Residential Solar Panels, Solar Installer
Written by Lisa Walsh

Solar on Slate Roofs in Washington DC

Residential Solar Panels, Solar InstallerWith Washington DC offering homeowners the best solar incentives in the country – its small wonder that solar panels are going up like hotcakes. In order to meet the demand, most solar installers are adept at designing and efficiently installing solar panel systems on most roof types in DC: namely flat roofs and asphalt shingle. However, homeowners with a traditional slate roof will need to shop around for a qualified, slate-savvy installer.

Slate Roof Challenge

Washington DC Solar,Solar ServiceIn this order, the most common types of residential rooftops in Washington DC are flat, asphalt shingle and slate. Asphalt shingle are generally the simplest type of roof to attach to. They are flexible, soft and flashing/sealing all of the attachments has been fine-tuned to near perfection by the solar industry. Flat roofs are generally installed using no/few penetrations either with parapet-to-parapet rails or ballast-weighted systems. Slate, however, is among the most challenging roof type to work on for the following reasons:

  1. Expertise Tools and Labor Required

    Solar Service, Home Solar PanelsTraining a work crew adept at installing solar on a slate roof takes a significant investment of time, tools and techniques. As slate is a type of stone material – specialized diamond-tipped drills and copper replacement nails are required to penetrate and reattach the slate; drill too fast – and you’re likely to break the slate. Even with the most cautious of installers, a number of slates are still likely to end up broken and spares need to be kept on hand. Ideally – artificial slate can be used for replacing broken slates. Specialized flashings designed for use with the larger slate tiles must be used to seal around the attachment.

  2. Additional Labor

    Due to the fact that slate is essentially a smooth, slippery thin stone – this can be particularly challenging for installers to navigate. Couple this with a steep pitch, and extended hours on the roof due to time-consuming drilling techniques, labor estimates can easily double or triple when compared to an asphalt shingle roof; not to mention a particularly challenging and long day(s) for the installation crew.

The above two points ultimately result in increased costs for the customer. Fortunately, for DC residents with slate roofs, the financial incentives are such that paybacks are still generally under (or around) the 5 year mark – with many years of clear income to follow. Furthermore, as slate roofs can last 100 years or more, the roof and solar combination is set for a minimum 25 year relationship – and likely a good decade beyond that.

Solar panel, solar energy,Solar in Critical Areas Annapolis
Written by John Marrah III

Solar in Critical Areas – Maryland, Virginia and Delaware

Solar Panels, Solar Energy, Solar in Critical Areas AnnapolisWhat is the Critical Area?

The Critical Area includes all land within 1,000 feet of Maryland’s tidal waters and tidal wetlands. Along our precious shoreline of the Chesapeake Bay and its tributaries, we have had many homeowners looking to take advantage of enhancing their waterfront landscape with solar panels.

Aside from the clear economic advantages, we are in solar for all the right reasons; to protect the environment, preserve our natural resources, and to leave the world a better place. With that said, installing solar in the critical areas encourages us to comply with two important regulations that ensure shoreline preservation.

Lot Coverage

In the critical area, you are allotted a certain amount of lot coverage depending on the size of your lot. Our first step in the process is to prepare a “Lot Coverage Calculation” worksheet that indicates how much lot coverage you have available and ensures that there is legally enough space to account for the square footage of your new solar panels.

Buffer Management Plan

Though lot coverage is not impacted by solar installations outside of the critical area, the total area of additional lot coverage leads us to our next calculation. The Buffer Management Plan requires that every square foot of additional lot coverage is mitigated by planting either grasses, shrubs, or trees within 100 feet of the shoreline. The goal for this mitigation is to slow down the erosion of the shoreline, and we are big supporters of this mission. There is some flexibility with the types of flora that can be planted in this area, so we consult the homeowner in selecting preferred plants for their new shoreline oasis.

Though this process involves a few more steps in terms of permits, we have become subject matter experts thanks to our waterfront solar supporters in Kent County, Queen Anne’s County, Talbot County, Dorchester County and Anne Arundel County. Every county has a slightly different twist on their permitting requirements, and this helps local companies like SES thrive.

Home Solar Panel ,Solar Service
Written by Rick Peters

Peters’ Journey to Net Zero

Solar Service,Home Solar PanelsWhat Net Zero Meant for Us? Our Severna Park based, four-person family was looking to offset some of our home’s dirty energy, but we really did not have an expectation we could offset it all, but we had to start somewhere. We took our first step shortly after I joined the solar industry in 2008.

Low Hanging Fruit. In February 2009, we installed a 120-square foot solar water heating system to offset most of our water heating, and a small portion of our space heating for the first floor of our home. We saw big savings from this 3-panel system right away. Ever since, I enjoy the act of turning off the back-up water heating in April and leaving it off until almost October. For us, offsetting a dirty and expensive oil-fired boiler was the obvious low hanging fruit. We would later convert that remaining load to natural gas when the utility extended the pipeline to our home.

