Maryland Solar Company
Written by admin

Interesting Facts about Solar Energy

Maryland Solar CompanySolar energy as a topic is quite interesting. What follows are some fun facts that should increase your knowledge on the subject.

  1. Solar energy comes directly from the natural energy that is generated by the sun.
  2. It takes the sun’s rays eight minutes to travel through space and reach the earth’s atmosphere.
  3. Solar cells are designed to capture solar radiation and change it into electricity. This electricity is used to power homes and businesses.
  4. Most solar panels face south in the United States. It is the optimal position for capturing solar radiation.
  5. Even when the sun is not shining you can still use solar energy to power homes and businesses. That’s because solar cells are able to store energy for later use.
  6. Solar power is simply the most eco-friendly, inexpensive and safest form of energy on the planet.
  7. Solar energy, in the form of solar panels, solar batteries and solar cells, can be used to run everything from central air conditioning to a houseful of electronics.
  8. According to one expert it is possible to power the entire earth with solar energy, making the planet reliant solely on renewable (and clean) energy. To do this, solar panels would have to be installed on a little less than 200,000 square miles of land. While this may sound like too big a challenge – consider the fact that there are 57 million square miles of land on the entire earth and it is apparent the project is quite doable, with room to spare.
  9. There are numerous health benefits that come with the utilization of solar energy. First and foremost, it does not have pollution as a byproduct. The only time there is any pollution generated is during the manufacturing of the solar panels themselves. This is important to note because the production and use of all other forms of energy cause pollution in several forms – either in emissions into the air, as runoff into our groundwater, and the desecration of natural, nonrenewable resources.
  10. While you can purchase the solar system outright, that is not the only option for accessing this energy resource. There are instances where it is possible to rent or otherwise finance a solar system.

Solar Energy Services is happy to add to the knowledge base of visitors to our blog. We are proud of our reputation of meticulous installation for our residential and commercial customers. If you are in the market for solar services we hope you will give us a call!

 

Solar Service, Home Solar Panels ,Washington DC ,Solar
Written by admin

What the Experts Say about Solar Energy

Solar Service, Home Solar Panels ,Washington DC ,SolarAt some point we all devote our working lives to a cause, or the development of a skill-set that will be used to make a living. This is true for people who avidly study and report on all aspects of solar energy. Their opinions are important to the future of solar energy in this country, and the world, and will impact each of us. In light of this, let us consider the perspectives of solar power authorities.

During a presentation to the European Photovoltaic Solar Energy Conference a decade ago, the chairman of this organization spoke to the audience, declaring that solar energy has the ability to meet all the world’s energy demands. After all, the sun shines everywhere on this earth for part of the day, on land and water, and is both a safe, almost limitless, and clean energy source.

However, at that time, solar power had only provided a negligible contribution to the world’s energy supply.

Now, a full ten years later, resources have been marshaled, perspectives honed, and one report was recently released that projected the outlook for energy into the year 2040. First, qualified professionals predict the global energy demands will continue to rise on par with the increasing prosperity and improved living standards expected to be accessible to larger numbers of people in the world.

According to multiple sources, the global population itself will grow, perhaps exponentially, and as a result, there will be a growing need to accommodate this. Renewables now account for two-thirds of the new power that is being added annually to the world’s power grid, and solar energy is the fastest growing source of this!

In other words, solar capacity has significantly outpaced all other forms of energy development, particularly nonrenewable resources, but other renewable outlets (such as wind and water) as well. There are a variety of reasons for this, including changing government policies that are favorable to solar companies, and the decreasing costs associated with the development and manufacturing of solar power related equipment.

Solar Energy Services is proud to be a part of an industry that respects and preserves our natural environment today, and tomorrow. We are experienced in all aspects of the residential and commercial development and installation of solar panels and associated equipment. We look forward to serving you.

Maryland Solar Company,Solar services
Written by admin

Be Solar Savvy

Maryland Solar Company,Solar servicesThe most abundant source of raw energy is neither coal nor gas. It is not wood, wind, or even water. Look up and you will see a power generator without an equal – the sun! Scientists expect the sun to burn out in approximately 5 billion years. That means it should be able to generate kilowatts for homes, schools, and businesses over the next few decades at least!

