Energy costs are on the rise, and each year my electric bill seems to grow at an annoying pace. When my last bill hit over $400, I realized that it's time to seriously consider PV (photo-voltaic) solar panels for my roof. Generating power from solar panels has become more attractive over the years for many reasons. First, the price of solar systems has dropped in recent years and the rebates (both state and federal) can substantially reduce the total cost of the system. Currently, there is a 30% federal tax credit and local power companies such as Southern California Edison (SCE) offer a meager, but still significant rebate of around $0.20 per Watt. There are different types of solar systems to consider and it is important to do your homework before committing to any one. I contacted a total of 6 solar companies and eventually met with 4 of the contractors to better understand the whole process. In the end, I received written quotes from each of them.
Choosing the Right Solar Contractor
Having done research on PV solar and having an electrical engineering background, I had a good amount of knowledge under my belt with a particular bias on what I wanted in my system. There are many factors to consider when choosing your configuration and the solar contractors will help educate you on the benefits of solar energy, thereby making it easier to sell. After all, the cost can be substantial even with the rebates, with a typical payback period of about 7 or 8 years, depending on the amount of energy you consume each month and how well your system produces power (i.e. shading issues, panel mounting angle, etc.). So being happy with your long-term investment and decision is very important. Bear in mind that many solar contractors have particular systems that they may want to push, so it's good to understand the pros and cons of each system up front. This certainly helped me make a sound decision.
LA Solar Group
One of the companies that I particularly liked during my search for an installer was LA Solar Group, mainly because of the response I received from them regarding my particular needs and their high rating on Yelp. The person I met with was Sales Director James McCann, who provided a great deal of information and was willing to work with me to meet my solar requirements. The company offered a good price (about $4 per Watt) on the solar system, which included 26 - 290W LG solar panels along with the more costly Enphase M250 microinverters. In addition, a 200A power panel upgrade was included in the price. Once the contract was signed with a $1000 deposit, I began to work with LA Solar Group's engineer/consultant, Ara Petrosyan. Ara is very knowledgeable and has been great at answering my many questions about the permitting/installation process. My questions were largely related to panel placement on the roof, microinverter selection, solar panel selection, sub-branch wiring, branch circuits, wire gauge for branches, etc., not to mention the permitting/approval process.
So what choices are there when it comes to configuring a solar system and how does this affect performance? The first decision was to choose what type of inverter (string or micro) to convert the solar panel DC power to utility-friendly AC power.
Microinverters versus String Inverters
Microinverters are relatively new when compared to the more conventional string inverters, but have gained a lot of popularity over the years and for good reasons. Many practical issues encountered with solar installations make microinverters a better choice, which include shading issues, multiple array configurations on a given roof, future expandability, and the ability to provide individual solar panel telemetry. There are cases where string inverters are desirable, so we will cover the advantage/disadvantages of both systems.
String (Centralized) inverters require a string of solar panels (typically connected in series like batteries in a toy) to create a larger DC voltage (as high as 600VDC). This high voltage is sent from the solar panels through conduit to the string inverter (located near your service panel) where it is converted to AC. It is important that all panels connected in the string output are matched, otherwise the entire string may be degraded by one or more panels dropping in power output due to shading or other types of degradation. Unfortunately, even identical panels have a manufacturing tolerance that can reduce the ideal output due to mismatch.
A new product from SolarEdge, called Power Optimizers (placed between each solar panel and the main DC power), claim to optimize panel power output through MPPT and address shading issue problems associated with conventional string-based systems. This solution also allows for panel telemetry, which is great for those like me who want to monitor the output and health of each solar panel. Only time will tell if this option becomes a viable cost-effective and reliable solution that can compete with the current microinverters.
Since these systems have a single, high power inverter that is easily accessible, maintenance and service is simplified. In addition, they are typically cheaper overall and are not subjected to higher thermal swings when compared with microinverters installed on the roof. On the downside, they take up space usually near your power panel and can make some noise while operating.
