Solar Panels for Home
So you understand the great benefits of solar – but how does the technology actually work? Check out this next section of our starter guide and these videos to find out.
How Home Solar Works:
- Your solar panels convert sunlight to DC electricity.
- Your inverter converts DC electricity to AC.
- Electricity is used to power your home.
- Extra electricity is sent to the utility grid for a credit, or to your battery if you have one.
From our blog:
- How Do Solar Panels Produce Electricity?
- Will Solar Panels Keep Working If The Power Goes Out?
- Do Solar Panels Work At Night?
What are the key aspects of solar for my home?
The basics of home solar are pretty simple. There’s just a few things you need to be familiar with to understand how to set up a proper system.
Net Energy Metering and Solar
Net Energy Metering (NEM) is the policy that allows you to push and pull energy to and from the grid through your electrical meter. Traditional utility users pull energy from the main grid, use the energy in their home, and the meter counts how much is used. With solar, you will push your excess energy into the grid during the day and pull it out at night to use for lights, TV, A/Cm or anything else you may need.
Grid Tied Solar
After you go solar, you will still be connected to the grid. This is so you can take advantage of NEM to maximize the value of your system. Essentially the grid functions as a bank storing your energy from your solar panels until you are ready to use it. With a battery backup system and secure power supply, you can use the energy from your system when the grid goes down.
Net Energy Metering Credits
If you don’t use all the energy your system produces in a day, that energy will roll over to the next day and so on. This happens day after day, month after month. This allows you to use all the energy you produce with your solar system. If you have higher usage months (AC, guests, holidays, etc) you draw from the extra energy credits you earned earlier in the year.
Once a year you “true up” with your utility where you settle the balance on your energy credit. If you consume more than you produce then you’ll pay the utility for the excess energy you pulled from the grid. If you produce more energy than you consume, the utility will compensate you for your excess energy at a below-retail rate.
From our blog:
What are the key pieces of equipment for a solar panel system?
Here are the most important equipment components to the standard solar panel system for your home.
Solar panels are modular pieces, usually rectangular in shape – approximately 3’ by 5’ long. They vary in size, electrical output (measured in Watts), efficiency, and even color (most solar panels have either a black or silver metallic frame, and the cells will usually appear a dark blue or black in the light.) Panels can be mounted to a home or building’s roof structure, or installed on a ground-mount racking structure. The panels contain silicon cells that when exposed to sunlight, create a flow of direct current electricity or DC. Check out our full-length guide on how to find the best solar panels for your home.
Keep in mind: When thinking about where to locate solar panels for a home, it’s important to consider factors that will affect the system’s energy production (measured in kWh). In the Northern Hemisphere, facing south is typically ideal.
From our blog:
- How Long Do Solar Panels Last? A Detailed Review
- 4 Factors That Can Affect Solar Panel Production
- Monocrystalline Solar Panels vs Polycrystalline Solar Panels
The inverter is the device that converts (inverts, technically) the direct current electricity produced by the solar array(s) into usable alternating current, or AC electricity. There are several different types of inverters a solar installation might employ. String inverters are the simplest, most mature inverter technology, in which the DC from groups of solar panels linked in series are fed into the inverter. The inverter puts out AC electricity which is then fed to the home’s electrical infrastructure. Micro-inverters are small, modular inverters that are furnished behind each solar panel in an array (1:1) and effectively compartmentalize the AC energy production of each panel so that the reduced production of one panel does not affect the output of the entire system.
Keep in mind: Some inverter companies such as SolarEdge offer power optimizers, which essentially act like micro-inverters on a string-array.
From our blog:
Solar Monitoring System
It’s important that every residential solar system has a monitoring system. This is the system that will allow you to view and measure real-time and historical energy production data of your system. Some monitoring systems display this energy production data via a physical display unit, while others employ an online interface, or both! As “smart” or connected homes become more prevalent, solar installers can provide whole-house energy consumption monitoring as well. In order to ensure your solar system is producing energy normally, it’s important to make sure your solar panels are paired with an energy production monitoring system.
Keep in mind: Solar.com will audit your monitoring system FREE of charge to ensure your solar array is producing what it should.
