Category: Solar Projects

Expanding Your Off-Grid Solar System? Here’s What You Need to Know

Expanding Your Off-Grid Solar System? Here’s What You Need to Know

JEREMY CHAMPT, Senior Sales Tech at Wholesale Solar​

There’s nothing quite like the sense of independence that comes from living off-grid.

But with that sense of freedom comes the responsibility of providing for your own energy needs – and it can be frustrating if your solar system struggles to supply power for the things you do on a daily basis.

You might find that your energy needs have evolved over time. Or maybe the system wasn’t sized to accommodate surges of heavy usage, and you need a little extra juice to cover peak output periods.

Thankfully, most off-grid systems can be expanded with additional panels, inverters, and a bigger battery bank.

When does it make sense to expand?

Before we tell you how to expand your off-grid system, you should work out why you need to add on to your system in the first place.

There are a few situations where modular expansion makes sense:

  • Budget constraints. It’s fine to start with a small system, then expand in the future as your budget allows.
  • Increased energy consumption. Your energy usage can change if more people move on to the property, or you buy more stuff that needs to be powered.
  • Insufficient solar production. If your system wasn’t sized to account for high-usage periods, it might need a few tweaks.

Budget Constraints

An off-grid solar system is a big purchase. Not everyone has the cash on hand to buy a system that will cover 100% of their energy needs.

Fortunately, you can build your system in small installments rather than make one large purchase outright. It’s a great way to approach your off-grid installation  but it requires a bit of planning in advance.

Our designers always recommend building a system with future expansion in mind. Regardless of whether you choose a roof-mount or ground-mount racking system, make sure your setup leaves space to tack on extra panels.

You should also be aware that inverters and batteries have their own capacity limits. If you add more panels, you’ll likely pair them with new inverters and batteries to keep pace with the extra output.

Not sure what size system you need? Calculate an estimate here.

On the flip side, it’s also worth considering how much more expensive this piecemeal installation method can be the long run. You should be aware of the drawbacks of building a system step-by-step:

  1. Panel Consistency

If you go years between additions to the system, it could be challenging to find panels that are the same make and model as your existing system. Solar tech advances rapidly, and companies update their product lines to keep in line with the latest innovations.

Thankfully, this is not too big of an issue. Most panels have a standard voltage and size, so a new panel will likely be compatible with an old system. There will be cosmetic differences, but a mix-and-match system should function just fine.

In general, it’s fine to mix and match panels as long as they are within 1 volt. Electrical specs and sizes are standardized (60-cell and 72-cell panels are common). For example, if you have 60-cell panels, you’ll be able to expand with more 60-cell panels, regardless of make or model.

  1. Extra Installation Costs

When you purchase your system in installments, you end up paying a lot more in shipping and installation.

And if you’re working with a contractor, you’ll have to pay the same service fees twice. The labor always costs less if you can get the whole project done in one go.

But these surcharges are minor compared to the overall cost of the system. And it may be worth it to be able to break the purchase into installment payments.

And depending on your setup, you may be able to skip the contractor and handle any additions yourself.

The process for adding on new panels isn’t too complicated. It involves minor adjustments to the mounting hardware, like adding different clamps. Depending on the brand and frame size of your panels, you might be able to bolt it on to your existing hardware without any changes at all.

Do keep in mind that if you upgrade your system to produce more solar energy, you may also need to add another charge controller and make adjustments to your wiring so you don’t overload the existing circuitry. Electrical expansion can be complex and requires a healthy bit of knowledge and research or the aid of a certified electrician.

Our support rep Ricky learned first-hand that making wiring changes to his system was more challenging than it initially appeared. Read his story:

Going Off-Grid? Please Don’t Make the Same Battery Mistake I Did

Increased Energy Consumption

Sometimes your energy needs simply change over time, and you need to expand your system to keep up.

Did you install a well pump? Add a second refrigerator? Or maybe your household has grown recently  either new roommates or a new addition to the family  and you just need a bit more to cover the expanded usage.

In that case, you can add on to your existing solar system by purchasing more solar panels, inverters, or a battery bank expansion. It’s a great idea to talk to a DIY solar tech to understand which parts you’ll need to keep the system stable. If your current equipment isn’t on the market, they can recommend parts that are compatible with your current system.

