Solar Power for Homes: How Does a Solar Panel System Work in 2021?

How Do Solar Panels Work?

how a solar power system works
How a home solar panel system works in 4 steps
  1. Solar cells convert photons to electricity: All photovoltaic solar power systems like the traditional solar panels, BiPV solar shingles and tiles, and thin-film solar laminates contain photovoltaic solar cells designed to convert solar energy to electricity. When the sun shines, the energy carried by the photons gets absorbed by the solar cells that convert it to direct current (DC) electricity.
  2. Inverter converts direct (DC) current to alternating current (AC): All rooftop solar panel systems are normally connected to an inverter by a licensed electrician during the installation. The inverter inverts (converts) the direct current (DC) electricity generated by the solar cells to alternating current (AC), which is the kind of electricity people use in their homes.
  3. Alternating current flows through the electric panel into your home: Alternating current from the inverter flows through the electric panel (circuit breaker box) into your home, powering things like home lighting and appliances.
  4. Any unused electricity gets sent back to the electric grid: Any excess electricity that is not used domestically, passes through the electric meter and gets sent back to the grid, usually for electricity credits via net metering.

Net Metering: If you live in one of the 41 states that have adopted Net Metering rules, you can sell any excess solar-generated electricity back to the local electric grid for credits.

Did you know? Many local electric utilities are often required by local net metering rules to “buy” your excess electricity at pre-set rates (usually at the same rate that residential customers pay for electricity) for credits.

You can also qualify for the 26% federal tax rebate at the end of the year for the installation of a PV solar power system. Be sure to also check your state and local utility incentives, and talk to your tax accountant about claiming the federal solar tax credit rebate when you file your taxes.

Tip: Learn more about the Pros and Cons of Solar Energy here.

Solar power systems use photovoltaic cells to generate clean, renewable electricity from the abundant solar rays, harnessing the energy of the sun. — Currently, there are three main types of PV solar systems available to homeowners: solar panels, solar shingles, and thin-film laminates. Let’s explore.

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PV Solar Panels

PV panels are the most common and recognizable type of solar power systems installed on the residential rooftops today by companies like SunPower, SunRun, and Tesla Solar.
Fun fact: In the northern hemisphere, PV solar panels normally get installed on the south-facing side of the roof for optimum exposure to the sun.

Monocrystalline vs. Polycrystalline Solar Panels for Homes

PV Panels are based on solar cells made from silicone and placed inside a panel designed to contain many individual solar cells.

Monocrystalline PV panels are more energy efficient (15% to 23% efficiency) and cost significantly more than polycrystalline panels.

High-efficiency and highest quality monocrystalline solar panels from companies like LG, Panasonic, and SunPower, will typically boast 20% to 23% efficiency ratings and a 90% efficiency promise at the 25-year mark.

Did you know? Most residential-grade high-efficiency PV panels are rated for 300 to 400 watts, and cost between $250 and $550 per panel, depending on the manufacturer.

Polycrystalline solar panels are less efficient (13% to 17% on average), typically range between 200 and 300 watts, costing between $150 and $200 per panel, depending on the specific model of the panel and its manufacturer.

How Many Panels Do I Need?

When going with midrange monocrystalline panels rated for 250 watts, you will typically need 24 panels for a typical 6kW home solar system.

If your roof has limited span or you simply want to opt for more premium high-efficiency panels like LG Neon R 360W (delivering 90% efficiency after 25 years) that are rated for 360 watts, then you will only need 17 panels for a 6kW PV system.

Solar ROI is known as the Pay-Back or Break-Even Period:

The ROI for a PV solar power system can be very significant and net-positive, with a short pay-back period, provided your roof surface has sufficient space and exposure.

Most PV solar panel systems pay for themselves in 8 to 10 years.

PV Solar Panels System Components, Costs, and Tax Credits:

Today, most solar installations consist of PV solar panels, an inverter, and a connection to your electric meter or electric grid. At an average cost of about $2.96 per watt installed, a 6kW solar panel system will cost approximately $18,000 before the 26% federal solar investment tax credits (ITC) that are in effect through the end of 2022, after recently being extended by congress.

These ITC credits will be reduced to 22% in 2023, which is the final year to take advantage of the federal ITC credits for installing a PV solar power system.

Solar leasing options are also available, but you must be careful about the terms and the actual cost per watt based on the entire system. The larger the system, the smaller your cost per watt should be.

Roof Slope Concerns?

Installation of PV Solar Panel arrays on a flat roof covered with a 50-mil PVC membrane

Can solar panels be mounted on any style of the roofing surface including low-slope roofs?

The answer is a resounding yes, as long as the roof surface itself does not have any intervening protrusions or obstacles like chimneys, dormers, or skylights.

However, the roof frame needs to be strong enough to support the weight of the roof covering, plus the weight of solar modules. The roofing system protecting the house must be designed and engineered to last 25+ years to match the typical lifespan of modern solar panels.

Large Solar Panel Installers: What You Need to Know

Tesla Solar, formerly SolarCity, which was acquired by Tesla in 2016 to stave off the looming bankruptcy of SolarCity in which Elon Musk, his cousins, and his companies like SpaceX were heavily invested.