Solar Mounting and Racking System
A racking system is the structure on which your solar panels will be mounted to your home’s roof structure or on to the ground. While some racking systems may vary in their look, they exhibit similarities in their form and function. It’s important to make sure your racking system, if roof-mounted, is properly flashed and sealed to ensure your roof is well-protected against the elements. Roof racking systems vary slightly depending on the type of roof.
Keep in mind: On flat roofs, a ballasted racking system can be used which requires no roof penetrations.
From our blog:
What are the important aspects of planning my solar project?
Now that you understand the key factors for solar pricing and equipment, it’s time to share the important aspects to planning your solar project. This includes choosing the right installation company; reviewing the solar contract and warranties; understanding the process of solar installation; and making sure you properly maintain your system once it is fully installed.
Solar Installation Company
When considering your installation company, it is important to know their number of installations, their locations, their bankability, their online reviews , and most importantly, our internal rankings. You will also want to strongly consider the length of their workmanship warranty. Workmanship warranties cover roofing penetrations, water damage, electrical work, and anything related to their installation for the time period described. You’ll also want to get references and testimonials from their past customers. Pick My Solar provides information for every installer in our network.
From our blog:
Solar Installation Contract
Contracts can often be overwhelming and packed with a lot of legalese. There are a few key areas of the contract that you should confirm are accurate: progress payments (how much you pay and when); any additional line items (service upgrades, EV chargers, buried lines); escalator rate (for lease or PPA); detailed warranty information; cancellation clause; system’s first year production estimate; and hardware specifications.
From our blog:
- What to Expect from a Solar Contract
- What To Ask A Solar Installer Before Signing On The Dotted Line
A professional, licensed solar installation company will provide an installation or workmanship warranty in addition to the warranties provided by the equipment they install (panels, inverter(s), optimizers, monitoring, racking system, etc). As for the equipment, most solar panels come with a performance warranty lasting 25 years. The performance warranty guarantees that a panel’s output capacity will not drop by more than 0.7% per year, or less than 20% over 25 years. This means that your system is warrantied to be at least 80% as productive 25 years after it is installed. This degradation rate can range from about 0.4% per year for modules from companies like SunPower, to about 0.9% per year for others, but 0.7% per year is the industry standard.
From our blog:
Solar Installation Process
The actual installation of a solar PV system typically takes only a day or two. First, the materials are brought to your house as the crew of 3-5 workers arrive. Next, standoffs are installed on the roof, then flashings. Rails are then installed and the solar panels are attached to the rails, conduit is run for the wiring, and the system is then tied-into the main service panel. City inspection is then scheduled by your solar installer. After your city approves the system, the installation company then applies for permission to operate from the utility, which can take 1 – 4 weeks depending on the utility and volume of applications. The installation company will then switch on the PV system, set-up the monitoring system, and then you are good to go!
From our blog:
Solar Panel Maintenance
Solar PV systems require almost zero maintenance. The rain should be sufficient to clear off the dust and dirt on your panels, but you could do no harm by hosing of your panels every 2-3 months at the most. In areas that receive snowfall, snow shouldn’t be a major problem. Panels will still receive sunlight through the snow and heat up, causing the snow to slide right off.
When purchasing a solar system, maintenance is on the homeowner. Your workmanship warranty will cover labor to service or replace any hardware if it cannot be fixed remotely. If you lease a system or do a PPA, the financiers will almost always offer a ‘maintenance package’ where they offer to clean the system biannually or annually. Studies have shown that this is unnecessary for most tilted arrays. Be wary of these ‘maintenance packages’ as they are often overpriced.
From our blog:
Key Solar Panel System Terms
- AC – Alternating Current – This refers to the current of an electrical device. AC is what U.S. households are accustomed to. All appliances, lights and other home electrical devices run off AC. Our power lines carry AC as well. However, when solar panels create energy, they create it in DC, creating a need for an inverter to convert the energy to AC.
- Angle of Incidence – The angle a ray of sun makes with a line perpendicular to a solar panel. For example, if a panel had a 0-degree angle of incidence, it would be directly above the panel. At sunrise or sunset, it would be close to 90 degrees. The closer to 0 degrees, the more direct the sunlight, and thus the more energy a panel would produce.
