The ultimate guide to solar energy


Solar panels on a field in front of a cityscape
Below - everything you need to know about solar energy.

Solar energy is arguably the most important energy source available to humankind.

As the world searches for clean and effective alternatives to dirty fossil fuels, nothing has generated as much buzz as solar. In fact, solar energy is now the fastest-growing source of electricity in the U.S. with a 25% increase in solar capacity in 2021 alone.

With its popularity on the rise, now is the best time to learn more about solar energy. Luckily, you're in the right place to do just that.

This guide tells you everything you need to know about this exciting energy source, covering solar energy basics, the best places to study and research solar, and the best solar companies to buy solar panels from.

Calculate how quickly a solar installation would pay for itself after rebates

Solar energy at a glance

  • Solar photovoltaics (PV) panels – known simply as solar panels – are the most popular method of creating usable power out of solar energy.
  • Solar is an excellent source of renewable energy: it’s clean, abundant, cost-effective, and very versatile.
  • Solar power is highly scalable, so it can be used in everything from small solar-powered watches to gigantic solar parks.
  • There are many great solar learning resources available online. Here are our top recommendations: for solar technology basics, the SolarReviews calculator for a home solar estimate, and NABCEP and SEI for job training.
  • The best solar manufacturing companies are Qcells, LONGi Solar, Canadian Solar, Jinko Solar, and SunPower Maxeon.

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    Solar energy basics

    What is solar energy?

    Solar energy describes the heat and light energy carried by the sun’s rays.

    Solar energy is what makes life itself possible on Earth. The warmth and light provided by the sun create a climate hospitable for life. Without it, no living creature can survive – not plants, not animals, and certainly not humans.

    While we have always relied on solar energy, in more recent times we've developed modern technologies that can harness it for usable heat and electricity. It is rapidly proving to be a practical and cost-effective source of renewable power, which means it has a huge role to play as we urgently seek to end our current reliance on climate-destroying fossil fuel energy.

    However, to properly understand this exciting energy source there are a few important technical terms you need to know:

    • Solar: Anything related to the sun. The sun is the star of our solar system and the source of all warmth and light on planet Earth.
    • Solar energy: A broad term to describe energy generated by the sun and emitted as electromagnetic radiation, i.e. sunlight.
    • Solar power: Energy from the sun that has been converted by humans into usable energy, in the form of either electricity or heat. The terms "solar energy" and "solar power" are often used interchangeably.
    • Solar electricity: Electricity produced from sunlight. It can be created using either solar thermal or solar photovoltaic technology.
    • Solar thermal: Heat energy collected from sunlight. Solar thermal energy can be used for energy storage, heating, or electricity generation.
    • Solar photovoltaics: The process by which electricity is created out of sunlight using solar panels. The panels are made of solar cells containing special semiconductor materials.

    Learn more: How do solar panels work?

    What makes solar such a great source of renewable energy?

    Solar is classified as a renewable energy source because there’s no way we can use it all up. No matter how much sunlight we capture for use, its supply will be renewed by the continuous radiation sent towards us by the sun.

    Furthermore, we won't run out of sunlight any time soon. According to NASA, the sun will continue to shine for the next 5 billion years or so.

    Here are the other major advantages of using solar energy for our power needs:

    • Solar energy is clean: Solar is very environmentally-friendly. No emissions or waste products are created when solar is used to generate electricity or heat.
    • It's abundant: An immense amount of raw solar energy hits the Earth at all times – there is more of it available than any other energy source.
    • It's cost-effective: The International Energy Agency recently declared solar power is now the cheapest type of electricity in history thanks to improvements in technology and manufacturing.
    • And very versatile: Because the only input required is sunlight, it is possible to generate solar power almost anywhere. That makes it practical to use it in an almost endless number of applications, including handheld devices, rooftop energy systems, utility-scale plants, and even interplanetary spacecraft!

    This unique combination of benefits makes solar energy an attractive renewable energy option as we seek to move away from fossil fuels.

    What are the different methods of generating solar power?

