Lowest Achievable CPW Installed @10KW (rooftop)?

[sunnyguy]

Anyone have any advice on when to consider putting panels on a NE facing roof? PVWatts says it produces 20% less energy so 20% longer payback period.

[J.P.M.]

Anyone have any advice on when to consider putting panels on a NE facing roof? PVWatts says it produces 20% less energy so 20% longer payback period.

1.) When it's the only option.

2.) When it's a better option than all the others.

20% less output than south facing sounds about right. The economics will probably be in about the same neighborhood depending on a lot of things like usage patterns and POCO tariffs and particulars.

One way to get the 20% back: Lower consumption by 20%. It's cheaper than solar.

[sunnyguy]

1.) When it's the only option.

2.) When it's a better option than all the others.

20% less output than south facing sounds about right. The economics will probably be in about the same neighborhood depending on a lot of things like usage patterns and POCO tariffs and particulars.

One way to get the 20% back: Lower consumption by 20%. It's cheaper than solar.

It was actually 20% less than SE/SW since those are the options. As you can see, there is a lovely open NE section of roof for panels.

Here is my roof. Street side is at the bottom (SW) side.

http://i.imgur.com/slFiAdc.png

Here I was able to fit 36 panels:

http://i.imgur.com/6AR3y3f.png

Anyone have comments about shading due to roof geometry ? Roof pitch is 18.4deg.

[sunnyguy]

Here's another view with 54 panels possible locations.

http://i.imgur.com/mCeUo0U.png

Right just just figuring out placement options. Is it possible to place panels/racking at 45deg to rafter orientation? Comments welcome.

[sunnyguy]

Is the best thing to measure the solar radiation at all the possible locations at different times of the day using a meter? Any affordable/reliable ones?

[sunnyguy]

Anyone have any data on average % of total production that happens after 12pm?

Based on some back of the envelope calculations, if the system can produce 60% of its power after 12pm then 1W of solar generates approx $0.29 worth of electricity in a year based on my power bill.

So a 5 year payback is doable if cost per watt installed is $2.20 before tax credits.

That means the system should favor a more western orientation.

[J.P.M.]

Check out something called PVWatts on the net. Data for Edmonton, AL is in that database.

It's an estimating program from the U.S. NREL and may be of help in answering your questions. Spend 20 min. reading the help/info screens before making a few runs. With a bit of practice, and reference to the help screens, you'll probably get a quick education. Then, download the hourly output option to excel and after some spreadsheet finagling you'll get a decent estimate as to how much production to expect for your location.

[sunnyguy]

Check out something called PVWatts on the net. Data for Edmonton, AL is in that database.

It's an estimating program from the U.S. NREL and may be of help in answering your questions. Spend 20 min. reading the help/info screens before making a few runs. With a bit of practice, and reference to the help screens, you'll probably get a quick education. Then, download the hourly output option to excel and after some spreadsheet finagling you'll get a decent estimate as to how much production to expect for your location.

Thanks for the pointer. I've used pvwatts but never noticed the hourly download data.

According to that, a SE oriented system will generate 48.3% of its energy after 12pm and a SW oriented system will generate 63.8% of its energy after 12pm.

[sunnyguy]

Anyone have any advice on POCO rate plans for APS?

If you're on a demand charge plan once the sun goes down and before 7pm you're going to get hit with probably a similar demand charge as if you didn't have solar.

If you're not on a demand charge plan you get hit with a monthly solar fee of $5 (but they are raising it to $20).

If someone can post an example APS bill that would be great.