Submitted By: Steve Richard (swrichard@comcast.net)
Updated: August 2008
UPDATE: We have now been running our solar system for 17 months. Over that period our electricity bill has averaged $46/month, compared to $200-250 before (reduced 80%), so we have saved over $3,000 so far. Our lowest bill is in the middle of the summer (negative) and the highest is in the middle of the winter, when there is less sun light. We have also been improving our conservation efforts so our bill has only averaged $16.70 over the past 5 months. In July, our bill was actually negative since we produced more than we used. We cleaned our panels a couple weeks ago for the first time and the energy production jumped dramatically. This is especially important when it hasn't rained in a while. We're going to clean them more often from now on. I'm planning to re-investigate the different rate schedules, because I have a friend who just told me that his bill for the first year was ZERO (same size house and solar system), but he is on the "time of use" rate schedule (E6) where you sell energy in the afternoon (12-5) for three times the rate you pay for it during the rest of the day.
Challenge
My goal has been to move our home towards a guilt free home that minimizes greenhouse gases that contribute to global warming. I learned that 70% of electricity in California is generated by burning natural gas. Natural gas burns much cleaner than coal, dramatically cutting visible air pollution, but unfortunately still produces a similar amount of greenhouse gases (roughly 2/3rds as much). Conservation is certainly the least expensive way to save energy and emissions, but it was hard to imagine cutting our energy use by more than 30-40%. Realizing that made me interested in looking at solar as a way to provide our core electricity needs without producing any emissions.
Last year an article in Sunset Magazine caught my eye and highlighted a solar vendor called SunPower in San Jose. I went to their web site without any knowledge whatsoever about solar systems and filled out a form to be referred to a local dealer. I received a call a few days later and quickly realized that there were many things to figure out such as:
- whether we were a good candidate for solar (based on our roof layout, orientation and angle, and level of shade),
- what a solar system really costs after all the rebates and whether it would be a good investment
- what size system (# of panels) would make the most sense for us
- whether a solar system would look OK on the front side of our roof
- which dealer and solar panel manufacturer would meet our needs the best There are many options to consider and it seemed a little overwhelming trying to sort through it all.
One of the dealers we talked to (Sun Light & Power) could quickly evaluate our roof situation over the phone using Google Earth. By zooming in they could see the exact direction our roof faces, slope of the roof, trees, and even what type of shingles we have. Very cool!
Solution Details
After getting detailed proposals from two dealers we decided to purchase a solution from Sun Light & Power in Berkeley that included 18 SunPower SPR-215 panels and an SPR-3300x inverter. SunPower panels are the most efficient on the market (captures a little more energy in the same amount of space) and also designed to be attractive as possible with a unique “all black” finish (vs. visible lines). Sun Light & Power has been in business since 1976 and seemed very knowledgeable, thorough, and professional.
We really debated how many panels to buy. The greater the number of panels the higher the percentage of your total electricity you can handle, but also the greater the cost. Solar dealers give you a detailed analysis for each configuration they propose. We ended up choosing 18 panels because it fit nicely on our roof (two rows of 9), because it cost an amount that we were comfortable spending, and because it would provide at least half of our total electricity needs. Also, as we looked at adding more panels (beyond 18) we would be forced to begin using less ideal locations on the roof, due to shade or other factors. I was drawn to the idea of adding more capacity later, like adding more memory to a computer, but it’s not as simple with solar panels because everything is setup to work in a specific configuration.
The full cost of a solar system for electricity seemed expensive, but was somewhat less intimidating after factoring in the sizable rebate from the State of California (about $8K) and also the maximum $2,000 tax deduction on our federal tax return. These deductions brought our net cost down to the low 20’s vs. the low 30’s. There are starting to be solar financing options available, but I didn’t investigate that.
It’s been interesting to learn how a solar system works. Solar panels are made up of solar cells, which are semiconductor devices that directly convert sunlight into electricity. SunPower’s cells are supposed to be the most efficient on the market, converting about 20% of the Sun’s energy into electricity. That electricity is run through an electrical conduit to an “inverter” on the side of our house. The inverter converts electricity from DC to AC, which is what our house uses. The inverter connects to our main electrical panel providing a second energy source, besides the line coming from PG&E. I didn’t really think about it, but without batteries, energy is created and used simultaneously. If we generate a surplus, the excess current will flow to one of our neighbors!
Having solar panels installed was a multi-step process involving the following steps and taking about six months in total:
1) Determining our goals
2) Learning from solar dealers what’s possible, what the tradeoffs are, and what various solutions cost
3) Choosing a solar dealer and a specific proposal that they’ve made - sign a contract and make a deposit
4) The “engineering guys” came out from the dealer to make more detailed measurements to prep for install
5) Actual installation – panel installation and associated electrical work. This took a couple of full days.
6) Inspection by the City of Lafayette
7) Final visit by PG&E to upgrade our meter and bless everything.
On March 21st, 2007 our whole family went to the side of our house and took pictures while we turned on our solar system for the first time. At that moment we were using about 700 watts of electricity and we watched as the digital meter began to go down, down, down, passing zero and starting to go back up again. At first we thought something was wrong, but it was starting to show the excess energy that we were putting back into the grid – reaching about 1300 watts. So, our system was producing around 2000 watts and we were only using 700 of it at that moment!
Now that the system is installed there is no maintenance to speak of and nothing to manage. It all works automatically. Our billing has changed and we will now get billed only once a year for electrical – to pay for the net amount that we used.
Benefits & Payback
Our household has been averaging about 1100 Kilowatt hours per month in electrical usage. Assuming that we are providing about 55% of that with our solar panels we are expecting the following benefits and payback:
Environmental Benefit:
Without knowing the specifics I feel our family has taken a giant stride towards a guilt-free house that doesn’t produce much emissions. Based on government estimates that 1.321 pounds of CO2 is produced for every Kwh of electricity generated from burning natural gas, our own home has been responsible for producing about 12,000 pounds of CO2 per year (just for electricity). If we produce 55% of our electricity with our solar panels than we are preventing the release of about 6,700 pounds of CO2 each year for the next 30 years.
Financial Benefit:
One of the things I didn’t fully realize is that our electricity is charged on a tiered basis. The more you use the more expensive it gets. Looking at our bill, the cost per Kwh jumps dramatically when we exceed 200% of our baseline. So, as an example, if we provided 50% of our own energy on our Jan-Feb 2007 bill, our monthly cost would have been $85 versus $271.42. In other words, reducing electrical use by 50% cut our electric bill by 70%.
Sun Light & Power estimates that our system will save us close to $2,000 per year and fully pay for itself in about a dozen years. After that the electricity from our roof is free!
Solar dealers also like to remind you that solar panels should increase the value of your home by the amount that the system costs, so we’d get back our investment even if we sold our home.
Informational Links
SunPower - Manufacturer of solar cells, panels, inverters (headquarters in San Jose)
Sun Light & Power - Providing complete renewable energy solutions in commercial and residential applications since 1976 (based in Berkeley)