At the time, SolarCity was one of the most well-known solar providers and had the greatest market share. It was also one of the priciest vendors (on a per solar watt installed basis) known for aggressive sales tactics of all the solar power providers. — Interestingly, SolarCity prices per installed watt had little to do with the quality of the product or service, but rather it was the result of the aggressive approach to sales — knocking on doors and using high-pressure sales tactics to get you to sign the contract..

Did you know? SolarCity was on the verge of bankruptcy when it was acquired by Tesla and has shrunk in size quite a bit since the acquisition took place.

Other large residential solar players in the space include SunGevity (now merged with Horizon Solar Power), SunPower, Vivint Solar (acquired by SunRun), SunPower (which recently split into two companies manufacturing and distribution, and sales and installation service), and many other regional and local solar installers.

The largest installers typically don’t offer the best deals on solar

According to EnergySage and the NERL report findings (PDF) by the U.S. Department of Energy’s National Renewable Energy Laboratory, homeowners who get multiple quotes, save an average of 10% on solar installations compared to homeowners who only get a single quote from a large installer.

A recent report by the U.S. government found that large solar installers with regional or national presence are $2,000 to $5,000 more expensive than small solar companies. If you have offers from some of the larger solar installers like SunRun, make sure you compare those estimates with quotes from local solar installers to ensure you don’t overpay for solar.

In addition to comparing the quotes strictly on the “bottom-line basis”, also consider the quality of equipment you will be getting, product and workmanship warranties, and experience of the crew.

Pro Tip: If you are looking to compares solar quotes from local solar companies, EnergySage (no affiliation) is the Amazon of solar marketplaces where homeowners can get free quotes from local installers. They also make it easy to compare verified solar company reviews, and have an easy to use solar savings calculator for estimating your home solar system’s payback period.

What about BiPV Solar Shingles and Tiles like SunTegra, CertainTeed Apollo, and Tesla Solar Roof?

Building-Integrated PV solar shingles are designed to integrate seamlessly with the roof! Unlike the traditional solar panels, BiPV solar roof shingles don’t need to be bolted onto the roof, because they are part of the roof itself!

BiPV solar shingles are not currently widespread, at least not yet due to a significantly higher cost per installed watt vs. PV panels.

Thus, your total cost per kilowatt of electricity generated will be higher with solar shingles compared to traditional bolt-on PV solar panels. — That is the main reason why Dow’s chemical PowerHouse Solar shingles manufacturing and sales division had ultimately closed its doors and ceased the sales of their products.

Did you know?

At present, there is another BiPV solar shingles alternative called Appolo Tile 2 available from CertainTeed.

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PV Solar Panels on Metal Roof

Thin-film PV Solar Laminates

Thin-film photovoltaics are designed specifically for energy-efficient and long-lasting standing seam metal roofs.

Installation: Thin-film laminates are designed to stick onto the 16-inch-wide standing seam metal panels — By removing the peel and sticking the laminates coated in adhesive onto the metal panel in between the seams.

Thin-film laminates come in rolls available in several different sizes designed to work with a few common widths of the standing seam metal panels. On a per square foot basis, thin-film solar laminates are less-costly than the conventional PV solar panels. The ease of installation, which does not require any penetrations made to the roof surface, is their main selling point.

However, thin-film laminates are less-efficient than the traditional crystalline solar panels, as they don’t have the same energy production density as their bulkier counterparts. — That is yet another reason why they are currently hard to find and buy.

Thin-Film Solar Laminates Require Standing Seam Panels

To really get the benefit from this innovative product, you would need to replace your current roof with standing seam, first. Provided your roof has sufficient exposure to the sun, you can get a “panel free” solar roofing system designed to last for many decades.

If you are intrigued by the idea of the thin-film photovoltaics and would like to learn more about the current solar laminate options available for metal roofs, then you need to know that Uni-Solar, the biggest residential thin-film PV solar laminates manufacturer in the US, has closed its doors in 2012 because it could not compete with traditional crystalline PV solar panels on price, largely due to the falling prices of crystalline solar modules.

You can still buy Uni-Solar Thin Film Laminates, but there are now some Commercial Solar Laminate options, which gives us a sense of hope!

Today, there are still some small companies selling Uni-solar laminate rolls on Amazon, but the product is no longer being manufactured.

However, not all is so grim in the thin film PV solar laminate products market. In fact, there is a company called SoloPower providing thin-film laminates optimized for the sixteen-inch-wide standing-seam metal roofing panels integration.

SoloPower are currently in business of serving commercial, government, and municipal roofing clients, only. They don’t currently offer any residential solar laminates.

Important Update: Fabral (OmniMax) in partnership with MiaSole offers Flex 02NS (PDF) – Thin-Film PV Solar Laminates (MiaSole) (Factory pre-installed) combined with Standing Seam metal roofing panels suitable for residential installations.

You can always go with a standing seam metal roof, but instead of getting the thin-film solar laminates attached to your metal roof, you can also opt for a bracket-mounted traditional PV panels system attached by means of special metal clamps to the raised seams of a metal roof.

Consider investing in high-efficiency panels from a proven manufacturer like SunPower (most premium), LG, and Panasonic known for high efficiency and longevity of their residential solar panels.

As far as longevity and watertightness of the roof is concerned, the use of special brackets designed specifically for standing seam panels means that you will not have to poke any holes in your expensive metal roof! 🙂

Standing Seam Roof integrated with PV Solar Panels

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