Solar energy has developed into a variety of applications across the residential and commercial spectrum. Today, it is used to heat water for homes and pools through the solar thermal process. As well, solar power is collected in photovoltaic devices that then directly generate electricity using sunlight and semi-conductors.

Under the circumstances, it seems odd that mankind has not attempted to harness this limitless wellspring of electricity. Perhaps that is because collecting and converting the sun’s rays to usable current has been an intellectual challenge in the past. However, in recent decades, science and technology have collaborated to create a foundation whereby it can truly be possible for solar energy to become the single largest conductivity system on the planet.

Imagine never having to dip into our nonrenewable resources again. Imagine clean energy that leaves no waste byproduct. Imagine a form of power that does not decimate the earth, and does not make vast areas uninhabitable due to the disregard for the environment that often accompanies the collection of power resources such as gas and coal.

Solar Energy Services is here to make this possibility a reality. Our company has been serving the Washington D. C. and Maryland area for the past thirty-five years meeting our residential and business customers’ needs. Our solar design laboratory and separate headquarter offices are both located in Maryland. We are proud to be a vital member of the communities in which we are located. It is our mission to employ those who live in our area.

So, if you or someone you know is considering a solar panel project, please contact us. We are confident of our ability to meet the most diverse, and sophisticated needs.

Residential Solar Panels, Solar Service
Written by admin

A Primer on Solar Power

Residential Solar Panels, Solar ServiceDid you know that attempts to harness the sun’s power through the development of solar cells dates back to the late 1800’s? I am sure that this, and other information, may be new to our readers. This article will provide you with some basic facts about solar power and solar energy. That way, you can join the conversation, and the renewable energy movement!

The first successful solar cell was developed in the early 1950s. It was made of silicon, and able to power small electronic devices. This was hailed as the beginning of a new era of energy resources, even then being acknowledged as having the potential to offer a limitless supply of electricity.

The first true application of solar cells could be found in the space program at NASA and in Russia. They were the only ones who could afford this technology in the 1960s.

The cost of solar cells continued to decline incrementally, but not so significantly that solar was a common source of energy through the 1970s. But, as the 1980s dawned, and ever since, solar power has insinuated itself into all aspects of life, commercially and residentially.

The first solar panels for buildings were developed in the early 1970s. In truth, this initial foray into the potential for large scale residential solar power was actually a solar array built into a rooftop. Panel development followed, as the cost and manufacturing efficiency increased.

President Jimmy Carter had solar panels placed on the roof of the White House in 1979. Everyone was getting into the act!

Welcome to 2018. Today it is common to find solar-powered cars, solar-powered telecommunications, and even solar-powered aircraft. One car company, renowned for their progressiveness, has incorporated solar panels into the roofs of their vehicles!

But, there’s more! Technology continues to expand the horizons of solar energy, making it affordable and applicable in new ways and new places. For example, it is possible that eventually solar panels on rooftops will be replaced with solar shingles!

Or, consider this, a solar fabric is being finalized that can be attached to houses as a cooling device!

We here at Solar Energy Services are excited about the future applications of this renewable source of energy for personal and commercial uses. You can count on us to utilize our superior knowledge and expertise to your advantage. We look forward to serving you!

Solar Service,Commercial Solar Service
Written by Lisa Walsh

The Fairytale of the 25 year Solar Workmanship Warranty

Commercial Solar Service,Solar ServiceIf you’re like most solar shoppers, you prefer two or three bids on a substantial home improvement project; enabling you to sanity-check pricing, design options and find the overall best contractor-fit.  Included in these proposal comparisons is the Warranty. Most solar systems come with 3 warranties:

  1. Solar module manufacturer’s warranty; usually 25 – 30 years,
  2. Inverter(s) manufacturer’s warranty; usually 10 – 25 years (inverters convert DC energy to home-accessible AC energy)
  3. Workmanship warranty – entirely separate from 1 & 2 above. This insures the design and installation, insofar as contractor/labor portion of your install is covered for a given period of time, as determined by the installation company.