Your Solar Panels Aren’t Producing Enough

If your panels aren’t putting out as much energy as you originally thought they would, the issue might not be related to the size of your system.

Other factors can contribute to lower energy output: temperature, shade, and the direction your panels are facing. Poor setup may cause an otherwise well-sized system to underproduce. In certain cases, reconfiguring your system can bring it up to its expected output.

Mounting Direction & Angle

If you live in the Northern Hemisphere, your panels should face true south. Facing panels directly into the sun during peak hours will maximize the energy you generate.

However, you can’t exactly change the orientation of the roof on a house you already live in. Many people have to settle for placement that’s “south-ish” or a split between east and west.

In this case, adding more panels is more cost-effective than trying to find the perfect orientation with your existing system. It doesn’t hurt to fine-tune your mounting orientation if you have an adjustable mount.

For a fixed tilt angle, your array should ideally be tilted at an angle approximately equal to your latitude, for optimal year-round production. If you use an adjustable pole mount, you can tilt to a steeper angle in the winter to optimize production throughout the year.

Realistically, it’s a lot of work to adjust mounts, and most people would rather leave it alone to avoid the hassle. But it is an option if space is limited and you need to squeeze that extra bit of efficiency out of your system.

Temperature & Location

Solar panels are rated at standard test conditions (STC). The tests are run in a controlled environment, with temperatures regulated to 77°F and an ideal amount of light shining down on the panels.

In reality, your living environment rarely matches these optimal conditions.

In fact, most panels produce about 10% less power than their rating due to heat, clouds, and other factors. A 300W panel might only put out around 270W on an average day. The maximum output is rarely achieved, except during clear sunny days with ideal conditions.

There is another rating system called PTC, which tries to account for real-world conditions. PTC ratings tend to give a more accurate picture of how panels will perform in the real world.

Before you size a system, take your local climate into account. Extreme climates translate into a larger knock on the rated efficiency of your system. Keep this in mind when sizing up an expansion for your solar array.


Solar panel production will be impacted by shade, and a few small shadows can have a big impact on your solar panel output. Solar panels need to be installed in full sunlight for optimal performance.

Some modern panels have features including bypass diodes and half cut cells that can help with shading. But if you are experiencing lower output, check to make sure the array is not being shaded throughout the day. Over time, it’s possible for trees to grow up and cast shade on your solar array, reducing its performance.

Also make sure your panels are clean from pollen, dust, leaves and other debris. Over time this can build up and start reducing performance if not cleaned off by rain and snow. Clean your solar panels with water and if needed, a small amount of mild detergent.

Aging Equipment

Over time, solar equipment will age and and drop in efficiency. Solar panels usually last for 30+ years, but the output decreases slightly every year. Most solar panels are guaranteed to produce 80% of their rated power after 25 years.

It could take years to notice the impact, but over time your panels and batteries will decline in efficiency. After 5-10 years, you may find that your production has dipped below your energy needs.

You should design your system to account for this efficiency drop. But if you didn’t take this into account from the start, it isn’t too hard to add parts to compensate for expected efficiency losses over the life of the system.

Adding To Your Off-Grid Solar Array

If you’re ready to move forward with an expansion, some of the easiest parts to add on to your solar system are the panels themselves. Most of the off-grid solar systems we sell have panels wired in strings of three. That means if you’re adding panels, you will do so in multiples of three (3, 6, 9, 12, etc.) – not one at a time.

Depending on your system, you may be able to add a few more panels to the existing charge controller(s). You could also install multiple charge controllers, but be aware: your battery bank can only handle a given amount of charge current. Eventually, if you add a lot of solar panels, you will have to upgrade your battery bank so that it can handle the additional influx of power.

Adding Panels To A Ground Mount

Because off-grid living is usually synonymous with wide-open spaces, many off-grid customers install a ground-mount system. Since you don’t have to climb on your roof to make adjustments, it’s very easy to bolt on new panels whenever you need.

This could work to your advantage if you plan to build your system over time. If you have the space, go with a ground-mount racking solution. You’ll have easy access to the system any time you need to make an addition or perform maintenance.