- Carbon Dioxide (CO2) – This is produced from fossil fuels when they are burned to produce electricity. Carbon is commonly known as the greenhouse gas that is most severely affecting global climate change. With solar energy, your personal carbon production will be far less than continuing to use power from the utility grid.
- Community Solar – This is when there is a shared solar system that multiple members of a community invest in. When a utility customer cannot put solar on their own residence, they may opt into community solar. How community solar works with utility systems is still being figured out in some areas, but in other areas, community solar is up and running. By opting into a community solar program, it will likely save the members money on electric bills and offset carbon use for the community.
- Current – A flow of an electrical charge carried through wires. Read more under AC and DC.
- DC – Direct Current – This refers to the current of an electrical device. DC, or Direct Current, is produced by solar panels and batteries. DC can be converted to AC through an inverter, which is how we’re able to use the electricity produced from solar panels in our houses. When we refer to the size (watts or kW) of solar, we’re referencing DC output. Once the conversion to AC has been made, the AC watts will typically be 15%-20% less than the rated DC watts.
- Diffuse Insolation – This refers to sunlight received indirectly due to clouds, haze, fog, or other atmospheric obstructions. This sunlight will not produce as much energy as direct insolation, but it can still produce energy. Monocrystalline cells are best suited to maximize production from diffuse insolation.
- Diode – This allows electricity to pass in one direction but not the other. This is used on a solar system to ensure energy is not sent back to panels when they are not producing electricity.
- Direct Insolation – This is how much direct sunlight hits an area of Earth. This is determined by taking the irradiance above the atmosphere and subtracting atmospheric losses.
- Electric Current – This is the flow of an electric charge. This charge is created by electrons flowing through a wire.
- Energy Audit – These are performed on buildings to analyze the energy input into them. They are done both at the time of construction to pass municipal mandates and at a time when the building owner is looking to conserve energy. Homeowners often do this to better understand how much energy they use and what upgrades they would be able to do to use less energy and save money.
- Fossil Fuels – Coal, oil, and natural gas are the three major forms of fossil fuels we use today to create energy. These are natural resources that formed over millions of years. When these are burned to create power, they put off extensive amounts of pollutants into our atmosphere, which has been proven to be a root cause of climate change. Solar energy is produced directly from the sun without having to burn fossil fuels, therefore combating global warming.
- Full Sun – The amount of sunlight hitting a surface at midday. This signifies the maximum output of a system.
- Ground or Grounding – A ground is where the voltage is zero. Grounding is something done to all solar systems by attaching any metal features of a solar system to a ground. This protects against unintentional shocks or potential fires by “grounding” the voltage. Basically, it removes any potential voltage from areas where it is not intended to be.
- GW or Gigawatt – A unit of power equal to 1 billion watts, 1 million kilowatts, or 1 thousand megawatts.
- Incident Light – Sunlight that shines on the surface of a solar module.
- Insolation – Solar power density on a surface over a period of time. This measurement is in Watts per square meter.
- Irradiance – The total solar radiation that strikes a surface, including direct, diffuse, and reflected radiation. Irradiance multiplied by time equals insolation.
- Jurisdiction – The legal body authorized to administrate justice. These are at the state and national level, but also local townships or city levels. Your local jurisdiction will dictate construction permitting for solar. Solar permitting laws vary per jurisdiction.
- kW or Kilowatt – A unit of power equal to 1,000 watts.
- kWh or kilowatt-hour – A measure of energy equal to 1,000 watts consumed over 1 hour.
- Latitude – This specifies the north-south position on Earth’s surface. The latitude at the Equator is 0 degrees while at the North Pole it’s 90 degrees. The greater the latitude, the less sunlight the surface of the Earth will receive each year. Therefore, solar systems further south will produce more energy that systems further north, barring all other variables. Your latitude will also dictate the ideal tilt of your solar panels. The further north you are, the greater the ideal tilt.
- Longitude – This specifies a location on Earth east or west of Greenwich, England. Your longitude won’t have an effect on your solar production and is commonly mistaken with Latitude. Your longitude will dictate the time of solar noon.
