Tuesday, January 19, 2010


Hi guys,
Congratulations on your startup. Interesting monitoring site with neat data presentation.
What do you estimate the annual kwh production of this array ?? Take care

We asked for a system that would produce what we were currently using. We forwarded utility records to our installer and he told us this was the size system we would need. I went back in the blog to look at records and for the previous year we used 7984 kwh, 665/month, or 21.87 per day on average. So that is what we expect to produce over the course of the year.

We expect more light in the summer but the panels will be less efficient due to warmer temperatures. So as time goes on we hope to see increased production just at lower numbers. Our panels are 215 watt rated, so that would be the maximum number we could see on the monitoring site. For efficiency sake, if we see 188, that means that panel is converting 87% of maximum. We also expect we are using more energy with the garage addition.

The reason we went with this size system rather than the breakeven point that a smaller system offered was we wanted to be able to convert to net metering without any subsidy like payout down the road and still make all we need. With selling the renewable energy credits we will make an extra seven cents per kwh, not sure how long this will stay around.

Monday, January 18, 2010

Usage vs production

My off the cuff calculations suggest that over 10 days we averaged just over 20kwh production per day. Our most recent utility bill suggests we used 33 kwh per day. Hmm!

Thursday, January 14, 2010


sounds interesting...I have so many questions. cost to install and maintain, durability and life after install, how many days can you go without sunlight. does it store energy for a rainy day...hahahaha

Cost to install: Both my father and I found systems to be about 7K per kwh, ours is a 5.16 kwh system. It gets a little cheaper as you get larger. If this industry grows hopefully prices will come down.

Maintain: I do not know yet but do not expect to spend anything unless a panel goes bad. I recall them being tested for good 25 year life or better. With my system I have more parts, but they are smaller and if something goes bad the replacement should be cheaper (this refers to my microinverters compared to my fathers). The system I have does have a $2 per panel per year fee for the internet interface, so $48 per year to have the enphase link work.

Without sunlight? No problem as we have two meters. We still pay local utility normally, sell ours through the other meter. In the end, we should make money at this, my rough estimate is 10% return each year.

Electrical storage? We did not install a battery backup system. This would allow us to live off grid but would add five thousand to the system cost and require more maintence.

A note on system cost: NC offers 35% tax rebate on system costs, maximum is $10,500. Federal government offers 30% tax credit, no limit. So while we had to get a bank note to pay for this up front, we will only be responsible for about 35% of the system costs. With the payments for energy generated, most systems will pay for themselves in 5-10 years.

See link at topleft for my father sharing his solar experiences pittsolar.blogspot.com

Wednesday, January 13, 2010


From a friend:
Congratulations on the successful solar project. It was a good reminder to check in on your blog. That new site is cool, too.

I meant to ask a few questions earlier but I'll ask now.

1. What sort of bracket holds the panels on and is it just nailed screwed through the shingles into the roof with some patch or rubber seal around the hole?

2. In 20, 30, 50 years when the roof needs replacing, do the panels come down for that and then go back up? Does the installer do that or the roofer or Joe's nephew?

3. Does having solar panels on the southern roof affect the passive solar qualities of the building (does it make a building hotter or colder and would it depend on the type and color of roof)?

Congratulations again.

1. Our brackets are roof mounted prior to the shingles. It lifts the panels off about 6 inches. The distance should help with cooling airflow in the summer, a good thing since panels run more efficient when cooler.

2. The panels and racking material come off the roof for roof work. Likely extends a reroofing job by a week or so. Hopefully a solar company does this.

3. Solar panels should make the building cooler as they are the object that receives the heat. The shingles beneath them should be in the shade and cooler. As a side note, we went with light colored shingles to enhance the new building looking like our house and also to keep the panels cooler.


We have been producing for about a week now. We have produced around 100kwh that the in house monitor has picked up though it likely is more due to early technical difficulties. Today is expected to be nice and clear. We hope to outproduce our best day of 28.8 kwh. The enphase website does not yet have us on their reference installations list, it seems like they might have a minimum kwh total to list, today should get us to that point. We will post a link when that happens.

Edited update: See links at left. Visit the enlighten one to see near real time production and history.

Saturday, January 9, 2010

What I see

Click image for larger version. Bottom right is the enphase unit, I think it is close to "real time". Bottom row of numbers indicates what is being made now, total since power on, and number of solar modules being read.


Yesterdays generating total might be a little low as I changed outlets in the morning. So far it appears that we have generated 381W this am, all panels up and running though at low production. The inhouse monitoring unit, aka Envoy, gives data prior to the website. I think it sends data over net at regular intervals.

This is exciting.

Friday, January 8, 2010

LIVE 18kwh today

We went live on Tuesday as the sun was going down. The picture shows the final connection being made so the switches could be turned on. Since then it has been interesting to see just how much there is yet to learn. The meters are set up to be read early each am by some kind of a silent phone call. I've heard of one company called Badger Meter that does this with cell phones, I think ours are tied into the landlines here, requiring DSL internet filters. Then it took a few days to recognize that our monitoring unit was not working well as it was plugged into an outlet that was on the same breaker circuit as most of the computer gadgets are in, as these are in a surge protector the signal did not make it to the monitor. These signals get transmitted via the neutral/ground wire. We had some loud background noise on our telephone, at least for tonight it has gone away.

Our home monitoring unit relays data via broadband connection to the Enphase Enlighten web site. I've set ours up to be available for the public to see. It is not yet listed but I expect it will be in the coming days. When it is I'll try and post a link. If you follow the following link you can view reference installations of others.


Tuesday, January 5, 2010

Time to go live

We have been told that the local utility has received the interconnection agreement and that we can now go live as a generator. We expect this to happen at 3 pm today. I think this should be a simple task with flipping a few switches and installing two fuses. I will likely activate the monitoring unit before then.