Industry Standard

As the popularity of solar has increased – so has the number of competing contractors and their accompanying solar proposals. All of these proposals should include a workmanship warranty. What will differ is the duration of the workmanship warranty. The standard duration for a residential solar system was always 5 – 10 years until a couple of years ago when some contractors started offering an unprecedented 25-year workmanship warranty. This is a good thing, right? On paper…sure.

Compete only to Beat

With over 35 years in the solar industry, it’s fair to say we’ve seen a lot of solar installers come and go; especially in the last five years. The go-ing usually brings with it a slew of phone calls to our service department as solar system owners panic about no longer having their contractor around to honor the workmanship warranty; particularly those looking to resolve existing issues. Ironically, these are sometimes homeowners that chose the contractor over us due to a workmanship warranty of shorter duration. We have stuck with the industry-standard of 10 years, whereas some other installers have increased to 25 years to match the manufacturer warranties.

So, the big question – and the reason for this current article is – Why? If some of our competitors are offering a 25-year warranty – why don’t we? Seems only natural, given the fact that we’ve been in business for longer than 99% of them – greatly increasing the probability that we’ll be around to honor an extended workmanship warranty.

The Big Answer (in two parts)

  1. We’re keeping it Real: Understandably, a 25-year workmanship warranty is attractive to a homeowner because – by design – it matches the 25-year solar panel warranty. This does not change the fact that a workmanship warranty exists entirely independent of the installed equipment warranty(s). A contractor’s history, fiscal health and future plans have little or nothing to do with the equipment warranties. Given this, we avoid inflating the language in our contracts to provide misleading comfort to a home or business owner, with the sole purpose of beating out the competition at contract-signing time.
  1. We’re still keeping it Real: Of all the orphaned solar projects we’ve come across – we cannot cite a single known instance where a homeowner has taken legal action over an abandoned workmanship warranty item; simply not worth the court fees or the hassle. Most exert their energy on finding a contractor who will fix the problem as soon as possible and get their solar system restored to full working condition. Hence, the true value of the workmanship warranty is contractor integrity and the likelihood of whether they both intend to and will remain in business to honor their contractual agreement. For most solar contractors, the standard ten-year commitment reflects a realistic forecast of longevity and commitment; avoiding the temptation to head off into fairytale land in order to beat-out the competition.
Eastern Shore MD,Solar Service, Home Solar Panels
Written by Lisa Walsh

Non-South facing solar panel installs in Maryland, DC and Virginia

The Design

Eastern Shore ,MD,Solar Service, Home Solar PanelsWhen planning a solar panel system for your home, the first consideration for any solar designer is the tilt and orientation of your roof areas.  We need to know which roof(s) will ensure the most optimum solar output – which translates to the best Return on Investment.   For us here in Maryland, the most optimum solar roof orientation is Due South at 180 degrees.  Of course, not everyone has this perfectly oriented roof and our customer base consists of homes that have South, West, East and everything-in-between orientations.  Occasionally we even install on North-facing roofs if the pitch of the roof is low enough that panels are close to flat, or can be tilted southerly.

For homes that face East-West, you may be wondering which roof would best suited for solar.  This is a good question given the fact that the output of your solar panels is directly related to your Return on Investment and how quickly the panels can pay for themselves.

If either East or West favors a more Southerly angle, then that would likely be a more favorable roof.  Assuming that there aren’t issues related to shadingor obstructions caused by chimneys, vents, skylights and other roof-placed items.

If the house has a perfectly split East-West orientation, with all things equal – the next consideration would be roof angle; the lower the tilt (i.e. closer to horizontal) – the more solar energy will be generated over the course of the day.  If the tilt on either side is the same then we would usually favor the West facing side.   Here in Maryland, DC and Virginia we tend to have cloudier mornings, and sunnier afternoons going into dusk.  Therefore we want to capture the late afternoon sun (west facing) more than early morning sun (East facing).  Of course, should you happen to have a tree, chimney or other obstructing factor(s) on the West roof – we’d favor the East.