    Solar energy is harnessed and converted into a usable form using three main methods:

    • Solar panels that use solar photovoltaic technology
    • Concentrated solar power (CSP), a solar thermal application
    • Solar water heating, which is another form of solar thermal energy

    1. Solar panels (solar photovoltaics)

    Solar panels – also known as photovoltaic (PV) solar panels – are the most popular way to use solar energy for electricity generation. There are currently more than 3 million solar panel installations across the U.S, and the number is growing quickly.

    Solar panels consist of a series of special semiconducting solar cells that use the photovoltaic effect to convert photons in sunlight into direct current (DC) power. The DC power generated is usually fed into a solar inverter, where it is converted into alternating current (AC) electricity – the type of power used in our homes, and across the electric grid in general.

    You can install as many solar panels as you need to meet your power requirements.

    2. Concentrated solar power (solar thermal)

    Concentrated solar power (CSP) is a technology that uses special reflectors to generate electricity at a large scale.

    CSP plants use thousands of special mirrors called helioscopes to reflect sunlight onto a central collector. There, the sun's heat energy is collected in a heat storage medium like molten salt or used to generate electricity via a steam turbine.

    Unlike PV plants that create power out of light, CSP power plants capture heat from the sun. CSP plants are thus known as solar thermal plants. They are also called "power towers" and "salt tower plants" because of their distinctive tall towers.

    CSP technology is expensive, and it is impractical to use it at the residential or commercial level. However, it is considered a promising technology at the utility scale since it can be used as a means of energy storage.

    3. Solar water heating (also solar thermal)

    Solar water heaters are another way to make use of solar thermal energy. Here, rooftop solar thermal panels – not to be confused with PV solar panels – are used to heat water stored in an insulated cylinder.

    Solar hot water systems can supply most of a home's hot water needs, even when it's cold outside.

    Three common solar project types

    For classification purposes, solar energy is generally divided into three common types: residential, commercial, and utility-scale.

    • Residential solar: This refers to solar energy generated on homes, usually with rooftop solar panels. Residential solar panel systems are usually between 4 kilowatts (kW) and 16 kW in size.
    • Commercial solar: Also known as Commercial & Industrial (C&I) Solar, this describes the use of solar energy by businesses, government agencies, and nonprofits. Commercial solar systems between 10 kW and 100 kW in size are most common, although companies like Apple and Amazon have many times this amount after making massive investments in solar capacity.
    • Utility-scale solar: This covers large solar power plants that produce electricity at a mass scale for the electric grid. The U.S. Energy Information Administration (EIA) considers a power plant to be utility-scale if its total generation capacity is 1 megawatt (MW) or greater.

    Solar energy is highly scalable, making it a practical and cost-effective energy solution for projects of all sizes. At the smallest scale, you can find it powering devices like watches and calculators. At the other extreme, it is deployed in gigantic solar parks that use hundreds of thousands - or even millions - of solar panels.

    What are solar batteries and how are they used?

    Solar batteries are special products designed for the effective storage of solar electricity. They efficiently store solar energy at the time of production, and quickly discharge when it is required.

    Here’s how they work with most homes: As solar panels generate energy, any electricity the home doesn’t immediately use is sent to the battery to be stored. Later, when the panels aren’t producing power, the battery can discharge its stored energy and power home appliances. A solar battery can also be used as a source of backup power in the event of a blackout.

    For a more in-depth look at how solar batteries work to power your home, check out this video:

    At the residential level, a rising proportion of consumers are adding lithium-ion solar batteries like the Tesla Powerwall and LG Chem RESU batteries to their solar panel installations. While they are more expensive than other battery types, like lead acid batteries, lithium-ion batteries are safer, last longer, and require less maintenance.

    Energy storage is key to a clean energy future. Solar on its own is an intermittent resource, meaning it can only produce power when the sun is out. This is a problem because we consume energy all 24 hours of the day and actually use the most energy when the sun is down. Solar batteries overcome this issue by storing solar energy so it can be used at all times - even when the sun isn’t shining. Energy storage has a big role to play to make solar power one of our top energy sources.

    See if solar + battery storage is worth it for your specific home

    How much does a solar energy system cost?

