A little over three years ago (my how time flies), we installed a 52kW solar project at the Westridge School for Girls, here in Pasadena. At the time, the project got a fair amount of attention (including an award from the City), was featured in a video (watch it here), and was the lead story in Enphase Energy’s Summer 2012 Newsletter.
Three years down the road, the folks at Enphase decided to circle back and check-in to see how the Westridge project had performed over the years - both in terms of saving money for the school, as well as being incorporated into the curriculum (another key goal of the project).
The article, titled — Solar on the Roof, Power in the Classroom — details how the Westridge Solar system has outperformed the modeled performance, producing 105% of the expected yield. That overproduction actually benefits the school twice: most obviously by lowering the bills that much more, but secondarily, by providing a larger than expected performance-based rebate payment.
Beyond that, however, the system has also proved to be an effective teaching tool, allowing Westridge students to analyze the copious amounts of data provided by the Enphase microinverters through the Enlighten, cloud-based data reporting service. One science class, for example, was able to discover how analyzing that data could detect the occurrence of a partial solar eclipse.
We are very proud of our partnership with Westridge and we look forward to doing another project with them in the near future.
Likewise, we are grateful for partners like Enphase Energy who are as committed to producing long term solutions as we are. That is one powerful pairing!
Recently a potential client was asking us about an oddity in their Pasadena Water and Power (PWP) electric bill. PWP has a tiered rate structure, but the most visible component of that tiering, the Distribution charge, steps up above 350 kWh of usage in any one month, but it steps down above 750! Which lead us to the question, are PWP’s electric rates regressive?
PWP’s Residential rate structure, like many utility tariffs, is a model of complexity. On your bill there are a number of obvious charges, and a few that are not so obvious. The obvious ones are on the right-hand-side of the bill and include a Customer charge, a Distribution charge, a Transmission charge, and an Energy charge. (The not-so-obvious charges include those related to public benefit programs and paying to put power lines underground.)
All of these obvious charges are tied to the customer’s usage, but only one, the Distribution charge, is tiered. At or below 350 kWh of usage per month, the customer pays just 1.5¢/kWh. Between 351 and 750 kWh of usage the Distribution charge increases dramatically all the way up to 11.65¢/kWh, nearly an eight-fold increase! Ok, the whole point of a tiered rate structure is to discourage higher use by making you pay more as your usage increases. But PWP’s rate then does something truly odd - above 750 kWh/month the rate comes down, dropping from 11.65¢/kWh to just 8.5¢/kWh! What sort of an incentive is that?
That rate design is certainly counter-intuitive, to say the least, but is it regressive? In other words, is there a point at which a large residential user ends up paying less per kWh than does someone who uses less? To find out, we modeled daily usage from 10 kWh/day all the way up to 60 kWh/day. As a reference, a typical Run on Sun client in PWP’s service area averages around 25 kWh/day. Since the Transmission and Energy charges are adjusted higher in the summer months, we broke out the overall rates seasonally as well.
Here are our results (click for larger):
The blue line is the winter rate and the orange is summer. If you use a tiny amount of energy you will pay between sixteen and seventeen cents per kWh, with rates rising sharply until you get to 25 kWh/day. Beyond that, the rate of growth flattens out markedly, but it never dips down. (That is true even if you carry the analysis all the way out to 200 kWh/day!)
Contrast this with the SCE Domestic rate - that is a truly aggressively progressive rate structure with energy charges of 14.5¢/kWh for those using within the smallest (baseline) tier of energy, going all the way up to 30.8¢/kWh for energy used in the fourth tier, which kicks in for monthly usage above approximately 900 kWh.
So no, PWP’s Residential rate is not regressive, but by flattening out the rate for usage above 25 kWh/day, it sends at best a mixed signal if the utility is trying to encourage its customers to reduce their usage.
How does this relate to solar? Well, if your usage is above 20 kWh/day you are spending at least 20¢/kWh whereas the cost of a solar power system will be less than half of that! So yes, in PWP territory - and particularly while they still have rebates in place - installing solar will still pay you big dividends.
So, you are considering a solar power system for your home or business… and why not, given the myriad of social, environmental and economic benefits! But how do you know if your roof is a good candidate? This is one of the top questions to consider carefully before investing in solar.
The size of your solar system is dependent on your usage needs and the amount you want to offset. However, it is not uncommon to find homes and businesses which are “footprint-constrained” - meaning their system size is limited by the space available.
A few things to keep in mind as you look at your roof and ponder how big is big enough… First, while there are many different solar panels they are typically the same size. Run on Sun uses LG panels which are about 65 x 40 inches and can be placed in either a portrait or landscape layout. Panel energy ratings vary, 280-305 watt panels are currently available from LG. For an average home (5 kW) that means you would need around 16-18 panels to offset the bulk of your electricity.
Another limitation is that the fire code requires three feet of clear space from all ridges. If you have an irregular shaped roof with many valleys and peaks it may make the layout very challenging. Given that the panels are rectangular and racking is mounted parallel to the roof, rectangular spaces are ideal.
Shading from trees, tall buildings, chimneys, or even parapets on flat roofs can significantly degrade the energy output from solar panels. Sometimes all that needs to be done is a generous trimming of that tree that’s gotten a little out of control over the years. Other times it means you really won’t get your money’s worth out of a solar system. But, if the shade elements are few and only during a short time each day, your roof may still be a viable candidate.
