Friday, October 30, 2009

Solar Spreadsheet

A lot of the solar quotes I've gotten will take your current usage to show a cost-benefit analysis. What I want to see is what happens to that benefit when my usage changes. When sizing our prospective array, I want to see how much more electricity I can use before the costs really blow up. Ideally, I want to keep grid usage in the lowest 3 tiers. So I created this spreadsheet to help with planning.

It's based in Google Docs. It's read-only but if you go to File->Make a Copy, you can save yourself an editable copy. There is a 2nd sheet in the spreadsheet called 'info' that contains instructions on how to get the data for your specific scenarios. The information is based on California's PG&E standard residential service. You can adjust the formulas, tiers, rates, etc. based on your situation. Also note that many solar households go to the time of use rate schedule instead of the standard schedule, so that will affect calculations. For simplicity, I've chosen the standard schedule. Let me know if I've mucked anything up.

Thursday, October 29, 2009

Ladders & Solar Financing

Our home is two stories and you need at least a 15' ladder to reach the lowest part of the roof. So far, of the 2 companies that have done a roof survey, both of them have showed up with a 13' adjustable ladder. When the first guy visited, I saw him pull out his little ladder and I figured it wasn't going to be high enough. After a couple minutes of watching him reposition his ladder, I offered my 17' ladder. When the other installer came, I was in the house watching him on our cameras while he tried to figure out how he was going to get up on the roof with another 13' adjustable ladder. Again, I came to the rescue and offered my ladder. These guys seriously need to think about carrying a longer ladder. If I didn't have a long enough ladder, these guys would have really pissed me off. I would have taken time off from work for nothing and would have had to reschedule.

Anyway, all these solar installers are pushing this long term lease thing - the most common is by a company called SunRun. There are a couple different options - but they both have an 18 year term. The idea is they pay the installer for the system after its installed - so they own it. Then, they lease it to you over an 18 year period. At the end of the 18 years you can sign another lease, ask them to remove the system or purchase the system at some yet to be determined amount. You can pay either a lump sum amount or monthly. Its lure is that your initial outlay, if you do the lump sum, will be less than your cash purchase price before the federal tax credit.

So for example (assuming you live in California like me), if you purchased a $22,000 system, you would receive about a $3500 state rebate. Typically, you sign the rebate over to the installer and the out-of-pocket cost would be $18,500. Then a 30% federal tax credit shaves the net cost down to about $12,500.

With SunRun, you would pay a lump sum of about $13,000 for 18 years. Of course, they throw in a few more goodies. They extend the warranty of the system from the 10 year installer warranty to cover the entire 18 years. They provide monitoring for the duration of the lease (some installers offer it for 10 years and others charge for it). If they detect something wrong, they'll send a crew over to fix the problem. They'll also come out and wash the panels once a year. Finally, they'll replace the inverter since they typically have a 10-12 year lifespan. They want you to believe this is an added $6200 worth of goods.

They say monitoring is worth $2000, but since we've already got a home automation system & server running, I can get a Brultech monitor for about $250 and monitor it myself. Maintenance is supposedly a $2700 value, but that's hard to quantify. The system is supposed to be maintenance free, and I suppose I can climb up on our roof and hose the panels down once a year (but will I do that when I'm 50 or older???). Finally, they peg the inverter replacement at about $1500. If these inverters are $1500 in 10-12 years, to me, it assumes that there have been no technological advances in that time span. In all, I would derate the maintenance costs by 50% and say the inverter will cost $500 when it needs replacing. For our situation, this gives SunRun's perks a value of $250 (monitoring) + $1350 (maintenance) + $500 (inverter) = $2100, about 1/3 of what they claim.

If we take those "perks" and add it to the net purchase cost of $12,500, we get $14,600. Compared to SunRun's $13,000 cost, the purchase will cost $1600 more, but I get years 19-30 for "free." With SunRun, after 18 years, I could either fork out some unknown amount for a new lease or to buy the system from them. Either way, it's going to cost more than a purchase. Otherwise, how would they make money?

