2014 Solar Report

Solar 2014

We just finished our first full calendar year (i.e., January to December) with our solar PV system and it was a great one. Renovus (our solar installer) gave an amazingly spot-on estimate: they (well, their software) figured our 12-panel, 3.92 kW system would produce 4494 kWh per year. As you can see we got 4434 kWh this year. Less than 2% off.

I had some perceptions that didn’t meet up with reality. For example, I felt this summer was unusually mild and much less rainy than 2013. It also seemed like we enjoyed a warmer and sunnier September too. The data doesn’t bear that out. August 2013 was the first full month the solar system was in operation, so comparing from that point onward you can see that 2013 outperformed 2014 in every month except December.

2013 2014
August 523.53 513.01
September 478.46 472.33
October 319.27 303.06
November 244.93 198.84
December 66.72 88.08

I’m pretty happy that 90% of our electricity needs are met by solar, but I obviously want to do better. We have 300 watts of kitchen recessed lighting that gets used a lot (at least 2 hours a day; likely more) and still hasn’t been switched over to LED. I have a bunch of vampire devices like the Playstation 3 and Wii that don’t get used much but waste energy nonetheless. There’s more we can do to keep moisture out of the basement which would allow the dehumidifier to run less often. I’d love to get to 95% in the next year.

I can’t neglect to mention that we may have increased our usage by having central air conditioning installed this past spring (also by Renovus; they recently added HVAC to their list of services). I still need to write about that. Before that we relied on several window units. I haven’t done any work to compare the electrical load of central air against 3 window units, but according to our NYSEG bill there’s no doubt we used more electricity:

Billing Period Average Daily Use Average Daily Temp
July 2013 7 kWh 73° F
July 2014 7 kWh 69° F
August 2013 9 kWh 65° F
August 2014 14 kWh 65° F

So despite a warmer July in 2013, we used the same amount of electricity in 2014. And despite the same average temperature in August, we used 50% more electricity this year, though this comparison doesn’t quite work since in 2013 we were away for 10 days that month. Still, it’s probably safe to say we’re paying for that extra comfort.

Solar Monitoring Downtime


In my last post I discussed one of the dangers of cloud resources: if the company goes under, so does your access to their data. But even when the company is alive and well you have to suffer with their infrastructure deficiencies.

SunPower monitoring has been unavailable for over 18 hours now. When their servers are down, the system at home can’t upload its data and I don’t know how much history it can cache. Hopefully when the servers are back up I will have not lost any information. The only way to see production data now is to use the LCD on the inverter (I could set up a webcam pointed right at it!). Consumption data can’t be viewed locally at all.

My preference would be for the monitoring equipment to run its own server. You could view the data on your LAN even when your internet connection is down, and with an open port you could monitor your system remotely too. I’d also be OK with some kind of hybrid solution, where the data is viewable locally but is also uploaded to SunPower’s servers. There’s probably no chance we’ll get anything like this.

Even when their equipment is up and running the website and app are intolerably slow. HD video is faster to load. I’d be happy if they just took this downtime to improve their servers’ performance or increase the bandwidth on their connection. I’m not too hopeful on either of those.

Solar Sign-off

This morning someone from the city came over to inspect the electrical work that Kenny Broadwell and his team did in preparation for the solar system installation. Since they arranged the inspection, Dakota and Keith from Renovus Energy took the opportunity to stop by and give us a final walkthrough of the solar system.

Dakota congratulates me for our system generating over 20 kWh yesterday
Dakota congratulates me for our system generating over 20 kWh yesterday

They presented us with a binder full of information: all the documents I signed, schematics of our system, the spec sheets and promotional materials for all the equipment, warranty information, and the manual for our inverter. Dakota pointed out that besides providing a record of all the work done, the binder is great for showing off the system to friends and family.

The cover features a photo of the system from the roof, much closer than I'll ever get to them.
The cover features a photo of the system from the roof, much closer than I’ll ever get to them.
Schematic of the system
Schematic of the system

Dakota then walked us through all the information displayed on the inverter’s small LCD. I had already browsed through the manual online to learn the meaning of most of the data displayed, but some things, like the individual power output of the two arrays (two arrays of six panels each) was new to me. He noted, for example, that a big discrepancy in output between the two panels might indicate a problem with one of the panels. He went over a couple scenarios in which we might need to power cycle the inverter or monitoring system to resolve small issues. He noted too that the inverter’s measurements could be ±5 kWh from the actual while the mechanical meter could be around ±3 kWh (if I’m remembering that right).

Of course, we don’t expect to spend much time in the basement looking at the equipment given that the monitoring equipment lets us check most of that data in easier-to-read, prettier output on the SunPower website or via their iOS app. We briefly discussed my fear that SunPower will go out of business and make our monitoring data inaccessible (since all data is uploaded to their servers before being made available to clients). There’s not much we can do in that scenario besides a.) reverse engineer the protocol to build our own replacement server, b.) replace the monitoring equipment with a third party option, or c.) understand that remote monitoring is a luxury we can do without. I get “c” pretty well, but damn I love looking at the data. More on monitoring in a future post.