The Economics

Homeowners looking at an East-West installation often have concerns as to whether or not their system will be profitable enough, compared to its south-facing counterparts.    Disqualifiers for cost-effective solar systems include shading and limited available roof space.  Rarely, however, is a home found unsuitable due to a Non-Southerly facing roof alone.

To illustrate, following is a comparison of a 10kW system’s output respective to East, West and South facing orientations.  Data compiled using the National Renewable Energy Laboratory (NREL) weather data patterns for Baltimore, MD –

10kW system installed on a 20 degree pitched roof with zero shade

 SOUTH (180 degrees)WEST (270 degrees)EAST (90 degrees)
ANNUAL OUTPUT13,224kWh11,389kWh11,328 kWh
*Annual $avings$1853 per year$1594 per year$1586

*Savings based on a conservative $3.00/watt installation, and $0.14/watt BGE rate

Data from PV WATTS

As illustrated, although perfectly South would be ideal, the East and West orientations provide a competitive amount of solar and would add only a few months to the payback period.  If you were choosing between East and West (as opposed to installing on both), the difference is nominal.  The choice of which roof may come down to aesthetic preference, distance to utility meter and regional weather patterns.

Written by Rick Peters

PACE Solar Financing in Maryland and Washington DC

Typical Commercial Challenges

As veterans of the small commercial solar market in this region, we are very familiar with the challenges of financing solar energy systems to this group of property owners.  Small businesses want solar as much or more than any other market segment, but they are capital-constrained like no others so they need affordable financing.

Third party solar developers have been the answer for other markets.  They can easily finance large systems because the cost of assessing the applicant’s credit is well worth the return.  In the case of residential systems, they can use universal tools like credit scores to help manage their risk.  For the small commercial and non-profit market, there hasn’t been a super-attractive  way to finance solar, until now!

Commercial Solar Systems Now Recognized as Public Benefit

Washington DC and Maryland now have laws and programs in place for commercial (and nonprofit) property owners to utilize PACE.  Property Assessed Clean Energy (PACE) is a vehicle that is used to finance energy improvements for buildings.  It operates under the recognition that energy improvements are considered to be a public benefit.  As such, PACE uses the property tax as a vehicle to structure the financing payments – much like we would finance a sewer extension, but in this case specific to one property.

PACE is very appealing to property owners because they can add significant value to their building on a cash-flow-positive basis without personal guarantees or the application of additional debt to the balance sheet.  The financing payment must be less than the savings and it’s paid in the form of a special assessment on the property tax bill over the term of the financing arrangement (5-25 years at competitive rates).  Multiple energy improvements (i.e. lighting, solar, new roof) can be bundled into one financing package.

The best thing about this approach to financing solar is that the property owner will own the system, not a third party.  The property owner gets all of the benefits, including the energy savings, the substantial incentives, the marketing value, and the satisfaction.  All it costs them is the interest on the financing which pales in comparison to the savings.

More info is available on your webpage on our PACE webpage but you may just want to pick up the phone and call us to see if your property is eligible.

Solar Service ,Home Solar Panels
Written by Lisa Walsh

DC Property Owners: Big Hot Water load = Big Solar Incentives

Commercial Solar Service, Annapolis MD

A growing number of building owners, developers and condo associations in the District of Columbia have come to realize that their building happens to be located in the most solar-friendly city in the USA .  Solar contractors, investors and financing vehicles are falling over each other to get solar panels on District roofs and start generating  the lucrative solar renewable energy credits (SRECs).   Whether via Direct Purchase, or $0 solar leases – SRECs are undoubtedly the reason for the solar season in DC (more to follow on those below).

However, before you sign on the dotted line and fill your roof with a 25-year solar PV (electric) system, as offered by 9 out of 10 solar professionals, make sure that you’re not losing the opportunity to vastly increase your return on investment with a Solar Thermal System.

Solar Water Heating Feasibility

The pre-qualification for a Solar Thermal System involves three questions:

  1. Does your building have a substantial, daily (365 day) hot water need? (i.e. apartment building/condos, restaurant, laundry, brewery, health center)
  2. Does your building have a centralized water heating system (as opposed to individual units throughout the building)?
  3. Can the building accommodate additional storage tanks?