Solar Electric (PV) With the rest of the heat, A/C, and appliances all running off electric, it was time to look at the next opportunity. A few years later, when budget allowed, we decided to add a 5 kW solar PV system to our second story roof which faces SSE. My best determination was that we offset just over 40% of our electric load with that PV system. We were happy, but knew we’d want to find a way to get to NetZero eventually. , . I began to evaluate the remaining rooftops and consider what it would take to get us there. Solar panel efficiencies had improved a lot over the past several years so this reduced the remaining roof space we’d need to hit our goal

Phase 2 (PV). In the spring of 2016 we finished filling the balance of the south roof with some slightly higher wattage panels. As part of the same expansion, we added 24 relatively high efficiency panels to the E/W, low slope, rooftop of our one-story garage. We now had a total of 6.6 kW Equivalent of solar thermal and 13.8 kW of PV.

Not There Yet….We almost tripled our PV with the last upgrade and according to my calculations, this would get us to NetZero electricity. We’d know for sure by April, the annual true-up time frame for netmetering with BGE. When April 2017 came around, we were disappointed to come up a bit short (unfortunately, with a couple teenagers in the house, my usage predictions were a little off). Where do we go from here? I was not ready to put panels on the north roof, there had to be something available to us on the demand side.

Oops – More Low Hanging Fruit…One thing about Energy Efficiency, there’s always more opportunity. I had changed out many bulbs to LED over the prior several years, mostly through attrition, but I had not replaced any of the more than 2 dozen canister lights we had throughout the ceiling upstairs and down. Not only were these lights very inefficient, but the heat they generated in the summer was just adding to our air-conditioning load. We found the LED replacements on sale and replaced them all, as well as the remaining few incandescent lights in the house.

Commercial Solar Energy,Solar ServiceEureka. we have arrived!… In April of 2018 we received a $46 check from BGE for the annual overage from solar. With the kids heading off to college soon and a new refrigerator around the corner, I’m confident our checks from BGE will be getting bigger for the near future. At least until we purchase an electric car…

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.

solar energy, renewable,
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.

Commercial Solar Energy Residential Solar Panels
Written by Rick Peters

SRECs in Maryland and DC

What Does the Future Hold?

Commercial Solar Energy, Residential Solar PanelsSolar Renewable Energy Credits (SRECs) have played a large part in the financing of solar energy systems in Maryland since the RPS (Renewable Portfolio Standard) was enacted in 2005. These market-based, tradable credits are the property of the solar system owner to resell, typically to brokers who bundle them for final resale to competitive energy suppliers in the interest of meeting their solar compliance goals. In Maryland (as well as Washington DC), these credits are generated by both solar electric (PV) and solar water heating systems.

The price of SRECs is supposed to reflect the over or under supply of these credits in the marketplace. Both Maryland and DC have very aggressive solar goals (2% by 2020 in MD and 2.5% by 2023 in DC) with steep adoption curves so we need lots of SRECs to meet compliance.

Maryland:

That said, the solar industry boomed for several years recently and we are currently going into an oversupply phase in Maryland. This has the effect of pushing down prices on SRECs in the near term.   There are many contributors to the oversupply and the industry and legislators are frequently working hard to promote policies that help to smooth out the supply, but in the end, SRECs are a market mechanism that is subject to “animal spirits.”

As solar prices decline it is fitting that SREC prices are declining too – after all, we should need less incentives as solar costs come down to “grid parity.” When Maryland’s SREC market was conceived, the designers planned for a declining value as more solar got on to the grid. In fact, the Alternative Compliance Payment (ACP) schedule – the amount energy suppliers have to pay if they cannot buy SRECs – is designed to decrease over time. The ACP is considered to be the maximum that an SREC would cost in a rational market. Recently SRECs have traded on the order of 35% of the ACP, but as high as 75% a few years ago. In Maryland, the ACP is scheduled to drop from $400 to $350 in 2015 and then down to $200 in 2017, $150 in 2019, and so on.

DC

Washington DC is a different market and one that is much better insulated from the shocks of large utility scale systems that flood SRECs onto the market. The sheer geography in DC does not lend itself to 10 MW solar farms and thus the SREC supply curve is a little smoother due to the requirement being fulfilled primarily with many smaller systems. As a result, DC SRECs have shown more consistency and maintained a higher price, benefitting system owners and prospective system owners.

What now?

Regardless of the trends for solar return on investment (ROI), we all want to maximize our incentives for our own benefit. SRECs are no different. While there are many more new solar customers every day, there are also many solar system owners now approaching the end of 3 or 5 year SREC contracts (aka “strips”) and they too need to decide how to proceed going forward. Do I want to sign up for another strip (3 or 5 year term contract) and accept a large discount on my SREC price for that price security or do I want to maybe float with the market for a while? I’ve got no crystal ball, but I do know that there are many efforts underway in Maryland, some legislative and some not, to help to smooth the SREC supply and thus maintain a reasonable value for SRECs to continue to help incentivize solar. For that reason, I believe we will see some recovery of SREC prices in Maryland in the next year or two and thus maybe it is better to hold off on a term contract. In DC, I would personally opt for more surety and take a term contract with the discount price, but that is my risk averse nature. Others might like to bear more risk and float in hopes of higher SREC values in the future.

Either way, we are lucky to have these incentives in Maryland and DC. They are working to increase solar installations and jobs and they are also helping to drive down the installed price of solar in our region.

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