The advantage of microinverters is that each solar panel converts its DC (direct-current) to utility-friendly AC (alternating-current) right at the panel. If any single panel encounters a decrease in output due to shading, debris, or life degradation, it does not affect the output of the other panels in the system. In addition, microinverters allow for easy expandability and provides individual telemetry from each solar panel installed in the system as opposed to only being able to monitor the entire system in the case of a string inverter-based system. My installation requires two separate solar arrays located on different parts of my roof, which also has to deal with seasonal shading issues. This and the ability to easily scale up in power (adding additional panels/microinverters) was a big reason why I chose to go with Enphase M215 microinverters. Although Enphase has recently introduced the new M250, which is said to be a higher powered version of the M215, it has yet to be proven in the field. Only time will tell if the new design will be as reliable as the M215.
The Enphase M215 is a proven product that has been around for more than 2 years now. Recently, Enphase launched their new fourth generation M250 microinverter, which leverages heavily on the much proven M215 design. The new M250 offers a slight increase in efficiency (96.5% versus 96%) over its predecessor with an increase in output power capability.
The only real limitation of the M215 is that it peaks out at around 225 Watts. When using higher power solar panels (rated at > 250W), users may sometimes experience power clipping where the inverter reaches its maximum output capability. Although it seldom occurs, power is wasted during this time
New Enphase M215 Released
Enphase is now shipping a new version of the proven M215 Microinverter. Unfortunately, we missed getting this product installed. This new M215 offers the benefits of the world’s most advanced microinverter technology – including Integrated Ground (IG) and higher CEC efficiency of 96.5% – to systems using PV modules up to 270W.
Utility Voltage/Frequency Monitoring
The Enphase microinverters monitor the AC voltage and frequency coming from the utility and when the microinverter detects a voltage or frequency out of range condition, it must remain offline until the utility has been within acceptable limits a short period of time (several minutes, varies by region). If during that time the utility again exceeds or falls short of acceptable limits, a five-minute timer must restart and the microinverter may not begin producing power for an additional short period following the last out-of-bounds condition. Therefore, it is not possible for the microinverters to produce power when the utility power goes down.
Many customers are worried about their roofs when getting solar installed. In my case, our roof has composite shingles that are about 15 years old. As a homeowner, the drilling I heard during the installation worried me, but upon inspection I noticed that each mount was neatly tucked under the above shingle to prevent water from running under the mount. Only time will tell how well this works, but it certainly passed the visual test.
The rails were then installed on the mounts and cut to size. The first array consisted of 13 panels on the back side of the roof. Each microinverter is mounted to the railing under each of the solar panels and is connected to the trunk cable. The trunk cable is designed to provide proper connector spacing for portrait or landscape panel configurations. The second array consisted of 16 panels on the front side of the roof. The two arrays sent power separately to the sub-panel.
Unfortunately, we soon found out that the 200A panel upgrade would require trenching a new power line from the street, which could run into an additional cost of $8K to $12K. This would significantly increase the total system cost, extending the payback period. Luckily, we were able to upgrade to a new 125A power panel using the existing 2-1/2 conduit, which worked out great while keeping within the cost baseline. What I also found out as we moved ahead was the 290W LG panels we had initially planned to install were in short supply, so we went with (29 instead of 26) LG 260W panels, which gave me the same net power with a slight increase in roofing real estate. Again, this change did not affect the baseline quote for the system. Just make sure that you are getting quality solar panels and not the cheaper Chinese models that can have long-term quality issues. The 29 LG panels (in 2 arrays) were installed in 2 days with some minor electrical work done on the 3rd day. A crew of 4 worked the 1st day and 5 worked the 2nd day. I decided to have the proven Enphase M215 microinverters installed on the 1st array (16 panels) and the newer M250 microinverters installed on the 2nd array (13 panels). This allows us to compare the performance of the two (M215/M250) microinverter designs.
Solar Power Breakers
The sub-panel and cut-off switch were also installed during this time. Each solar array has has a dedicated set of AWG 10 power lines feeding separate breaker circuits, allowing complete control of the system. The two feeds are then combined and sent over AWG 8 wire to a single cut-off switch that is also metered. This allows me to independently monitor the solar system power at any given time. The electrician (Vardan) was excellent and answered all of my questions as the job was being done. He completely replaced my old power panel and installed a set of new breakers in under 5 hours. The new panel looks fantastic. I have worked with a lot of contractors in the past and I must say that LA Solar Group has been one of the best experiences I have had. Even with the crazy end-of-the-year (2013) rush to get installs done (to receive the 30% tax credit), they delivered in a timely manner. The City of Torrance recently approved the work (fire department, building & safety, and electrical inspections). As of 2/7/2014, we received PTO (permission to operate) from SCE to flip the switch on so we can back-feed into the grid. From the time I signed the contract with James (late October) to when the system went live was almost 4 months. This was somewhat delayed by SCE getting out to the site to check on the power panel feed for the upgrade. Apparently, we had a record PTO time from SCE once we received city approvals (less than 2 weeks) thanks to Ara aggressively working this.
