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Wednesday, February 06, 2008

Greener Q & A

Thanks for all the comments on "Greener". I usually reply by email, but given this is a new area for many (including me), I'll answer in the blog. The information in this post comes from personal experience or from information supplied by the solar companies. (And for those who are not familiar with the term, PG&E is our power company and stands for Pacific Gas & Electric.)

A solar electric system generates DC electricity which is converted to 120V AC by the Fronius inverter. The AC is then fed into a bi-directional electric meter and the home's circuit breaker panel. The electricity is either used directly in the home, or sent to the grid, or some to each. If excess electricity goes to the grid, our meter will spin backwards. PG&E does not pay customers money if they contribute more electricity than they use. The best we can hope for is zero charges for electricity usage on our bill. We do not have a battery back up system, so no energy is stored at the house.

Jeni wrote,
Too bad they can't come and install them just before dawn, eh?

I wish there was some incentive to get apartment buildings to use solar energy... if just for the ground lighting and swimming pool, etc.

Tomorrow the city inspector will--well, inspect--and sign off on the install. After that, PG&E needs to come out, bless the system, and install the bi-directional meter. So we're not supposed to be generating any electricity right now. We've been warned that PG&E can take up to 2 months to do their thing. Why doesn't that surprise me?

With regards to incentives, California has a solar program. The state incentives are on a sliding scale--as the money in each tier is claimed, the incentives are reduced. So, it's better to install sooner rather than later. I'm sure the sales guys love the fact that the state is providing them with a sales tactic... it motivated us to take action. True to form, the calculations for the State rebates are so complicated, they're best left to the professionals.

The Federal Energy Policy Act of 2005 provides for a federal tax credit of 30% of total system cost of a solar system, up to a maximum of $2000, per system. The credit is available to homeowners for solar systems placed in service from January 1, 2006 through December 31, 2008.

Suzie wrote,
Wow, that's awesome. We want to do the same thing, we just have to get the rest of our co-owners to agree! Did you get any help from PG&E?

We only contacted PG&E to get usage history--the information was not available through the web site when we tried to download it. For the solar system, we worked directly with the solar companies.

The process to get a quote was straightforward--provide your monthly energy usage for the past 6-12 months and have an idea of how much you want to offset. For example, do you want to cut your electricity bill in half or wipe it out completely? A rule of thumb we heard was if your electricity bill averages $100 or more per month then solar begins to makes sense. Do you want panels or PV cells integrated in roof tiles ($$$)? What kind of roof will the array be installed on? etc., etc.. Soon we had quotes that included the rebates and incentives in the net price.

The quotes showed the cost of the system, how much money we would save off our electricity bill, and how long it will take for the system to pay for itself. (Don't ask, it's a looooong time.) For our quote, the calculations assumed 5.2 hours of equivalent full noontime sun based on 30-year annual average for our area and shading & orientation factors.

The quotes assumed that we will change our rate plan with the power company. Many residential customers are on a Residential Tiered rate, meaning that the more electricity you use, the more expensive it is. The quotes assumed that we would switch to PG&E's Time Of Use (TOU) rates which value electricity differently depending on time of day and season. During the day the rates are high when the electricity demands are high and our panels will be generating as much as their photo voltaic cells can muster. Whatever energy we don't use will be sold back to PG&E at the higher rate. In the evening when our panels are silent, the rates are lowest. Made sense.

Next came in-home sales calls to review the quotes--the meetings were typically over an hour because we had lots of questions. One thing I wondered about was the impact on the resale value of the home. The Appraisal Institute published a study [PDF] in 1998 & 1999 that established that a home's resale value increases $20 for every $1 saved in operating costs. If this study is accurate, 87% of our system's net cost would be added to the resale value of our home--market willing of course.

One reason why we went with Solar City is because the system includes remote monitoring at no extra charge. If our system generates less power than expected, they'll contact us and help remedy the situation. The most common cause of an inefficient system is dirt on the panels which we would take care of with a garden hose. Also, I'll be able to access my system's monitoring on their web site--geeky!

Seltsame wrote,
That is really cool. So how does it work out? What percentage of your electricity needs can you get out of the panel?

How much energy you get out of the array depends on how big the array is. A 16 module array would have reduced our bill by 83%. The 20 module array that we had installed is rated at 4kW DC and will offset our bill by 95%.

All of this assumes that we use the same amount of electricity moving forward. But now I'm looking at the gas water heater that needs to be replaced and thinking about an electric tankless water heater. AC won't be as expensive to run in the summer and what if we buy a plug-in car in the future? We're going to have a different perspective when it comes to electricity usage in the future.

Freecia wrote,
Did you get on the roof or hand your camera to someone already on the roof? Because I think this is the first "I got on the roof for this blog" shot I've seen.

Spinnity wrote,
Yeah, I'm with Freecia -- if you went on the roof for your blog, you deserve some sort of blogmedal!

We were invited to climb the installers' ladder and take pictures on the roof, but I sure the heck wasn't going up there! R went as far as the top of the ladder and handed our camera to the project lead. I wish I could say I was up there, but I wasn't.

For all those that made it to the end of this post, here's another interesting tidbit. I found Solar City through Facebook. I posted a question on the Silicon Valley network (or was it the UC Berkeley network?) and a woman who works for Tesla Motors said they're recommending Solar City to their customers. It turns out that Solar City was launched with $10M in financing led by Chairman Elon Musk, the founder of PayPal and an investor in the electric-car company Tesla Motors. Now there's an electric car I wouldn't mind driving.

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  • I really like your "quote" feature. It makes them stand out and looks cool!

    By Anonymous jessica, at 2/06/2008 7:15 PM  

  • I might be mistaken, but I think the TOU rates are tiered as well. Good overview! FWIW, my friend who works in the solar industry says the roof tiles really aren't there yet - current solar technology doesn't work well when it is hot (ironic isn't it) so therefore panels installed with some spacing above the roof are performing much better than PV roof tiles. We also have a 4kWh system - probably too much for our current use but with room to grow for that electric car!

    We went with a company that absorbed the cost covered by the rebates, so we ended up affording a bigger system than we otherwise could have (the quality of their contracters is another story...). Also, our PG&E approval happened within about 2 weeks (the meter had to be replaced with a digital, so if you have one that you can see turn backwards, get your video now; ours just has a negative sign when it's going backward- much less dramatic).

    By Blogger Kim, at 2/07/2008 9:36 AM  

  • Also, we got (included with it?) a wireless receiver that records the power generation directly from the inverter - it sits on my DH's desk and he checks it at the end of each day.

    Apparently the digital electric meter can be soft updated, and has monitoring capabilities, although ours does not have them turned on or accessible to us.

    By Blogger Kim, at 2/07/2008 9:38 AM  

  • Thanks for commenting Kim.
    I wanted to point out what I saw as the biggest difference between a strictly tiered rate and the TOU rates, but you are correct that the TOU rates are tiered as well.

    Hopefully our PG&E visit will happen quickly, but the request for the PG&E inspection can't be made until the city signs off. I hope the recent storms around the Bay Area don't impact how soon they can come out--no idea if the people who inspect and install the new meter are the same folks who are busy repairing storm damage.

    I believe our new meter will have a digital read out as well. We'll see after it's installed.

    We don't have details about the monitoring yet. Unless there's a wireless transmitter in the inverter, there's still more to do to get our system to send data to Solar City. We'll see!

    By Blogger Bogie, at 2/07/2008 11:14 AM  

  • This is fantastic -- and thanks for the extra info.!

    By Blogger Octopus Knits, at 2/15/2008 7:30 AM  

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