- MW or Megawatt – A unit of power equal to 1 million watts or 1,000 kilowatts.
- Municipality – A city or town with a local government.
- Net Metering, Net Energy Metering, or NEM – A system where individual solar systems are connected to the public utility grid. Solar systems may send energy back onto the grid, get credits for the energy, and then use those credits at a later time – the individual is therefore only charged for the “net” usage.
- Open Circuit Voltage or Voc – The highest voltage that can be produced by a solar panel or system – this occurs when the current is zero (no load connected). As the temperature of solar equipment decreases, this value will increase. The value of the Voc must be less than the maximum input voltage of the inverter.
- Parallel Circuit – An electrical circuit with two or more paths. Micro-inverters create a parallel circuit for a solar system and protects against a single panel not performing optimally. A string inverter will create a series circuit.
- Passive solar home – This is a home designed to have all of its components, including walls, windows, and floors, to collect solar energy in the winter and reject solar energy in the summer. Therefore, it “passively” cools and heats a home using the energy from the sun.
- Photons – Particles that are carried through sun rays and essentially produce solar energy.
- Photovoltaic or PV – The process of photons exciting electrons – this creates electricity. A PV system, photovoltaic system, and solar system are all interchangeable terms.
- Power/Conversion Efficiency – The amount of sunlight converted into electricity. The rest of the energy is lost to factors such as reflected light and heat. The efficiency of a solar panel will determine how much a panel can produce per square area.
- Renewable Energy – Any form of energy which replenishes from the sun. This includes solar, wind, geothermal, bio, tides, etc. The sun is the ultimate factor replenishing all of these sources. Since they are renewable, the amount of carbon produced from these sources is little or none.
- Series Circuit – An electrical circuit with only one path. A clear depiction of this can be seen in typical Christmas lights. When one light goes out in the string, the entire strand goes out. This is a series circuit. If when one light went out, the rest could remain on, this would be a parallel circuit. Series circuits are found in central or string inverters in a solar system – the strings are in series.
- Silicon – This is a material found in solar cells and creates the chemical phenomenon known as the photovoltaic effect. Silicon is the base material in all PV cells.
- Solar Cell or PV Cell – This converts sunlight into electricity. Every solar panel is made up of multiple solar cells. The typical solar panel has either 60 or 72 solar cells. These cells are either monocrystalline or polycrystalline cells.
- Solar Noon – The point of time during the day that the sun is at its highest point in the sky. The time of solar noon is dependent on the longitude of a location.
- Solar Photovoltaics or Solar Cells – Turn sunlight into electricity through the photovoltaic effect.
- Solar Power Plant – Much like a coal, nuclear, or natural gas power plant, but entirely powered by sunlight. A solar power plant can be composed of either solar photovoltaics or through heating steam through a combustion engine. Every home that puts solar on their roof creates their own solar power plant.
- Solar Radiation – Radiant energy emitted by the sun. This includes all spectrums of radiation from visible light to ultraviolet rays – including the rays that burn your skin.
- Solar Spectrum – This includes all the electromagnetic waves that come from the sun. The wavelength dictates the type of energy and whether it is visible light or ultraviolet rays.
- Solar Thermal – Technology that uses the sun’s rays to heat fluids. Solar thermal first caught on in the 1970s as a residential alternative to heating water in homes. Since then it has expanded to heat pools as well. Larger scale solar thermal power plants heat fluids to create steam to run a turbine.
- Transformer – This is an electrical device used to increase or decrease voltages in appliances, power lines, and other electrical applications.
- True South – This is the direction of directly south in correlation to the sun. This is typically different from magnetic south. To determine true south, you’ll need to figure out when the sun is directly overhead – that is true south. Solar systems are best oriented to true south.
- Utility – When relating to solar, we speak of Utilities as the source that delivers you electricity. Your utility might also deliver water and natural gas. Your Utility maintains your power lines, balances the grid’s load, and generates or procures electricity.
- VAC – This pertains to the AC voltage. U.S. homes have sockets that are between 110 and 120 VAC.
- VDC – This pertains to the DC voltage. Most batteries run at 12 VDC.