If this is the case be sure to talk to your solar contractor about inverters. We have written a great deal about the advantages of “microinverters” in handling shaded roofs, particularly those made by Enphase Energy. “String inverters” on the other hand would be a bad choice as the entire system would degrade when any single panel is shaded.
This may be the most important and frequently overlooked question to consider when researching if solar is right for you. Part of what makes solar a great investment is the 25+ year lifetime of the system. But if you have to re-roof during that time there are added costs to remove and re-install the system. If you are planning to re-roof during the lifetime of your solar array be sure you select components, such as the racking system, from companies that…A. will still be around 15-25 years later, and B. will be able to provide compatible replacement parts when pieces are lost during removal and re-installation. Avoid newer companies testing out “state-of-the-art” racking systems and cheap companies banking on the solar boom alone.
For this reason we always ask owners the age of their roof. In southern California, a roof over ten years old should get a makeover before installing solar. If you are unsure of the condition, it is a good idea to have a professional roofer take a look and give you an expert opinion. Sometimes solar contractors can offer this as part of their free assessment. (Run on Sun works with a very reliable roofer who is happy to take a look at any roof in question!) If the roof still has some life left in it but not enough to outlast the solar system you could re-roof only the area where the solar array will cover and plan to do the rest later. An added benefit is that the solar panels will actually protect your roof from the elements, helping it to last longer.
Unfortunately, you will likely be able to find someone willing to put solar on your roof even if it isn’t a good candidate. But if they aren’t discussing the above issues with you, then red flags should be flying! To ensure you get the best investment possible, do your research, take a good long look at your roof, and discuss all of your concerns with your solar contractor.
Angelinos typically struggle with cloudy “cold” days more than those accustomed to less sunny locales. So after the last few months of gloom it was no surprise to hear the National Weather Service announce that it was in fact a very abnormal year for Los Angeles.
Temperature data from around Southern California showed that the region experienced a “reverse” meteorological spring, meaning average monthly temperatures decreased instead of increasing. Average temps for downtown Los Angeles in March, April and May were 68.2 degrees, 65.8 degrees and 64.2 degrees, respectively, according to NWS. The normal averages between 1981 to 2010 were 60.6 degrees, 63.1 degrees and 65.8 degrees. Since recordkeeping began in 1877 only three documented “reverse” springs have ever occurred. But this is the first in nearly a century!
While many Angelinos may feel as if it is colder than usual, these past three months have actually been warmer and drier than normal across Southern California. The difference is we have been experiencing a cooling trend overall since the warmer than usual February. April and May actually felt more like LA’s “June gloom", typical only for June.
For those fretting over low output from your solar system…don’t worry! Your system is NOT malfunctioning. We’ve just experienced a less productive than normal spring. I’m sure the sunshine will return and your solar meter will continue to spin in the right direction before you know it. In the meantime, be thankful for any precipitation we get, and maybe even get out and enjoy the grey days that are neither too hot nor too cold!
UPDATE - Due to looming weather concerns, the Solar Impulse team decided to divert to Nagoya, Japan to await better weather. Disappointed but undaunted, pilot Andre Borschberg landed successfully in Nagoya this morning after flying for 44 hours and more than 2,000 miles, roughly one-third of the intended distance to Hawaii. Now the team will study the weather to determine the optimal time to resume their mission to fly around the world, powered only by the sun!
Solar Impulse 2 - the entirely solar-powered airplane that is attempting to fly around the world - just took off on the most audacious leg of its amazingly audacious mission: to fly non-stop from Nanjing China to Hawaii. This is a non-trivial flight in a conventional jetliner, one from which many passengers will disembark complaining of cramped quarters and a lack of sleep. But the pilot of SI2, Andre Borschberg, will need to stay awake (mostly) for six days in a cabin slightly smaller than Dr. Who’s TARDIS Police Box!
Updates from SI.TV
We have written about the Solar Impulse project before, with a mixture of awe and envy. This particular flight, however, is all awe. We are in awe of the raw human fortitude required to succeed at this attempt, and we are in awe of the courage that this pilot is displaying. Of course, he is far from alone in this undertaking, supported by a mission control center and an extensive ground support crew. But at the end of the day, he is in that cockpit alone, and the success of the flight will come down to his skill and determination.
Each day the plane greets the sunrise by a climb to altitude (flight level 280, or 28,000′), allowing the solar cells (17,000 of them) to fully recharge the plane’s batteries. During the night, the plane descends, flying on stored solar power. As morning comes around, the plane and pilot reach a critical moment - can they get to a point of energy production that will sustain them through another cycle? If they have encountered too many clouds, there will not be enough energy to sustain the mission and the pilot faces the very real possibility of ditching the plane in the middle of the Pacific Ocean! Wow!
Rest for the weary pilot comes in 20 minute breaks, ended by a gentle alarm if all is well, or a more insistent alert if something has gone awry. To maintain physical and mental health, the pilot practices both yoga and self-hypnosis, as well as a limited set of exercises that can be performed within the cabin’s confines.
You can learn more about the background of this mission, and even monitor how solar energy is powering the flight at the Solar Impulse website.
We will update this post as the flight progresses, and the video embedded here will provide live streaming of the flight so be sure to check back often during the week ahead.