So… that’s pretty much it. Apparently the city inspector has some things to go over with the electrician and NYSEG still has to put in a new meter to enable net metering. But since we’re already generating power and feeding electricity into the grid, most of that stuff is gravy.

The Cost of Solar Photovoltaics

One of the first questions I get about our solar photovoltaic system is about cost. While details vary by system size and details of the house, I thought it would be useful to share what it cost us. I mentioned before that we got the top-of-line panels from SunPower, so keep that in mind when examining these numbers. Also, as you’ll see, I don’t have the cost of individual components such as price per panel, or price for the inverter. These are the numbers that Renovus gave me in roughly the same format they gave me. At best this might give you a template for a very rough estimate.

Description and Quantity $/ea $
Solar modules SunPower E21 series, SPR-X21-345, 345W high-efficiency solar modules: 96 back-contact cells, white backsheet, 21.5% panel conversion efficiency, 19W per sq.ft. peak output, 25-year product and power warranty. SunPower Package-3 12
Inverters SunPower SPR-4200p-TL-1, 4200W, 208/240/277VAC inverter, dual Maximum Power Point trackers 1
Mounting systems UniRac SolarMount-I PV mounting system, 6005-T5 aluminum extrusion components, PE-certified, 10-year limited product warranty, 5-year limited finish warranty. Aluminum/stainless steel waterproof asphalt shingle roof flashings. 1
Monitoring SunPower Monitoring System for 1 SPR-xxxx inverter. Includes SunPower Data Loggers, SunPower Gateway, SunPower Wireless Display, Smart Monitoring Web Interface for homeowner and dealer, cabling, power supplies. 1
$1,198.88 $14,386.50
Electrical BOS Electrical balance-of-system for roof-mounted PV system – including as needed: wiring, metering equipment, conduits, safety disconnects, wiring enclosures, AC/DC load centers, electrical protection devices, safety signage, inverter accessories. 1
$2,473.50 $2,473.50
Materials Total $16,860

Labor is another $6,880 for a total of $23,740.

But then the rebates come into play. Renovus takes care of the NYSERDA rebate, which at the time this system was designed was $1.40 per watt. Our 4140 watt system (12 panels generating 345 watts each) therefore qualifies for $5,796 that gets cut off the cost listed above without me having to worry about it.

Then there are the New York State and federal tax credits. Both are based on the cost of the system after the NYSERDA rebate is deducted. That’s $23,740 – $5,796 = $17,944. The New York State tax credit which returns 25% of that number for a return of $4,486. The federal tax credit gives back 30%, for $5,383.

So in summary:

Cost of the system $23,740
NYSERDA Rebate ($1.40/watt) -$5,796
NYS Tax Credit (25% after rebate) -$4,486
Federal Tax Credit (30% after rebate) -$5,383
Our cost after filing taxes next year $8,075

When do we earn that cost back? It’s hard to say with lots of variables like the amount of electricity that we actually generate (which is dependent on things like how clear the skies are) and the cost of electricity in our area. Renovus estimates we’ll generate about 4800 kWh/year. If the cost of electricity stays at 15 cents per kWh forever, we’ll recoup the cost in a little over 11 years. Renovus’ projection takes into account historic rises in electricity rates so they estimate payback in under 9 years.

That’s all well and good, but it’s not all about recouping the cost of the system for us. We’re using less coal- and natural gas-produced electricity and we feel good about that.

By the way, in case you’re not familiar with how tax credits work, they’re not just cash given to you by the government. They’re credit towards tax that you owe. So a.) your tax liability has to be at least as much as the calculated credits for you to take full advantage (I think you can carry over excess credits to the next year, but I’m no expert on that) and b.) you don’t get that money until you file your taxes, which for us will be around April 2014.

With the monumental number of expenses we have from buying and fixing up a house, we don’t just have $9,869 (the total of the two tax credits) that we can afford to have tied up while we wait for next year. Many solar installers work with Enerbank (maybe other outfits too) to give their customers same-as-cash loans that remain interest-free for about a year, giving the customer time to get their tax savings and apply it towards the balance. It’s a great way to capitalize on solar savings early without locking up lots of cash.

One final, very quick note: solar leases are pretty popular. Their low or no cost to entry is attractive, but if you can afford to own your own solar system, I think you’re much better off keeping all the electricity savings for yourself.

Solar Install Day 4

July 1. I’m in Bedford, Massachusetts for work while my favorite house project is being completed back in Ithaca. Fortunately my wife was able to take a few photos.

Our system is built with SunPower X21 panels, the most efficient on the market. I’ve read a lot of advice online that the cost of these panels aren’t necessarily worth the added cost if you have plenty of roof space (in which case you’re better off getting the best cost per watt you can). For our roof, though, these are perfect.