They really push the upfront cost advantage of SunRun vs. purchasing, and that really gets people interested. Then they throw in their perks/scare tactics, to help push you over the edge, which seems to work because solar systems are not very common (and people still buy extended warranties for tv's and other household items). It seems like an OK way if you don't have the cash for a purchase, but you could probably do a home equity loan and get the tax write off for that.

Monday, October 26, 2009

More Solar Thoughts

The system I'm currently leaning toward consists of 16 Sharp 230W panels and a Sunny Boy 3kW inverter. Apparently, due to what's called stringing limitations, I cannot install a Sunny Boy 4kW inverter with 16 panels. If I chose 14, 20 or 22 panels, it would work. That changes my expansion plans.

One suggestion would be to install 16 Enphase micro-inverters instead of a central inverter. The microinverters would allow each panel to turn on individually, instead of having to wait for the array voltage to reach a certain level before a central inverter turns on. Microinverters could possibly boost output 5-10% because the panels will generate sooner and stay on later and are supposed to work better in shade and on hazy/cloudy days. Also, if one dies, the rest of the array will still produce. However, there appears to be a $2000 premium based on my system size and they are relatively new technology (but have a 15 year warranty). There is also the issue of replacement in case of failure - someone would have to hike up to the roof and possibly remove panels to get access to a failed microinverter (depending on how they do the installation). I have also been told that around 10-12 years, normal inverters will probably need replacement, so I assume around 15 years, the microinverters will need to be replaced - and there is extra labor associated with their replacement. Finally, with so many microinverters, there is an increased number of points of failure vs. a single regular inverter.

Panel brands is another topic of interest. One installer is very high on Evergreen Solar and how their panels are rated 0-10% above spec vs. other brands which can be +/- 5% or so. Sunpowers are high end, high efficiency, but somewhat restrictive with their installation. Perhaps this is why none of the 5 quotes I received used Sunpower. Sanyos are also high efficiency and high priced, but are manufactured/assembled all over the place. Obviously, each dealer will tout the panels whose manufacturer they have deals with or which provides them the largest profit margin.

For the consumer, it ultimately comes down to cost, wattage and size (room for future expansion) - at least it does for me. When you start to use the more exotic panels, it's hard to justify the longer breakeven period. I chose the 16 230W panels instead of 20 175W panels due to density - I want to have room on the roof for future expansion. The 20 175s would nearly occupy the entire back roof. I could get 16 Sanyo 215W panels for a $2000 premium (and 240W less output) vs the Sharp 230W. The Sanyo's are about 8" narrower so I could squeeze 2 extra columns - or 4 more panels - in the space of the 230W Sharps. Overall, I could squeeze up to 27 Sanyo's vs 20 Sharps - 5.8kW vs. 4.6kW output - a pretty large difference.

I am leaning toward the 3kW inverter at this point. In the future, if we need more capacity, I could then go with microinverters for the additional 4-6 panels that there's room for. With today's panels, I have room to go from 3.7kW to 4.6kW, but in 5 years, panel density will be better - so I should be able to get more power out of the remaining roof space.

Wednesday, October 21, 2009

Planning to go Solar

I just had a site evaluation with an installer we're considering. He checked a few things out - the roof - and it's in great shape and the electrical panel - which can easily accommodate the extra amperage. Then he ducked into the attic to check the structure and take a few pictures. While on the roof, he took measurements and made note of obstructions like vents. Some short vents can be cut even shorter and panels can be installed over them. The lowest efficiency we'll have would be about 98% due to our back neighbor's Italian Cypress, which will cause some shading in the early morning. I may ask the neighbor if we can cut it down a little. Our back roof has a SE facing, while not optimal, is still very good in terms of sun exposure. Based on this, we should qualify for 92% of the California solar rebate. Next step is for the installer to send a couple plans with different panels and outputs. We're looking at a 3.5-4 kW system which will reduce our yearly electricity bill by about 72%. I also need to think about future needs and roof space for expansion like an EV car or 40" LCD touchpanels for automation ;) The installer has a bit of a backlog, combined with the winter weather and holidays, the soonest they could start would be January. Power on might not happen until March due to inspections from the city & utility. I have 3 other installers to look at, but I'm leaning toward this one as they did a great job on my co-worker's array several months ago and have had an answer for every one of my questions (I ask tough questions! ;)

Tuesday, October 20, 2009

xPLSerial Released

It's been a while since I released an app. xPLSerial gloms together a generic serial port interface, xPL and a scripting engine. Read more about it and download it here.

