Our system consists of eighteen 175 Watt BP Integra Panels strung in three groups of six. Click for a pdf detailing the panels. We went with BP panels for a number of reasons – a) cost, b)looks, c) they are a Maryland company and we want to support local businesses – even if they are huge corporations, d) they are made by BP, an oil company. We want to show these kinds of companies that solar is a good investment, e) they are made less than 50 miles from our home, so the carbon involved in shipping them wasn’t too high.
The system is 3.15 kW and faces west – southwest (240 degrees). This is not an ideal direction -- due south is best for a fixed array.
Our inverter is a Xantrex GT 3.3.
It was installed by Standard Solar of Gaithersburg, MD. We were very happy with their work. It took them two and a half days to complete the installation. It was completed on February 2, 2008.
According to my calculations on PV Watts, our system should generate between 3209 -3361 kWh per year. That will be about one third of our annual electricity usage. Check out our inverter output to see how we’re doing today.
We are enrolled in BGE’s net-metering program. We use a GE Watthour I 70S meter, which is the standard meter for our area.
The money
We received a $3000.00 grant from the State of Maryland about a month after installation, and a $5000.00 property tax credit from Howard County, Maryland for the next fiscal year. We subtracted $2000.00 from our Federal Tax bill in the form of a credit. That’s not a deduction, where you subtract from the income that the government taxes, but a credit where you actually subtract from the amount you owe (or, if you usually get a refund, think of it as an addition to your usual refund). Our incentives added up to $10,000.00 off the price of our system.
Those considering buying a system should note that the $2,000 cap on the Federal tax credit was removed for systems installed after 1/1/2009. Current installations will receive a credit for 30% of the cost of the system. Additionally, the Maryland grants (http://www.energy.state.md.us/incentives/residential/solargrants/index.asp) were also increased since our installation. Grants are currently being awarded up to $10,000, but stay tuned, because the process is under review again.
We also sold our REC’s in the emerging Maryland solar REC market. We only generated 2 REC’s in 2008, but we sold them for $315 each. If the trend of selling RECs for about 70% of the current ACP holds, then we will make almost $9000 from the sale of our REC’s over the next 16 years. So, all in all, our system should end up costing us about $7,000.00 out of pocket. For us, this works out to about 12 cents a kilowatt hour for 20 years. That’s just a penny per kilowatt higher than we currently pay, and I do expect rates to go up, so we will probably break even before 20 years. The panels should last longer than 20 years but I’m just not comfortable counting on much of anything for longer than 20 years. The industry standard estimate seems to be 25 years. In any case, if by some miracle, electricity rates don’t change for the next few decades, it will take us 20 years to make back our investment. If rates go up by just 2% a year – it will take us about 18 years.
The payback
Over 20 years, we will have prevented 82 tons of CO2 from entering the atmosphere. I would need to plant 12 trees a year, each year, for 20 years to have the same effect. It doesn’t seem like that much at first, until you think about the amount of space a tree actually takes up when it’s fully grown. Now think of 240 of them. I don’t have that much space on my lawn. Plus, there’s evidence (pdf) to show that planting trees in a temperate zone is not going to combat global warming. But I did have the room for 18 panels on my roof.