Adding Panels To A Roof Mount

In order to expand the solar array on the roof, you’ll have to add on more racking and connect the panels to the existing combiner box and charge controller, as long as it can carry the increased load of power.

Expanding a roof-mounted system can be a bit trickier, since space is limited. A portion of your roof may not provide a viable build space, if it faces the wrong direction or is covered in shade.

What happens if you run out of space on your roof?

The first option is to replace some modules with higher efficiency versions to bring you up to speed. If that’s not enough, you can also pair your solar array with an alternate power source like wind or hydropower. Be aware that these options are limited depending on access to local resources  it won’t be an efficient option in areas with low wind speeds or strong water currents.

Mixing and Matching Panels

Take care when mixing and matching old and new parts from different brands. As described in this article in Home Power:

“Solar panels have changed dramatically over the years…not that long ago, 80W 12V nominal modules were common; today, 200W (or larger)…are more typical.”

It is okay to mix and match panels, but make sure the new panels have the same or as close to the same operating voltage, watts, and amps possible.

For example, you could add a 270W panel to your existing array of 250W modules; both of these are 60-cell panels that operate at the same voltage. As long as the panel voltage is within 1 volt, the system will be fine.

Permitting & Code Compliance

Additional permitting may be required when you expand your system. Depending on the size of your expansion, you may have to have the plans approved by the authority having jurisdiction (AHJ) – in most cases, the county or city planning department.

Build your system by the books to avoid headaches down the line. Download our Solar Permitting Cheat Sheet to ensure your system is up to code.

Even if you’re off-grid and miles away from civilization, it never hurts to have all of your permitting taken care of. If you or your neighbor ever sell or appraise your land, permits will be useful to prove the system is built within your property lines and up to code.

All panels and equipment should ideally be certified by UL to be permitted in the U.S. UL is an organization that ensures PV equipment passes rigid safety and quality standards.

More Inverter Power!

Most of the off-grid inverters we sell are “stackable,” which means you can nest multiple inverters together for increased power output. This is especially useful if your usage increases over time and you need more power on tap.

Adding another inverter isn’t always simple. The circuit breakers and wiring in your system likely aren’t designed to support another inverter. In some cases, the entire inverter system may need to be rewired. But if you anticipate expansion when you build your system, expandable power centers are designed for this purpose. You can add extra inverters and rewire them to a central hub — no extra wiring necessary.

A bigger inverter may require a larger battery bank to handle the increased output. The inverter manual should indicate minimum battery bank size, typically 200-400 amp hours minimum per inverter.

Expanding Your Battery Bank

The process for expanding your battery bank depends on the type of battery you have – either lead acid or lithium.

When you add a new lead acid battery into an old bank, the new battery takes on the capacity and other characteristics of the existing batteries. When you add more batteries, they drain down to the level of the old ones.

This might not be a big deal if the battery bank is only a year old. But it’s usually it’s not a good idea to expand a lead acid bank after it’s been used for a several years. Simply put, your new batteries won’t hold as much power as they could when you mix them with older batteries.

This is one area where we recommend planning for extra capacity to future-proof your system. With proper maintenance, you can extend the life of lead acid batteries to 7-10 years. You don’t want to tack on more batteries halfway through and instantly have the new batteries run at sub-optimal efficiency.

You can increase your battery capacity by wiring in more batteries in a parallel circuit. A parallel circuit combines the positive and negative battery connections, to increase the current (in amp hours) while maintaining the same voltage.

Diagram showing series wiring versus parellel wiring

However, there is a limit on the number of lead acid battery strings that can be wired in parallel. Three parallel strings of batteries is the recommended maximum. One or two is more ideal: they will charge and discharge more evenly, which makes them last longer.

Lithium battery banks are easier to expand because there are built-in electronics to manage the battery charge and balancing. Certain off-grid lithium batteries can be expanded over time, including Simpliphi and Discover AES batteries.

If you’re pre-arranging your system for future expansion, lithium batteries are the more modular and expandable option.

They are also more efficient, safer and tend to last longer – which comes with a price premium, of course.

If you’re not sure where to start with your system expansion, our design techs can help you sort it out. Get in touch with a system designer to help ensure your upgrade is compatible and covers your increased energy needs.

