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 Service ,Home Solar Panels
Written by Lisa Walsh

Poly Vs Mono Panels for Residential Solar Installations

IfSolar Service, Home Solar Panels,Commercial Solar Service ,Annapolis MD – like most educated consumers – you’re getting multiple quotes for your solar power installation, you’re probably having to compare between various equipment offerings by your solar vendors. Themostprominent of these offerings – both in terms of financial investment and warranty security –are the solar panels themselves.

Solar panels come in a variety of power ratings. For residential applications, the most popular panels today usually fall somewhere between 270 watts and 315 watts, with price points that usually increase with the wattage (in the standard size footprint). Less obvious, however, is the type of solar panel you may be asked to choose between.

In general, your solar quote will include a panel whose cells are made from crystalline silicon. Silicon is us

ed in solar panels not necessarily because it’s the most optimum semi-conductor available – but because of the extensive research on the processing and physics of silicon grown out of the integrated circuit industry. The processes used to access and arrange the silicon determine whether a panel is deemed to be

As the name suggests, monocrystalline panels utilize a single, continuous crystal structure in the processing of the silicon ingots from which the solar cells are made. It used to be that this high-grade silicon resulted in substantially higher efficiency rates than other solar panels. However, improvements to manufacturing in polysilicon processes have closed this gap significantly. Still, homes and businesses looking for the highest possible efficiency rating on a solar panel would likely choose a Mono panel.

The silicon ingots used for manufacturing the solar cells for Poly panels are manufactured by melting many fragments of silicon together to form the ingot. Because this results in many crystals in each cell, there is usually less freedom for the electrons to move. As a result, polycrystalline solar panels typically have lower efficiency ratings than monocrystalline panels.

Should I choose a Mono or Poly solar panel?

As with any choice it comes down to buyer preference:

Aesthetics: In general, Mono panels have more options if you are concerned with how your solar panels will look. If you want something low-profile; maybe a uniform, all-black aesthetic devoid of white lines, silver racking and diamonds – most manufacturers offer this aesthetic in a Mono panel. However, there are now a few poly panels available in all-black. For example, REC has a 280-watt poly panel on the market that is now available in all-black.

Cost:  Mono panels tend to cost more than poly panels. A small roof looking to get the highest possible solar fraction by going with a high wattage solar panel will most likely end up with a Mono panel as these include the highest wattage options (300w plus). However, if a homeowner has the roof space and is looking for the highest possible value, it may be most cost-effective expand the array by one or two more panels and go with a Poly. Many commercial applications utilize poly panels due to the focus on cost over aesthetics, particularly if the panels are not visible from the ground, due to a flat roof installation.

Performance:  Due to the amount of information out there disparaging efficacy of poly panels compared to monos, this is a subject worth broaching. It is true that under factory test conditions, poly solar panels tend to have slightly lower heat tolerance than monocrystalline solar panels. As a result, under high temperatures, poly panels would perform slightly worse than their mono counterparts. Heat can affect the production performance of solar panels and shorten their lifespans. However, this effect is minor, and most homeowners do not need to take it into account. This is evidenced by the standard 25 year manufacturer’s warranty is the same for both mono and poly panels.