Solar Install Day 4 1

Solar Install Day 4 2

Perfect Painters put up their sign the first day they started work, but Renovus didn’t get around to putting their sign up until the last day of installation. I don’t mind both of us showing off some awesome solar work.

Solar Install Day 4 3

I took this photo of the finished work on July 4. Gorgeous.

Solar Install Day 4 4

The monitoring system isn’t fully installed yet, so for the moment the only way to see how much power is being produced is via the inverter’s LCD. By the end of Independence Day we had generated about 20 kWh.

Solar Install Day 4

See also:
Solar Install Day 1
Solar Install Day 2
Solar Install Day 3

Solar Install Day 2

Most of the second day of work was related to the roof hardware, though as you’ll see below the meter was installed in the basement too. One of the poor dudes had to crawl into the attic to measure the locations of each rafter, which apparently are not evenly spaced (common in older homes, I’m told). It must have been hot as hell up there judging from how drenched in sweat he was. I’ve never been in the attic space above the third floor, and I don’t have much desire to visit.

The pitch of the roof is making the work harder than expected and they’ll have to continue the work tomorrow. They may have to return Monday as well.

Solar Install 06

Solar Install 07

Solar Install 08

Solar Install 09

See also: Solar Install Day 1

Solar Install Day 1

This is really the second installation day if you count the conduit and board put in place over a month ago, but I’ll consider that a “pre-installation” since the work today kicks off what should be an uninterrupted series of days that’ll end with Renovus switching the system on.

The inverter, electrical meter and monitoring system are in. Tomorrow the panels go on the roof and hopefully everything gets hooked up.

Solar Install 04

Solar Install 02

Solar Install 05

Solar Install 03

Solar Install 01

New Conduit for Solar

On Wednesday Renovus installed new conduit leading from the roof to the basement to accomodate wiring that’ll come later. They wanted to get it in before exterior painting began, though that’s still unscheduled. Unfortunately I wasn’t able to watch the work get done as I was too busy dealing with veterinary care for one of our cats.

Solar Wiring Conduit 2

Solar Wiring Conduit 3

Solar Wiring Conduit 1

They also mounted this board to hold the inverter, monitoring equipment, and whatever other solar stuff gets installed in the basement:

Solar Wiring Conduit 4

Malibu Solar Wall Wash

I like landscape lighting but I’m too lazy to run wire and I want to minimize the electricity we buy anyway. Fortunately there are a ton of good solar options out there. Modern solar landscape lighting is brighter and warmer than the dim cold lamps you’re probably used to.

To start off, I picked up this 54 lumen Malibu LED solar wall wash from Home Depot. The reviews are excellent, and while it’s rather pricey at $40, the cost is worth it to me if the product delivers.


Wallwashers look cool and can add security if they illuminate otherwise dark corners of your home. I actually expected plastic since it seems like everything’s made out of the stuff these days, but this one was constructed out of a surprisingly hefty metal.

Testing the light

I figured a good location for my first landscape light would be the right side of the house, which is pretty dark and has no other lighting (the left side has flood lights aimed onto the driveway). The light came charged so even though it was late in the day I was able to test it out that same night.

Picking a place

Excuse the horrible cell phone photography. It’s hard to convey, but the light delivers. It’s bright, has a warmth reminiscent of incandescent lamps, and it lasted for at least the four hours of night I spent in the house painting tonight. The real test will be after it has fully discharged. The spot I placed it in is shaded and I don’t expect maximum performance (which the manufacturer claims to be 10 hours). Still, if it lasts past midnight I’ll be happy. I’ll report more on this later.

The light at night

Kicking off Solar

Our good friend Keith recently started at Renovus Energy (as of this writing the site basically doesn’t exist, though it promises a launch eventually), the premier solar installer in the Ithaca area. He gave us a great housewarming gift: coming over 10 minutes after we closed on the house last Friday to take our deposit for a 4.1 kW solar electric system with the just-announced 21.5% efficiency, 345 watt SunPower X-Series panels.

This morning we took the next step and I signed a bunch of paperwork for NYSERDA to approve the rebate Renovus will collect on our behalf. This is the first time I’ve ever signed documents on an iPad. Really forward-thinking, this company.


Also from Renovus was Joshua to perform the site evaluation. This guy was incredibly friendly and fearless on the roof. He used some shade analysis tool (it looked like one of these, but I can’t be sure) to determine that everything looks pretty good up there: decent roof pitch, minimal shading and the side of the roof facing south is away from the street, so I don’t have to care about how the array looks.

Honestly, I wouldn’t care anyway. I’m interested in maximum power output and it’s just a bonus that the back side of the house happens to be ideal. We’re also planning on symmetrical placement of panels on each side of the roof, so the layout will fulfill my OCD desire for balance.


Now we wait 6 weeks or so for NYSERDA approval. I can’t wait.