Install of the Month – November 2017

Install of the Month – November 2017

“Going Big on Going Green” with Jeff Dickens

They say “go big or go home,” and that’s just what professional installer Jeff Dickens did for this month’s feature. He went big by going green with a full solar system on a commercial business, and the results are truly impressive. Mt. Shasta Animal Hospital is now powered by renewable energy thanks to his install.

I have worked with this customer in the past as he is a local installer.  He is one of the easiest electricians and solar installers that I have ever worked with. 
– Solar tech Jeremy Allen

This massive install was a huge undertaking, but the results can’t be ignored, and the benefit of offsetting the client’s power bill speaks for itself.

Interview with Jeff

What Solar System Type Did You Install?

I chose to install a grid-tied system to suit my client’s power needs.

What Was Your Primary Reason for Adding Solar to Your Home or Business?

My main goal was to provide green energy in a commercial business and to offset grid power consumption. The solar array I installed collects enough energy to power, and should help Mt. Shasta Animal Hospital save money month-to-month on their utilities.

Did you have any previous DIY experience?

Yes, I’m an electrical / solar contractor and have installed numerous systems. My experience in the industry allowed me to make this install go very smoothly.

What was the most difficult part of the installation?

An install on a roof like this, safety is your biggest concern. You need to be aware of your rope rigging and all safety measures taken. Sloped metal roofs can be extremely dangerous, so we took extra precautions with scaffolding, a man-lift, fall-prevention gear and waited for dry weather conditions to be as safe as possible. There was also a small snag with some of the permitting process, but we took care of it quickly.

Our wiring diagram had to be taken to a local electrical engineer to be stamped which was out of the ordinary, however did not slow down the process and was completed with only minimal additional cost. 

 – Solar tech  Jeremy Allen

How Many Helpers Did You Have?

I had two experienced workers helping with the install, who were also general contractors.

Did You Hire a Contractor?

Being a professional contractor, I always recommend at least consulting with a electrician or solar contractor before a DIY Install. It can save a lot of headaches. In this case, I was the contractor in question, hired by Mt. Shasta Animal Hospital to install their solar system. Wholesale Solar’s DIY systems make my job that much easier for a professional install.

Were There Any Unforeseen Additional Parts or Tools You Needed?

Not really. In the nuts and bolts category, a couple extra is always better than the exact amount.

How Long Was the Full Installation Process?

Start to finish for the complete install was about 7 days. The roof work to install racking and panels was 4 days. It took 3 days to complete all the electrical and setting the inverters.

How Did it Feel to Get Your Solar Project Finished?

The owners of the business are very happy with the install.

Who Else Did You Consider Before Choosing Wholesale Solar?

I only shop at Wholesale Solar.

How Much Did You Save On Your Taxes?

The client will save around $14,000 with the Federal Tax Credit and California’s state incentives combined.

Components in Jeff’s System

Questions about Jeff’s install? Ask us in the comments below.

Install of the Month – June 2016

Install of the Month – June 2016

Greetings Solar Fans, and welcome to the Wholesale Solar’s Install of the Month for June 2016. This incredible install is brought to you from the great state of Massachusetts. With the generous net metering policy, Solar Renewable Energy Credit incentive program, and 30% federal tax discount, Seth certainly installed at the right time!

Seth F purchased a 11.88kW Suniva/SolarEdge System utilizing 36 of the Suniva 330 Watt panels and one 11.4kW SolarEdge Inverter. (We’ve since modified that system to be an 13.6 kW Grid‑Tied Solar System with SolarEdge and 40x Suniva 340 Watt Panels) Although it’s simpler for us, and easier for you to use one of pre-packaged complete solar systems we can easily modify them to meet whatever roofing limitations, HOA requirements or permit requirements you might have.

The solar tech that helped Seth F put together his system was our very own Jeremy A. He reassured Seth that even though he was going on vacation before the install, Seth had the entire Wholesale Solar team behind him and we would be there for any questions or support he needed. They went over a number of different systems and what Seth’s requirements were and the system that was purchased was actually Jeremy’s first suggestion to the customer (What can we say, we know what we’re talking about!). Knowing that this is one of the highest value systems that we keep in stock he also knew that we have a ton of successful installs for the system under our belt and would be able to help Seth in any way he needed.