If you answered YES to these three questions you really (really) should first consider a Solar Water Heating system either before – or at a minimum – in tandem with, a solar PV system.  (Shopper Beware – unless your solar contact has experience with solar thermal – which many do not – you’re going to have to be prepared to shop further).

What is Solar Water Heating (or Solar Thermal)?

Other than using the sun for energy generation, Solar Water Heating Systems operate entirely differently from their electron-shaking PV counterparts.  These time-tested, technologically mature systems are mechanical in nature and relatively simple.

Moreover, a solar thermal panel is 60 – 70% efficient; whereas a solar PV (electric) panel is typically 17 – 24% efficient.  Therefore, solar thermal panels generate substantially more energy per square foot than PV panels,  monetizing many more SRECs.

Solar Service , Home Solar Panels, Solar Renewable Energy

 

Let’s Review SRECs…

SRECs (Solar Renewable Energy Credits) – along with the 30% Federal Tax Credit and 100% Year 1 depreciation– are what drive the tremendous economic benefits of solar in Washington DC; one of several jurisdictions that have enacted a Renewable Portfolio Standard requiring that a specific percentage of electricity consumed must come from solar.   Whether residential, commercial, or institutional, each time a solar system generates 1 Megawatt hour of energy – the solar system owner generates 1 SREC.  This SREC is then sold via aggregators to an SREC market where it is bought by competitive energy suppliers to allow them to meet their share of the compliance obligation, or else pay a legislated fine (Alternative Compliance Payment, or ACP) for every SREC they are short.  Washington DC currently generates the highest SREC values in the country, largely due to the fact that DC does not have the real estate to install large solar farms which can rapidly oversupply a market and drive down SREC prices.

How much are SRECs Worth?

Washington DC SRECs are currently trading at $395/SREC.  To provide a frame of reference, a 6000 sq ft rooftop in Washington DC outfitted with a 75kW solar PV (electric) system could generate around 90 SRECs/year (over $35,000/year).   Depending on variables such as system size, corporate tax rate and and project site attributes, this SREC income – combined with a 30% Federal Tax Credit and 100% Year 1 depreciation, typically result in IRR’s between 30% – 60% and a Simple payback of 3 – 5 years.    Assuming solar thermal is applicable, this same roof outfitted with a Solar Thermal System could fit a kWh equivalent of a 150kW+ system, generating 180 SRECs/year – and see an IRR of 50 – 80%, with a simple payback in the 1 – 2 year range.

Solar Service ,Home Solar Panels, Residential Solar PanelsMaintenance

Although Solar PV (electric) clients often opt for an O & M (operations and maintenance) contract through their solar installer, Solar PV Systems  have relatively minor maintenance needs; usually an annual inspection along with ongoing monitoring.    Solar thermal (water heating) requires a little more maintenance including a 3 – 5 yearly service which, at a minimum, includes a replacement of the propylene glycol/energy transfer fluid that can degrade with time.  Nonetheless, the impact of service costs on the overall IRR is relatively small and easily absorbed by the increased SREC income.

Written by Lisa Walsh

A Primer on Solar Power

Did you know that attempts to harness the sun’s power through the development of solar cells dates back to the late 1800’s? I am sure that this, and other information, may be new to our readers. This article will provide you with some basic facts about solar power and solar energy. That way, you can join the conversation, and the renewable energy movement!