    Here are the costs to buy a solar energy system in 2023:

    • A home solar panel system costs between $16,500 to $20,100, assuming a 6 kW system size and average unit cost of $2.75–$3.35 per watt.
    • A commercial solar panel system costs $82,000, assuming a 50 kW system and an average cost of $1.64 per watt.
    • A utility-scale system costs $850,000 to $1.01 million, assuming a 1 megawatt (MW) plant and average costs of $0.85–$1.01 per watt.

    The prices above show purchase costs before applying any incentives. Following the passage of the Inflation Reduction Act in 2022, these costs can be lowered significantly via the federal solar tax credit – effectively a 30% discount – and other incentives and rebates offered at the state, utility, and local levels.

    In terms of the purchase process, the tricky part is picking the right solar company – which is why we've made a video explaining how you should choose an installer:

    Once you've made your decision, you will pay the solar company upfront using either cash or a solar loan, and they'll take care of the rest.

    Solar panels come with long warranties and require minimal maintenance, so you're unlikely to have ongoing costs related to the system once it's been installed.

    How much does it cost to buy usable solar energy?

    The cost to purchase usable solar energy depends on how much power you are buying, and where you are buying it from.

    Generally speaking, the cheapest way to consume solar energy is by buying a solar panel system and producing it yourself. The way to check if that’s the case for you is by calculating your Levelized Cost of Energy (LCOE).

    If you can’t install solar panels – you may currently be renting, for instance – you can buy solar energy via a utility green power or, where available, a community solar program. Using the former option will cost you a bit more than standard utility electricity, while the latter should cost you a bit less.

    We explain all three options below:

    • Levelized cost of energy (LCOE) for home solar panels: The LCOE, represented in cost per kilowatt-hour (kWh), allows you to compare the cost of generating your own solar power against the cost of buying electricity from your utility. It is calculated by spreading your total system installation costs over the total forecasted energy production over the system's lifespan, which is typically 25 years. After applying incentives to a home solar system, the LCOE usually falls between $0.08 and $0.11 per kWh, and sometimes even lower. This is a lot less than what most customers pay for their utility power.
    • Buying green power from your utility: Under a green power plan, your utility promises that part of your electric supply, usually half or more, will come from renewable sources like solar. Your utility will charge you extra for this – typically a 10% premium over their standard electricity rates. Assuming you currently pay $0.20 per kWh for electricity, buying green power from your utility could cost you $0.22 per kWh. If we look at it by month, a $150 monthly electric bill might rise to $165 under a green power plan. However, green power rates can vary from utility to utility, so contact your provider for specifics.
    • Buying from a community solar program: Community solar programs allow you to participate in large solar projects and gain a small share of the benefits. Typically, you pay a monthly subscription fee to the operator of a community solar farm, and they assign you a portion of the solar power generated. Your utility will compensate you by lowering your electric bill, in a process known as virtual net metering. For instance, by paying you a $50 monthly subscription fee paid to a community solar provider you might see your monthly utility bill fall by $60, earning you a savings of $10 a month.

    5 best solar learning resources

    In this section, we’ll share the best free resources for learning and researching solar energy. Here’s what we’ll help you find:

    • An intro to solar energy tech
    • Solar research and tools
    • A calculator that assesses your home's solar potential
    • Info about the U.S. solar industry
    • Top solar job training providers

    1. Introduction to solar energy technologies – is the official website of the U.S. Department of Energy. It has information on all major sources of energy, including a section dedicated to solar energy.

    We highly recommend their series "Solar Photovoltaic Technology Basics," which does a great job explaining how solar panels are made, how they work, and how solar power systems are designed.

    2. Solar research and tools – NREL

    The National Renewable Energy Laboratory, or NREL, is a large, federally-funded research organization dedicated to renewable energy and energy efficiency.

    NREL has been working to advance solar for several decades now. It was founded as the Solar Energy Research Institute (SERI) back in the 1970s, and subsequently expanded its focus to include other energy sources, but solar remains its top area of study.

