How much do you pay per kWh for your electricity (let’s say peak pricing).

Marty

13

Quoted price is $22,404 for 5.92kWh system.
Tax credit will be 30% so net price will be $14,297.
Our price per kWh average is 11.04 cents, but I can’t find the
peak rate.

  We are also considering the Tesla Powerwall ($12,000 installed,

minus 30% rebate)…good idea or not? We do have a lot of
power hiccups and outages.

  Linda
14

Mmm, that is quite dear, and electricity quite cheap compared to Australia, so that does make it a difficult equation. I’ve never understood why solar is more expensive in the US (before rebates), everything else is cheaper there.

@Ekelly234, you are based in Virginia right? Can you give some feedback on whether $22k is a ‘normal’ price for say an Enphase and LG Neon system? That’s really as premium as you can get, so it does bump the price up. Linda, Ed Kelly is an installer based in Edinburg, he’s been a contributor to the forum for a while. I’m not sure how far that is from you, but he might be able to offer a quote http://www.shenenergyservices.com. Although, I seem to recall that Ed does not work with micro inverters generally.

As for the payback, I think you would get at least 20kWh a day on ave, so lets use that assumption:

  • 20kWh/day x $0.11 (electricity cost) x 365 days = $803 savings per year
  • $14,297 upfront cost
  • $14,297 / $803 = 17.8 yr payback.

Yep, it’s a pretty long time. That’s quite disappointing actually, no wonder there is a lot less residential solar in the US that Australia. I guess it’s up to you as to whether it’s worth it. I would do some shopping around to see if you can get a better price, I can’t understand why it would be so expensive, but that does seem consistent with other US quotes we’ve seen.

I should mention that Enphase isn’t your only option for panel level optimisation, you can get very good shade performance with SolarEdge or Tigo optimisers. You could also look at some of the other lower cost, but still quality panels on our Best Solar Panels list:

I think the Powerwall is a separate consideration to the solar. It’s not something you would do for financial reasons, or environmental reasons, it is simply if you would like some energy security if your power goes down. I personally wouldn’t consider it, but it depends on how important it is to keep to power on for you I guess.

Marty

15

Linda
This is way too high

I would recommend against the power wall and this is way too high

Where are you located?

16

We are in the DC metro area, in Northern Virginia - I would appreciate a third quote. We have an even higher quote from another company.

17

We don’t go to DC area

18

Ah well! :smirk: Too bad. How much too high do you believe our proposal is…what should we expect instead for the NoVa area?

Thanks

19

I would say about 3 20 a Watt and don’t get the power wall
Also try standard solar their up in your neck of the woods

20

Thanks - I contacted Standard Solar, but they no longer do residential installations, but I will reach out to others for additional quotes. And do you mean we should pay about $3.20 per watt for the installation, so for a 5kW system, 5000 x $3.20 = $16,000?