  • The first successful solar cell was developed in the early 1950s. It was made of silicon, and able to power small electronic devices. This was hailed as the beginning of a new era of energy resources, even then being acknowledged as having the potential to offer a limitless supply of electricity.
  • The first true application of solar cells could be found in the space program at NASA and in Russia. They were the only ones who could afford this technology in the 1960s.
  • The cost of solar cells continued to decline incrementally, but not so significantly that solar was a common source of energy through the 1970s. But, as the 1980s dawned, and ever since, solar power has insinuated itself into all aspects of life, commercially and residentially.
  • The first solar panels for buildings were developed in the early 1970s. In truth, this initial foray into the potential for large scale residential solar power was actually a solar array built into a rooftop. Panel development followed, as the cost and manufacturing efficiency increased.
  • President Jimmy Carter had solar panels placed on the roof of the White House in 1979. Everyone was getting into the act!
  • Welcome to 2018. Today it is common to find solar-powered cars, solar-powered telecommunications, and even solar-powered aircraft. One car company, renowned for their progressiveness, has incorporated solar panels into the roofs of their vehicles!

But, there’s more! Technology continues to expand the horizons of solar energy, making it affordable and applicable in new ways and new places. For example, it is possible that eventually solar panels on rooftops will be replaced with solar shingles!

Or, consider this, a solar fabric is being finalized that can be attached to houses as a cooling device!

We here at Solar Energy Services are excited about the future applications of this renewable source of energy for personal and commercial uses. You can count on us to utilize our superior knowledge and expertise to your advantage. We look forward to serving you!

Commercial Solar Energy ,Residential Solar Panels
Written by Lisa Walsh

Inverters: One Size Does NOT Fit All

Home Solar Panels ,Washington DC Solar,Commercial Solar Energy, Residential Solar PanelsIf you own or are planning to own your own solar power system, you’ve probably heard of an Inverter.    Although a vital part of any solar electric system, inverter choices can easily be overlooked in the shadow of seemingly more important decisions such as installer and solar panel options.   I mean, doesn’t an inverter just change the solar energy (DC) to house energy (AC)?  How complicated can it be?  Contrary to what your salesman or inverter manufacturers may have you believe, there is no “one size fits all” inverter.   As with many electronic devices; design, cost, warranty, time-testedness and monitoring capabilities are variables designed to offer as many choices as the different homes, businesses and climates they inhabit.  For example, you wouldn’t want to pay a premium for an inverter designed to deal with partial shading issues – if you have zero shading.  At a minimum, you’d at least appreciate knowing how the “other” inverter would affect the contract price.  So, in this spirit – let’s take a preliminary tour of the Inverter (or optional, microinverters).  Inverters have three primary functions:

  1. Inversion of the incoming DC energy (direct current) into home and appliance-friendly compatible AC energy (alternating current).  This is its main function.
  2. An MPPT (maximum power point tracking) function ensures that the inverter receives the maximum amount of power from the solar panel by adjusting the voltage (load) to match what the inverter wants; managing the complex relationship between sunlight and other varying conditions.
  3. Various electronic monitoring sensors that will, for example, detect when there is a fault in the grid-tied solar panel or on the grid and shut down power so the solar system cannot injure power-line workers during a grid outage.

The most traditional form of Inverter is a String Inverter, so-called because it is connected to a line or “string” of solar PV panels.  One solar power system, depending on the size/number of strings in the system, may have one or several string inverters which sit in parallel and convert the arriving DC current into an AC output.

Commercial Solar Energy, Residential Solar PanelsThese six string inverters service a large commercial solar electric (PV) system. Each inverter services forty solar panels, on four strings of 10 for a total of 240 panels.

Micro-inverters and Power Optimizers

Another type of inverter is the Micro-Inverter.  As the name suggests, this inverter is a smaller version of a string inverter, but rated to handle the output of each individual panel.  Therefore an inverter is located on the back of every solar panel unlike a string inverter that is often located on the side of the building/ground level.  Micro-inverters have been around almost as long as string inverters.  Historically, the manufacturing costs involved with making a dozen “mini” inverters couldn’t compare to the cost of one large string inverter.  However, as the solar industry has grown  – so has the demand for the micro-inverter; driving up demand while reducing production and distribution costs.

In response to the popularity of the micro inverter, Tigo, followed by String inverter giants SMA, developed a device called the Power Optimizer that works in conjunction with a string inverter.  As with micro-inverters, power optimizers are placed on the back of each panel and provide an MPPT function to each panel – limiting individual shading and orientation effects to the panel they’re attached to as opposed to the whole string.  However, because they are designed to operate alongside a string inverter they do not require individual transformers and are therefore much smaller, lighter and most importantly, cheaper than micro-inverters.