Even though it took more than a year to work out the details and ship the system to the customer, Jeremy said Seth was a real pleasure to work with and enjoyed how Seth was always looking forward to the next step.

Components In Seth F’s System

Interview with Seth F

How long was the full installation process from receiving your equipment to flipping the switch? How many people did it take?

The actual physical install took me (and two good friends) basically two weekends, with bits an bops during the week. After the install, the inspections and the meter swap took about two more weeks. The permitting and state approval took the most time, about 2 months. [Editorial: bet he wishes he’d gotten the SolarPro Pack to help with permitting!] I had two friends help me one at a time. I sat on the equipment for two months before actually starting the install.

Did you have any previous construction experience?

No professional construction experience but I’m a Ship’s Engineer by trade so I can figure most things out and I’m decent with my hands.

What was the most confusing or difficult part of the installation?

Installing the mounts and securing the panels so they were level and square.

Were there any unforeseen additional parts or tools you needed?

The electrical inspector pinged us on the labels. I had to order a much larger label kit. I purchased a pvc conduit bender to make it look clean. [Editorial: We recommend for your one stop shop for labels, stickers and placards.]

How/Why did you choose to self-install?

Much cheaper than hiring someone to do it

What was your primary reason for adding solar to your home?

To reduce my electric bill and carbon foot print

Congratulations Seth on the successful install and incredible home from all of us here at Wholesale Solar!

Install of the Month – April 2016

Install of the Month – April 2016

Wholesale Solar sales technician Leslie B said Craig W. had really done his homework and came to her extremely informed, knowing exactly what inverter system and size panel array he wanted which really streamlined the process. One of the few sticking points in an otherwise smooth process was getting his install approved by his HOA, but once that was accomplished the project moved very quickly, so if you are thinking of installing a PV System of your own and belong to an HOA, make sure you have that as part of your checklist!

  • 5 yr. ROI
  • Saved nearly $10k by going DIY!
  • Total installed cost $17k to cover his entire energy usage

Components In Craig W’s System

7.68 kW Grid‑Tied Solar System with SolarEdge and 24x SolarWorld 320 Panels (complete system)

SolarEdge SE7600A-US Inverter 

SolarWorld SW320 XL Silver Mono Solar Panel

A SolarEdge inverter is really the best option for large 72-cell panels like the SW320s. SolarEdge can work with high power modules and unlike a micro-inverter it won’t limit the power output from each panel. Large panels are popular because the cost is lower and there is less equipment to mount — fewer panels, less racking and fewer attachments to the roof top.

Interview with Craig W

He’s been interested in solar technology since 1981 when he solicited a bid for a solar system for his first home. The 23 year payback at the time was a no go.  [editorial note: The cost of solar has fallen from nearly $30/watt in 1981 to less then 70 cents today! His current ROI will be around 5 yrs.]

How long was the full installation process from receiving your equipment to flipping the switch?

Four bids and 35 years later, with the help and advice from Wholesale Solar I finally have a system designed for Net Zero metering with a little extra for expansion (maybe an electric car charger, electric hot water on demand, or even second fridge in the garage?!) System specs: 7.8kW/ 24 Solar World Panels ,24 Optimizers and 1 Solar Edge 7600 Inverter

How many people did it take?

Once I decided to go forward with the project as a D.I.Y., I hired a consultant who provided me with a total of two hours of answered questions, spread over a month, to learn about the equipment and the terminology. Then it was time to go shopping. When I discovered Wholesale Solar’s numerous packages, competitive pricing and a treasure trove of educational material, it was considerably easier to choose a Complete Grid-tied system that fit our electrical needs and our budget (investment.) The numbers: based on current electrical charges of approx. $2,400 a year  ( PG&E ) and utilizing the Federal tax credit, the return on investment ( ROI ) will be 5 years or less.  For a total cost of  under $17,000.00 for the system (incl. labor, materials and permits) which was nearly $10,000 less than his lowest bid for purchasing elsewhere!! [editorial note: try our Solar Cost Calculator for yourself!] I  put together a homeowner application for the required County permits and had no problems submitting my file. I got the job site permits that same day.

