|solar panels on the roof
||[Jan. 14th, 2010|02:35 pm]
I went to a brown bag lunch (or "green bag" as they called it) at work today about putting solar panels on your roof. Here is what I learned!
Two guys who had actually put solar panels on the roof were presenting. One of them has a website, agreentexas.net that has a lot of the information they presented.
- The cost is around $5-7 per "nameplate Watt", which is the panel output under ideal conditions. Of course, conditions are never ideal; gosolarcalifornia.org has a good table of different panel outputs under realistic conditions.
- Austin Energy has a $2.50/Watt rebate described here. It's capped at $15K per home (i.e. a 6kW sized array). You can search for more local incentives at dsireusa.org.
- There's a federal tax credit of 30% (probably after any rebates, although it's unclear) you can get by filing IRS Form 5695.
The general recommendation is to size your panels so that it about equals your energy usage in your lowest-energy months (presumably winter). There are some good calculators at PVWatts and PVCalc.com.
So up to a 6kW system (the Austin Energy rebate cap), it would cost us around
$2.50 per "nameplate Watt". For a 4kW system (one of the guys had this) it would be $10K.
- Rule of thumb: each extra $1K in energy production per year increases your home's value by $20K. This works out to about increase the value of your home as much as you pay after rebates, etc.
- For a 4kW system, based on the PVWatts calculator we'd expect to get 5450 kWh per year, which is $625/year under current Austin Energy rates (7.2 cents/kWH for the first 500, 11.5 cents/kWH after that). So the system would pay for itself in 16 years.
- The life of the system is at least 20-25 years (most solar panels are under warranty for at least 20 years), but you have to replace the inverter ($2-3K) every 10-15 years.
- Austin Energy provides "net billing", so they just take your consumption for the month and subtract your production and that's your base rate. This is fairly generous. Austin Energy will even pay you if you produce more than you consume, but you get a low rate for it.
- Most home insurances cover solar panels, but call and ask. Most panels are rated to withstand winds of up to 110mph, and a direct hit from a 1" hailstone at 80 mph, so they're probably not going to be damaged unless your roof is.
- No, it won't provide power during a blackout. (it shuts down when the grid is off to protect any utility workers on the power lines)
One of the guys used Gruene Energy to install his system and seemed happy with them - a few people were there with brochures, etc.
Anyway, it was a very informative session and there were probably 100 people in the audience!