The power panel required a significant amount of stucco to be removed from the walls as part of the panel upgrade. LA Solar Group did a great job on the stucco and matching my house paint. They also painted all of the conduit under the roof eaves to match the house paint. This level of detail does not go unnoticed.
Time Lapse Video
To capture the installation process and help potential customers see what a typical installation process consists of, I installed a video camera to record the action. This video compresses 8 hours of labor into 2 minutes. This is the front side roof where 16 panels were installed. An additional 13 panels on the back side of the roof were also installed, but are not shown here. Notice the installers anchor themselves with fall arrestors to prevent injury in the even they fall off the roof.
Once the installation is complete, the site will need to be checked by the fire department (for roof access), building & safety, and an electrical inspector. It is best to check with your solar installer to make sure that they have worked with your city in the past. Otherwise, you may run into specific code issues, which can ultimately cause delays in approvals and time wasted in getting your system up and running.
One of the advantages of using Enphase's microinverters is that each and every solar panel/microinverter can be monitored for performance using Enphase's Envoy communications
gateway. The Envoy unit can be plugged into any standard AC wall socket and
connected via an ethernet cable to a broadband router or switch. Enphase recommends placing the power interface close to the main power panel to maximize the signal strength to the microinverters. However, in practice we found that it is best to test for signal strength in different locations. Our closest outlet to the main panel had the worst signal strength while a nearby room had 4 out of 5 signal bars. The solar panel data
from the connected microinverters is collected by the Enphase Envoy and transmitted to the Enphase
Enlighten website for analysis.
One of the advantages of using Enphase microinverters it the ability to monitor your solar system health. Data collected by the Envoy is processed by Enphase and is available to the system owner (and the installer). The View tab shows the layout of the panels on the roof relative to North being up. Users can see the power performance (current, daily, weekly, monthly, lifetime, or custom time) of each panel as well as the performance of the entire system. Zooming in and out is easy using the scroll wheel on the mouse or the zoom selector on the screen. Also, the color of each panel changes based on output. The lighter the color, the more power being produced by the panel. This gives the user a quick way to visually see the performance of the system and identify any shading problems or system performance issues.
The Graph tab provides power output as a function of time. This data can be used to trend the amount of power produced from sunrise to sunset. Clouds passing over will drop output power immediately and may show up on the plot depending on the duration. Users can also plot the performance of an individual microinverter in the system, which is useful if shading is a problem. For example, you may see a consistent dropout in power during a certain time of the day due to a (chimney or tree) shadow walking across the roof and it will be easy to identify using the Enlighten website.
Data for each individual microinverter (power, DC voltage, DC current, AC voltage, AC frequency, and temperature) can be examined for performance over a period of time. This can be helpful in determining any performance issues with the solar panel or microinverter. The graphs can also help users determine shading issues on panels that are not on par with other panels in the system. This data also allows Enphase to see how well their microinverters are performing in the field. It makes it much easier to rectify performance issues related to their products should there be a problem with a microinverter over the 25-year warranty period.
I'll admit that I like watching real-time data as well as trending data to see how well a system is performing. While the Enphase Envoy is very powerful, it does not update as fast as some power monitoring systems connected directly to the solar feeds. A product called TED (The Energy Detective) uses a pair of non-conductive current probes to send data over the power lines, similar to Enphase microinverters. So far, I have not seen any data conflicts and both systems seem to work well. I have two TED (Model 1001) meters monitoring my HVAC power as well as my solar power. I get real-time data (updated every few seconds) that I can see when power changes. I can literally see the sun break through the clouds and watch the solar power jump up several kilo-Watts - very cool.