Did you have any previous construction experience?

I  hired two referred, experienced installers who took on our home as a side job. My son Gavin, newly certified as an installer, joined in and  myself with many years of construction experience, and together we made up a perfect team. We installed the system as designed over a three day weekend as planned, like any professional crew. It was an exciting and worthwhile endeavor in every respect!

I spent a few hundred getting some trees cut back, eliminating morning and afternoon shadows, maximizing the efficiency of the array by another 10% and I was ready to go…..

That left only a final submission of paperwork to the county and PG&E for final permits and permissions as well as an application to my HOA, for a thumbs up on a request for a variance.. (granted). After that it was only a week before PTO (permission to operate) was given, and I was at long last, a micro utility!

Finally thrilled to be part of the solution and most of my appreciation goes to Leslie Benton, with an added assist from Cheyenne and Geri. You all provided excellent customer care and support, displayed unlimited patience for a demanding customer and helped my wife and I complete our last big home improvement project. Thanks for everything Wholesale Solar!

Solar Plane Ready to Resume Round-the-World Flight

Solar Plane Ready to Resume Round-the-World Flight

The Solar Impulse 2 is ready to resume her round-the-world flight after wintering over in Hawaii. Late in 2015, after completing a record 117 hours of continuous flight, the solar-powered airplane was forced to land in Hawaii for emergency maintenance on its battery bank.

A new cooling system was installed and a few test flights later, the Solar Impulse is ready to take to the sunny skies again the next time weather allows. Last year, it took 8 months to complete the first half of her journey from Abu Dhabi west through the Mediterranean, across the Atlantic, over the Americas and halfway over the Pacific. The next part of her journey is over the rest of the ocean, across Asia, and back to Abu Dhabi in the United Arab Emirates.

For more about the update, see the Solar Impulse Blog entry: Solar Impulse re-enters “Mission Mode”. Or learn more about this solar-powered round-the-world journey on the Solar Impulse website.

Installation of the Month – October 2015

Installation of the Month – October 2015

Interview with Dennis R.

How long was the full installation process from receiving your equipment to flipping the switch?
The equipment shipped about the end of July and I had to do some research to determine the proper roof installation (i.e., how the rails were to be installed, distances between rails, installation of the trunk line, etc.). I have never even seen this type of equipment, much less installed it, so when it arrived, I had to inventory it, read the installation instructions, then determine the best layout.

Read More Read More

Introducing Our Customer Installation of the Month

Introducing Our Customer Installation of the Month


Submit your installation photos for a chance to be featured.

Installation Of The Month

Starting in March 2015, Wholesale Solar will be selecting one of our awesome customers per month to feature in our Installation of the Month. We are constantly amazed by the installation photos we receive from customers, so in order to show off some of your beautiful systems, we are going to highlight one every month on our website, blog and newsletter!

Whether you have installed two panels or two hundred, send us some pictures of your work-in-progress or completed system and it could be featured. In return for taking the extra time to help inspire future Do-It-Yourselfers, we’ll be sure to send the Installation Of The Month winner some Wholesale Solar goodies.

For extra inspiration, look at some of the systems in our customer gallery.

Want to participate? Send a few photos and a brief description about your project to [email protected]. Even if you’re not selected for the Installation of the Month, we’d love to add you to our Wholesale Solar customer gallery so you can show your new system off to all your friends!

Last Chance for the 2011 30% Federal Solar Tax Credit

Last Chance for the 2011 30% Federal Solar Tax Credit

Gridtied SystemIf you buy a solar power center before the end of the year, your equipment and installation costs will qualify for the 2011 Federal Tax Credit.

What types of systems qualify for 30% Federal Tax Credit?

What do I need to know about the 30% Federal Tax Credit?


Solyndra, Innovators or Crooks?

Solyndra, Innovators or Crooks?

Solyndra had a great idea. They developed solar technology that promised to be cheaper than silicon. The Department of Energy believed in the venture enough to loan $500 millions dollars of Recovery Act funding. Private investors put their money down, too. They didn’t foresee that the cost of silicon would drop sharply and that China would ramp up and produce super low-cost silicon PV.  And, of course, they didn’t foresee that they would go bankrupt.