Solar design expert, Rich Schroeher says there is a time and a place for all three of these inverters:

Q:  Aren’t micro inverters better when the solar arrays are facing different directions or have different roof pitches?

Rich:  With micro-inverters, in essence, each solar panel is it’s own solar system, independent of the other panel/ inverter combinations, so various orientations of panels are easily accomodated.

With string inverters, a different inverter must be used for an array that is facing a different direction, or at a different pitch than the other arrays.

One way around this is string inverters that contain 2 MPPT inputs. These are, essentially, 2 inverters in one. They also have the added benefit of being able to handle more of the array than their rating. For example, let’s say you have two arrays facing different directions: one South facing and one East facing.  The entire system would use a 5000 watt inverter divided into two channels of 4000 watts for a total of 8000 watts.  The inverter will still only supply 5000 watts but when the south roof starts getting sun, the east roof is losing it. If at anytime more than 5000watts is being fed to the inverter, it just limits it to 5K.

 

Q:  Some homes have partial shading on the roof. How do you know when to use a string inverter – possibly with dual MPPT, or a power optimizer – or stick with a microinverters that will ensure a shaded panel won’t negatively affect the whole array’s output?

Rich:  It depends on the situation. Microinverters and optimizers can help with small areas of shading but are not a cure-all. They work best for an application where a small % of the roof is shaded at various times during the day, such as a chimney shading a few collectors where the shadow moves during the day.

Q:  Are there any longevity differences between string and micro inverters?

Rich: Opinions vary.  A solar system with 24 micro inverters, as opposed to 1 string inverter, has 23 more points of failure.  Plus the extreme temperatures that microinverters are subjected to can be an issue; electronics generally don’t like heat.  Microinverters are also located on the roof behind each panel, as opposed to the string inverter which is usually conveniently located close to the main electrical supply on the ground level.

Q:   Enphase microinverters claim to get greater efficiency, up to 16%, than their string counterparts due to the fact that the maximum power point is matched to the solar panel as opposed to the inverter, which limits the available output.

Rich:  In a Partial shading situation this could be true. If there is no shading at all or very early or late in the day when production is very low anyway it wouldn’t be near that high.

There are only two notable benefits that microinverters offer in a zero shade situation: they eliminate the string inverter losses from module mismatch (very small differences between modules), around 2 – 3%.  They also help with DC wiring losses.  Combined those two losses may be 5% overall.  This all assumes that the module attached is not too large (powerful) as to have any appreciable amount of clipping – meaning the full power of the module is limited by the inverter.

Q:  Microinverters, are more expensive than string inverters, at $.70/watt with a twenty-five year warranty.  Although String inverters are as much as 50% less, they often come with only a ten year warranty.  Doesn’t the microinverter’s longer warranty cover the inflated cost?

Rich:  In the long run probably no. Most string inverter companies’ offer extended warranties up to 20 years. Some include the cost of labor to replace. The labor cost to replace is about equal for a string inverter and a microinverter or perhaps a bit lower for string inverters depending on where in the array a failed micro is located. Say you have a system with 20 panels and the labor cost for inverter replacement is $150.00

      String inverter cost over lifetime $150.00

      Microinverter cost over lifetime  as much as $3,000.00 Plus 19 more scheduled trips and possible inconvenience to the owner. 

Q:  SMA’s new inverters include a “Secure Power Supply” capability.  What is this?

Rich:  This is a small (15amp) receptacle that is powered up when the grid goes down. As long as the sun is shining it will provide 120 volts of AC electricity. My first thought was to power a refrigerator or freezer to help carry a system owner through the outage without food spoiling.  It can’t be used at night but it will let you use some of the system during outages.

As is often the case, there are no cut and dry answers here. Variables such as system size, shading, orientation, panel layout and budget will determine whether a String, MPPT optimizer or micro-inverter may or may not be the best choice for your roof.  Most installers/designers worth their salt will consider all of these options and come up with the best solution for your house.

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