Solar Panels for homes

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Permalink Reply by Kristen Bareuther on January 5, 2008 at 8:30pm

Draya, you speak so well... so young! One of our companies installed solar panels on the roof of the building which will power our entire warehouse. The State of CT paid for the purchase and installation of the panels. I have no idea who they contracted, but can find out. Its not really for homes though... if you think its of interest, let me know and I'll look into it.

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Permalink Reply by Doug Coleman on January 21, 2008 at 2:46pm

I've had solar installed on my house. While I'm still happy I did it, the experience hasn't been entirely positive. My initial calculations indicated I would have payback in about 10-12 years (with the CA state credit). But, I'm only producing 30-50% of the kWh I thought I would, so payback is going to be about 24 years. Oh well...

On the plus side, its a nice feel good thing to do. And maybe some day I can bank credits and sell them. The investment slowly depreciates so if I sell the house the panels still provide value.

The outfit I used in SoCal at the time was New Vision Technologies, but they have since been bought by SunEdison.

Doug

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Permalink Reply by SustainGigs on January 23, 2008 at 6:51am

Hi Doug,

Do you know why your initial payback came in so much lower than what you are getting? Has it been less sunny than expected? I've also heard some installers get aggressive in their estimates, is this what happened? Any thoughts from a perspective solar user. Also, did you look into a power purchase type arrangement?

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Permalink Reply by Doug Coleman on January 31, 2008 at 7:36pm

I think it was the installer getting aggressive to make the sale. The worst part is I requested and got the spreadsheet that they provided and did the analysis myself as well. At the time, I recall thinking that it seemed right. However, I've since lost that spreadsheet so I can't go back and understand what I missed.

Just make sure you do the calculations yourself and compare with what they're saying. For example, they might use metropolitan area solar intensity averages when you in fact are in a foggier area. That must be factored in.

I did not look at power purchase arrangement, so I couldn't comment on that.

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Permalink Reply by Andrew on January 22, 2008 at 2:34am

Hi Draya, In Australia it is very popular - here are a couple of links to research it.
Essentially it comes down to what angle your roof is at relative to the sun (http://www.greenhouse.gov.au/yourhome/technical/fs47.htm)
and the efficiency of the solar cells

After I read a little more about it, it appears that if you plan on using the electricity to heat your water, then installing heat pumps, you can increase energy efficiency by 3x, which is very very helpful to reduce energy usage (http://www.enviro-friendly.com/quantum-heat-pump-water-heater.shtml)

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Permalink Reply by Brad Juhasz on February 18, 2008 at 7:22am

Unfortunately, I don't have many answers for you, but I just came across this website from a self-proclaimed "mechanical engineer, DIYer and avid environmentalist" and he has information all sorts of topics including solar heating.

According to his site, he is a nationally syndicated columnist as well.

Check him out at www.dulley.com

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Permalink Reply by Gregg on July 7, 2008 at 1:05pm

It's awfully long, but here goes . . .

I assume that we are talking photovoltaic (electricity generating) solar panels. Enter "photovoltaic" or "PV" into any search engine and you will be confronted with thousands of websites with information and sales of photovoltaic panels.

The way most people install solar panels - bolting them to the roof or mounting them on a post in the yard - it turns out the same for new construction or retrofit.

============================================================

Do a quick exercise to understand the practicality of generating your own electricity.

#1 Determine how much power you use. Most sizing guides tell you to read the power tag of every electrical item in your house. It is s-o-o much easier (and more accurate) to dig out your electric bills and see how much you have used each month for a year. You are looking for how many kWh (kilowatt hours) you used.

#2 Find the highest usage month - probably July or August if you have air conditioning or January if you have electric heat.

#3 Find your 'average' use by adding up all 12 months usage and dividing by 12.

#4 Armed with these numbers you can determine how big a system you need. To be entirely electricity self-sufficient, you will need to use the highest usage month to size your system. If you want to drive you electric bill to near zero and your utility company will pay you for your electricity, use the average usage number.

#5 Divide the usage number by 30 to get your daily usage.

#6 Armed with monthly and daily usage, you can go to sites like this one
http://www.southwestpv.com/home_solutions/medium_home_solutions.asp
to see how much a system will cost.

My house as an example:

Peak month 1634 kWh
Average month 950 kWh

Using the website above, we find the smallest system that meets my average usage is GT10000. It produces 1063.7 kWh/month in zone 4.5 where I live. It could meet my 'average' usage for an up front investment of $62,000. To meet my peak needs, I would expect to scale it up to about $62,000 X (1634/1063.7) = $95,000. (As a 'sanity check' for my estimate, a GT10000 plas a GT7500 would cost $62000 + $44000 = $106000. My $95,000 number isn't too bad.)

These are kits. Installation is not included.
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Most folks will say, "but you have to reduce your consumption." (I'm old and diabetic and I really cannot live without air conditioning here in coastal Virginia) However, for this example, let's say that I do reduce my usage by 50% so that I could use a GT 5000 to meet my average usage. Then my up front cost would be reduced to $31,189 (plus installation).

If you want to take this approach, that is an experiment you can do starting today. Commit to reducing consumption to 50%. Learn to read you electric meter and track it day by day. See if you can do it.

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The best solar site I know is
http://www.builditsolar.com/
Check out the 'half' plan. It is a good way to get maximum return on the $ you spend. Gary Reysa who runs the site has done most or all of the half plan projects.

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Permalink Reply by Mark L. Miller on March 30, 2009 at 1:15pm

There is a lot of activity in this area these days. The actual cost per installed kilowatt is still 4-5 times conventional generating alternatives. Here's an outfit that just got !/2 $billion to expand their manufatering plant, so they must be doing something good (or something that's in vogue) http://www.solyndra.com/ . Solar sill never be able to replace baseload generating needs, but it's a vital piece of our energy PORTFOLIO.

BTW, For what other consumer product (like a TV, car, sofa, etc) do we even ASK the question, "What's the payback period?" In the longer term, solar PAYS for itself...then keeps on paying for FREE!

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Permalink Reply by rripken on May 12, 2009 at 11:06am

I'm all for conservation, installing solar and solar thermal but stating that "solar PAYS for itself and then keeps on paying for FREE!" Is misleading. There is something called the time value of money. By investing in solar you are losing the opportunity to have invested that money somewhere else. Those same dollars could have instead been in an interest bearing account making 5% interest. Such an account would pay for itself in 14-15 years and, by your reasoning, keep on paying for free - without having to look at the panels or risk that the inverter will break or your roof start leaking or any of a number of other problems. I agree there are lots of upsides to PV but if you want the system to also make financial sense then you need to be able to somehow weigh the price of the system versus what you get for your money. The payback period does a pretty good job summarizing whether the investment is a good idea or not.
People don't frequently ask themselves what the payback period is b/c most people are in debt and not making long term investments. They most frequently are trying to figure out how long in the future they will be paying for the TV, car or sofa, house they want today.

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