Piggy Bank
Is Solyndra a prime example of the government wasting our tax dollars?

Is Solyndra a prime example of government wasting your tax dollars on renewable energy?  Many folks have been making this claim. But do they know that Solyndra is only a tiny fraction of Department of Energy’s green-energy loan program, and that it is the only DOE loan to default so far? Solyndra’s loan guarantees are also infinitesimal compared to those of both fossil fuel and nuclear companies. Investigations reveal that there was no real scandal in the loan process. It’s also normal to have a certain fraction of speculative programs like this fail.

What happened with Solyndra actually points to positive change. Competition in solar technology has become so fierce that we are fast fowarding to the day when the cost of solar power will equal the cost of electricity from our utility company.

There is a lot of talk lately about Moore’s Law in regards to solar. In the computer technology field, Moore’s law says that the number of components that can be placed on a chip doubles every 18 months. According to Scientific American, if Moore’s Law were applied to solar power technology, we would eventually have the solar equivalent of an iPhone—very cheap, mass produced energy technology many times more effective than the giant and centralized technologies it was came from.Solar PV Cost per Kwh

Over the span of thirty years, the cost of solar cells has reduced 7 percent each year on average. If this continues, the cost of solar will be just over 50 cents  per watt in 20 years. PV modules historically have been about half the installed cost of a solar power system. With the cost of installation falling at the same rate as solar panels, the cost of solar in the U.S. will cross the current average retail electricity price of 12 cents per kilowatt hour in 2020. In fact, given that electricity prices are currently rising a small fraction per year, prices will probably cross earlier, around 2018 for the country as a whole, and as early as 2015 for the sunniest parts of America. Read more.

Solyndra was blindsided by a field that’s growing exponentially.  It’s clear to us now that solar power is here to stay.

The Effect of Shade on Solar Panels

The Effect of Shade on Solar Panels

Just a little shade can affect a solar panel ‘s power output dramatically. Diffuse shade from a “soft” source, like a distant tree branch or cloud can significantly reduce the amount of light reaching a solar panel’s cells. “Hard” sources stop light from reaching solar cells, such as debri or bird dropping sitting on top of the panel. If even one full cell is hard shaded, the voltage of a solar panel drops to half in order to protect itself. If enough cells are hard shaded, the module will not convert any energy and will, in fact, become a significant drain of energy on the entire system over time.

Partial Shading of Cells on a Solar Panel
Partial cell shading that reduce solar panel power by half.

Partial shading of even one cell on a 36-cell solar panel will reduce its power output. Because all cells are connected in a series string, the weakest cell will bring the others down to its reduced power level. Therefore, whether half of one cell is shaded, or half a row of cells is shaded, the power decrease will be the same and proportional to the percentage of area shaded, in this case 50 percent.

When a full cell is shaded, it can use energy produced by the remainder of the cells, and trigger the solar panel to protect itself. The solar panel will route the power around that series string. If even one full cell in a series string is shaded, as seen on the right, it will most likely cause the module to reduce its power level to half of its full available value. If a row of cells at the bottom of a solar panel is fully shaded, the power output may drop to zero. The best way to avoid a drop in output power is to avoid shading whenever possible.

A solar panel affects an array in much the same way a single cell affects a solar panel. In a centralized inverter system, where panels are strung in series, if only one of the solar panels is shaded in an array, the rest of the solar panels’ output diminishes.

When choosing a grid tie solar power system for their home or business, folks often prefer the tried and true technology of a centralized inverter systems. And the price tag on these is pretty good. When you consider the effects of shading, however, it’s easy to understand how microinverter and SolarEdge systems have become so popular.

While using different technologies, both SolarEdge and Microinverter systems allow each solar panel in an array to maximize power output independently, thereby maximizing a system’s power generation. If one solar panel is shaded in either of these systems, the rest of the array’s panels can still operate at full capacity. (SolarEdge provides DC to DC power optimization for each solar panel, while microinverters provide DC to AC optimization at the module level.) Both of these systems allow solar panels to be facing different orientations giving you more design flexibility if part of your installation site is in the shade. A centralized inverter system requires panels to facing the same direction.

Read more about SolarEdge, Enphase Microinverter and Centralized Inverter Systems.