Smart Meter Monitoring
Another great product that I found useful is the Ecobee Smart Si thermostat with the Zigbee interface module. This smart thermostat not only has WiFi built in for remote access and control of your heating and air conditioning, but can also link to your SCE smart meter for collecting power data. SCE will actually give its customers $125 rebate ($50 for the thermostat and $75 for the installation) for installing the system. The device is registered with SCE through their HAN (home and business area network) website. The data collected is available at the Ecobee website (with user login) and has the power data available shortly after it is collected. SCE also has the power usage data, but it is usually delayed by at least a day. Here you can see the solar system produce more power than what is being consumed, which pushes the meter backwards. Unfortunately, negative power is not displayed in the graph.
People considering PV solar power should do the math to determine how long it will take to break even. While the initial investment is significant, the long-term investment makes sense if your electric bills are pushing you into the high tiers. My calculations estimate a break even point at around 8 years, depending on the weather. Here in the photo is a good day when the solar system generated more power than what was used that day. The good news is those taking advantage of the financial incentives provided by the California Solar Initiative (CSI) require new components certified by the California Energy Commission (CEC) and must have carry a minimum 10-year warranty. Installers in California are required to provide the warranty. The major components of this system include the solar panels (LG has a 10 year warranty) and the micro inverters (Enphase has a 25 year warranty for the M215/M250).
Watching your smart meter run backwards is exciting, especially when you consider it will occur daily when the sun is present. Even though I had initially wanted the newly released Enphase M250 microinverters with the 290W LG solar panels, availability was an issue on the panels. After much thought, I went with the lower 260W LG panels (29 instead of 26) since they were available and mated them to the Enphase M215/M250 microinverters. Ara convinced me (and that's not easy) that the M215's have a proven reliability record and I would be taking somewhat of a risk with the unproven M250's. Since I wanted to see both in action, we decided that it makes sense to install both to get a good comparison. My only caution to potential customers is you may not end up with exactly what you initially wanted (if you are as picky as I am) due to availability, so plan accordingly. The cost per watt remained the same, so in the end this wasn't a big issue for me.
Surprisingly, while California is the biggest solar state in the USA, it only ranks #12 in solar-friendliness (based on net-metering policies, tax credits, rebates, interconnection regulations, etc.). Hopefully, California will soon pass legislation to standardize residential solar permitting, which will ultimately reduce the installation cost and streamline the painful permitting/approval process endured by do-it-yourselfers and folks like LA Solar Group.
For those interested, The California Solar Rights Act states
(a) The implementation of consistent statewide standards to achieve the timely and cost effective installation of solar energy systems is not a municipal affair, as that term is used in
Section 5 of Article XI of the California Constitution, but is instead a matter of statewide concern. It is the intent of the Legislature that local agencies not adopt ordinances that create unreasonable barriers to the installation of solar energy systems, including, but not limited to,
design review for aesthetic purposes, and not unreasonably restrict the ability of homeowners
and agricultural and business concerns to install solar energy systems. It is the policy of the state to promote and encourage the use of solar energy systems and to limit obstacles to their
use. It is the intent of the Legislature that local agencies comply not only with the language of
this section, but also the legislative intent to encourage the installation of solar energy systems
by removing obstacles to, and minimizing costs of, permitting for such systems.
I have to say that as picky as I have been with this solar installation, I am very pleased with the quality and speed of the work and above all the results of the end product. The staff at LA Solar Group is exceptional and they are customer focused. Each and every person I dealt with from the company (total of 10+) had a great attitude and was pleasant to work with. More specifically, Ara Petrosyan has been the best, providing me full support and answering all of my questions and requests throughout the entire installation process. I would highly recommend LA Solar Group to my friends and colleagues.
My solar system has been in operation for 9 months now with well over 10 megaWatt hours of power generated. I am very happy with the performance of this system. I happen to be in a place where the sun sets behind a hill, so my power generation abruptly cuts out towards the end of the day affecting my overall power production by around 10%. Even so, I sized my system accordingly and based on my initial numbers, this system should pay for itself in about 6 to 7 years after factoring in the rebates and tax credits. On good days, I generate more power than I use and on average I seem to be close to breaking even. My bill last year at this time was around $250 and this year it is $2. Hopefully the trend continues, but only time will tell.
4-Tier Rate Plan
Choosing the best rate plan with SCE is also something solar users should look at once they receive permission to operate. The basic 4-tier (aka Domestic ET) rate plan charges based on the current tier you are at. Once you exceed your baseline by a certain percentage, you will move into the next tier and be billed at a higher rate per kWh for additional usage. When your solar system pushes power back into the grid, you will receive power credit at this same rate.