- VMP or Voltage Maximum Power – This refers to the voltage of a solar panel at maximum output current with ideal conditions.
- Voc – Another term for open circuit voltage.
- Voltage – This is the electric potential between two points, measured in volts.
- Volts – A unit of electrical force that will cause one a current of one amp to move through a resistance of one ohm.
- Watt or W – The rate of energy transfer with respect to time. One joule per second is equal to one watt. For example, a typical light bulb is 40 to 60 watts.
- Watt-hour or Wh – The equivalent to one watt of power used over a period of one hour. A 40 watt light bulb used for one hour would use 40 Wh.
- Zero Net Energy – This refers to a building that produces the same amount of renewable energy that it consumes.
Solar Panel Specification Terms
- American Manufacturer – A company whose materials are manufactured in America.
- Anti-Reflection – Coating applied to the glass of solar panels in order to reduce sunlight reflection and increase the efficiency of the panel.
- Back Plate – The outermost layer of the module that protects the internal parts of the cell from outside harm and insulates the cell.
- Building Integrated Photovoltaics (BIPV) – Building integrated photovoltaics function both as an external layer of a building and as an energy producing system. Examples of BIPV include solar shingles and solar windows.
- Black-on-Black – All black solar panels consisting of a black frame, black cells, and a black backsheet (film substrate on which the cells sit on). This is done for an aesthetic appeal.
- Degradation – Gradual reduction of panel power output over time due to corrosion from water vapor, metal ion migration, deterioration of the anti-reflection coating, temperature, UV exposure, and mechanical damage
- Frame – Encases backsheet, solar cells, and glass on solar panel.
- Monocrystalline – Composed of a single layer of crystalline silicon cells, which allow electrons to move freely around cell and results in slightly more efficient panels. Monocrystalline panels have oval shaped cells and are usually black.
- Multicrystalline – Formed by melting multiple layers of crystalline silicon. These are typically cheaper and less efficient than monocrystalline panels.
- Nameplate Rating – Indicates the power output of a solar panel under industry standard test conditions. Higher nameplate ratings mean a higher power output from the panel. Ratings typically range between 200 to 360 watts.
- Nominal Power – Maximum DC power output of a solar panel under industry standard testing conditions. This is different than the power output under real world conditions, where there are typically losses due to various factors.
- Panel / PV Efficiency – The percentage of available sunlight that is able to be converted into electricity by a solar panel. PV panel efficiency now lies anywhere between 15-22%.
- Peak Watts – Maximum possible power output under standard testing conditions.
- Polycrystalline – Composed of fragmented silicon melted together to form multicrystalline cells. They are slightly less efficient than monocrystalline panels, typically are blue in color, and have rectangular shaped cells. They are typically sold at a slightly lower price point.
- Power Rating – The amount of power produced under ideal standard testing conditions.
- Premier Panels – Tier-one, high-efficiency modules produced by well-known, name-brand manufacturers, usually at a higher price point. Examples would be LG, Panasonic, and Sunpower.
- PTC – Testing conditions developed by the National Renewable Energy Laboratory to simulate real world conditions. The temperature of the solar cells is set to 45 degrees Celsius to simulate heating from sunlight. Ambient temperature is 20 degrees Celsius with winds of 2.2 mph. As internal temperature rises in solar cells, the panel power output drops in comparison to standard testing conditions in a lab.
- Single-Crystal Structure – The molecular lattice of the crystal is linear and unbroken, making a continuous, uniform structure.
- Solar Shingles (or Tiles) – Solar photovoltaic modules designed to look and function as roofing shingles while simultaneously producing electricity.
- Standard Testing Conditions (STC) – Used for uniformity in comparisons of panels in a laboratory environment. Under STC: irradiation = 1000 W/m², temperature = 25°C, AM = 1.5 (air mass).
- Temperature Coefficient – Temperature coefficient indicates what percentage of the panel’s power output will drop by for every degree above 25 degrees Celsius (ex -0.52%).
- Thin-Film Solar Panels – Solar panels made with thin layers of material placed on a glass, plastic, or metal substrate. These are typically the cheapest and least efficient of all panel types.