Monday, October 19, 2009


I've decided I needed to code up something to deal with serial port devices I may want to interface with. I've put serial device handling into my starCOMUltra hosted script as well as in my sCU-xPL bridge (xPL sCU), but while I'm debugging stuff, I don't want to keep reloading those apps as much of the HA system relies on it functioning correctly. There doesn't appear to be an xPL app that allows generic serial port interfacing, so I figured this would be a good (and easy) app to write. A majority of the code comes out of xPL sCU since it already does serial & xPL as part of its features. Because of this, I've already got a prototype running. It relies on an internal scripting engine to set up the serial port, send data to it and parse data from it. You can then issue xPL messages as necessary. Right now, I'm working on interfacing to an Ocelot I just acquired.

Thursday, October 15, 2009

Cheap Low Tech Home Security

Recently, I've gotten tired of coming home from work to find random flyers attached to my front door. Aside from the hassle of having to toss the papers in the recycle bin, the flyers are an obvious hint to thieves that there's probably nobody home. I stuck a "No Solicitors" sign on the front door a couple months ago and have had good luck so far. Our security cameras have captured a number of these spammers walking up the driveway, but once they get close to the porch and see the sign, they turn right around leaving nothing. No flyers and no door-to-door solicitors makes the WAF high and makes this a high bang for the buck "project."

Monday, October 12, 2009

Updated Cellphone to Windows Mobile 6.5

I finally got around to updating my HTC Touch Pro from WM 6.1 to 6.5 using this build. I've been playing around with it this weekend reloading and re-customizing. It seems a little snappier than 6.1. I like it.

Sunday, October 11, 2009

Homemade Avermedia Quad Viewer

I've been working on more web pages for our user interface (much cheaper than constantly buying hardware!) I thought I'd share some code on a simple quad viewer I coded up. I previously had single camera views on our floorplan GUI so this was really easy to add. Since our floorplan is web based, it will work on all platforms, which is great since the Avermedia software only works on Windows.

The Avermedia software has special URLs where you can view compact images of each camera. With a little JavaScript, you can have them refreshed at periodic intervals. First off, you start off with an HTML shell that defines the cameras - let's call it cam.html:

<SCRIPT SRC="cam.js" language="JavaScript"></SCRIPT>
<body onLoad="refreshCam();">
<img src=images/blank.png id=livecam0 style="position: absolute; left: 263px; top: 15px;">
<img src=images/blank.png id=livecam1 style="position: absolute; left: 620px; top: 15px;">
<img src=images/blank.png id=livecam2 style="position: absolute; left: 263px; top: 255px;">
<img src=images/blank.png id=livecam3 style="position: absolute; left: 620px; top: 255px;">

A few key things are the reference to the JavaScript file, cam.js and the call to refreshCam() when the HTML loads. Each img tag defines a camera view for each of the 4 cameras (you would put more if you have an NV5000 with more cameras).

The JavaScript file, cam.js, is below:

var camNum=0;
function refreshCam() {
if (camNum==0) {
} else if (camNum==1) {
} else if (camNum==2) {
} else {
refreshCamId=setTimeout("refreshCam()", t*1000);

Every time refreshCam is run, one of the camera views is refreshed depending on the camNum variable. The URL given is the special Avermedia URL - and each image in the HTML is associated with a camera's URL. Every iteration, camNum is incremented and the sum has a modulo 4 operation done on it - resulting in a value that changes from 0 to 3. The setTimeout function causes refreshCam() to be run every 0.2*1000 milliseconds. That's pretty much it. You can use any camera server you want - just substitute the URLs in the JavaScript.

Monday, October 5, 2009

Snagged Free Win7 Ultimate

I went to Microsoft's The New Efficiency Event and got a free copy of Windows 7 Ultimate. I don't have a machine to install it on though. I'd like to eventually port my apps to Win 7.

Other than that, I've just been re-theming and updating my ASP pages and doing some reading on PHP & MySQL.