Time of Use Plan
SCE also offers a Time of Use plan (aka TOU-D-T) where the rates are based on the time of day, day of week and seasons. Peak rates occur week days from noon to 6pm while off-peak rates include week days 6pm to noon, weekends, and holidays. Summer rates start on June 1 and winter starts October 1. The off-peak rates are lower than the Domestic ET tier 1 rates, but the peak rates are similar to the Domestic tier 3 rates.
Based on my calculations of both a good and bad solar day, I benefited from going with the Time of Use (TOU-E-T rate). On days I generated a lot of extra power, my credits were much higher and even on days where I used more power than I generated, I paid less. I encourage users to run the numbers in a spreadsheet to convince themselves of any potential saving. We'll see how much better or worse the TOU-D-T plan is now that I have switched over, but based on the SCE website data, I already see a benefit. Currently, under this plan I have used more power than I have generated, yet I show a credit due to the amount of power generated during on-peak hours. Need more convincing before you switch?
Here is some info from the SCE TOU-D-T documents.
Southern California Edison’s (SCE) Time-of-Use Domestic Tiered (TOU-D-T) rate is a flexible choice that can help customers save money when they use energy wisely. With TOU-D-T, if you reduce on-peak energy usage,
or use renewable energy technologies (like solar generation), you may be able to lower your average electricity costs.
TOU-D-T: A WIN-WIN MONEY SAVER
- Are you an SCE residential customer?
- Do you use renewable energy technologies?
- Do you use a relatively low amount of energy, and use most of that energy during off-peak hours?
- Can you shift some of your energy use from weekdays between 10:00 a.m. and 6:00 p.m. to evenings (after 6:00 p.m.) and weekends?
If your answers are yes, TOU-D-T might be just what you need: money-saving, energy-smart and good for the environment.
If you enroll in TOU-D-T and use a lot of electricity during on-peak hours (weekdays between 10:00 a.m. and 6:00 p.m., when demand is high and Time-of-Use [TOU] rates are highest) you’ll pay more than you would during other TOU time periods.
But if you’re normally out of the house during workday hours, or if you can switch a few tasks (like laundry) to off-peak hours before 10:00 a.m., after 6:00 p.m. and on weekends, TOU-D-T may help you save money on electricity. No sacrifices — just savings.
Actual Output Power Differences between the M215 versus M250
This system has 16 M215's (1st gen) and another 13 M250's installed with the same 260W LG solar panels with the exact same azimuth and angle.
I wanted to compare the difference in output power between the two microinverters in a real-world case. The advantage of the M250 is that the peak output is about 25W more than the 1st generation M215. The M250 also has a slightly better efficiency rating (96.5% versus 96%) than the 1st generation M215. However, the M250's cost slightly more than the M215's and the difference in real-world output power may be so little that it is not worth the extra money.
Real Data as of Oct 2014
The cost of the M250's is more than the M215's and depending on your solar panel output, you may never see a real benefit. In my installation, I have noticed that my M215's peak at 225W and the M250's have gone as high as 235W in rare instances. If your panels never or rarely hit the peak (225W) M215 limit, it is really just a waste of money. Interestingly enough, the average power generated from the M215's is slightly higher (~3%) than the average power generated by the M250's. This is due to daily shading issues on the array that use the M250's and has nothing to due with the M250 performance. The point is you may or may not benefit from the more costly M250's. The plot above shows the lifetime power output of my 29 microinverters as of October 2014. The first 13 plots are the M250's followed by the 16 plots of the M215's. My advice would be not to go with the M250's unless your panels produce significantly more than 225W on a regular basis or if you are getting them at no additional cost in your system.
Los Angeles County has a Solar Map and Green Planning Tool website that is designed to look at your specific rooftop (via satellite imagery) and help you figure out whether solar is even worth the expense. In my case, the website indicated that my location was very poor for a solar project I would generate very little power. This may have been based on the surrounding trees and the hill where the sun sets. However, I was able to trim trees and get substantial power during the day, so I find the website a bit too conservative.
If you find this review useful or have any questions, send me an email. In addition, if you do decide to go with LA Solar Group based on my review, let me know and I'll send you specific contacts at LA Solar Group and you can get a discount on my referral.