    NREL is a great place to learn about the latest solar research. They also offer solar data and tools free of charge, including these two excellent resources:

    • NSRDB: The National Solar Radiation Data Base (NSRDB) contains detailed meteorological data for the entire United States and many other locations worldwide. You can use it to see how much sunlight your location receives on average during a specific month, or over the year as a whole.
    • PVWatts: PVWatts is a web application that shows you solar panel production estimates for almost any location in the world. We have a handy guide that shows you how to use it to calculate the solar panel system size required for your home.

    3. Estimate your home’s solar potential – SolarReviews calculator

    Designed for easy use by homeowners, the SolarReviews solar calculator is a powerful tool that shows you the estimated costs and savings of installing a solar energy system on your roof. The following video gives a great overview of how you can use the SolarReviews calculator to get an accurate estimate of how much solar can save you:

    Using your address and average monthly electric bill, the calculator creates a personalized analysis of your home that tells you everything from what size solar system you need, estimated yearly electricity bill savings, applicable incentives and rebates, and even details about financing options.

    The calculator can provide such detailed estimates thanks to an advanced algorithm that utilizes vast troves of data. It pairs official meteorological data with multiple nationwide databases, allowing it to factor in your energy usage patterns, your utility electric rates, local incentives and rebates available to you, and even the prices offered by solar companies in your area into its calculations.

    To use the SolarReviews calculator to see a solar estimate tailored to your home, just enter your zip code below.

    Calculate the savings you would see from installing a solar energy system on your home

    4. Information about the U.S. solar industry - SEIA

    As the national trade association for solar, the Solar Energy Industry Association (SEIA) has valuable information on the state of solar countrywide.

    In particular, their solar market insight reports offer an excellent snapshot of the industry’s performance, while also analyzing key trends to be aware of.

    Other interesting topics covered on their website include:

    5. Solar job training - NABCEP and Solar Energy International

    The solar industry is one of the fastest-growing industries and it presents many career opportunities from tradespeople to finance executives.

    NABCEP (North American Board of Certified Energy Practitioners) establishes the most widely recognized training standards and curricula in the solar energy sector. NABCEP partners with individual training providers to design and deliver courses to professionals who are either already in the industry or seeking to join it. Their certifications apply to a range of different fields including solar panel installation, system design, inspection, sales, and maintenance.

    Solar Energy International (SEI) is the largest and best-known solar training provider. They offer both free and paid courses online and at their training center in Paonia, Colorado. A content team from SolarReviews – including this scribe – attended the intermediate solar training course and gained a great deal of technical knowledge from it. Their introductory online course can be accessed for free.

    The 5 best solar companies

    Differentiating between solar companies can be a difficult process. There are dozens of companies offering solar panels for the residential market with similar certifications, classifications, and product offerings.

    To overcome this challenge, SolarReviews developed a scoring system that ranked solar companies based on the criteria that really matter to consumers. Our rankings don't just factor in module quality and warranty, but also things like the company's long-term ability to offer warranty and after-sales support, and, most important of all, value for money.

    After conducting a rigorous assessment of all major solar panel brands, we found these five solar companies to be the best:

    #5 SunPower Maxeon

    SunPower Maxeon offers the very best solar panels on the market in terms of both panel efficiency and module quality. They also have an excellent network of dealers and installers, which means you can expect a high standard of workmanship on your installation.

    Given these strengths, why is SunPower Maxeon fifth on our list? A large part of it is the very high cost of their panels - they are substantially more expensive than the competition. The company has also been experiencing financial difficulties, raising questions about its ability to honor future warranty claims.

    Video: Expert review of SunPower Maxeon solar panels

    #4 Jinko Solar & #3 Canadian Solar

    Grabbing the next two positions, with virtually identical scores, are Jinko Solar (#4) and Canadian Solar (#3).

    The two companies are similar in many ways, including being two of the world's largest solar manufacturers, and relying heavily on Chinese manufacturing and R&D. They also earned top scores in our financial and value categories, as they are both profitable publicly-listed companies and offer panels at an affordable price.

    But there are some differences too. Jinko Solar wins extra points for operating a large plant in Florida but loses points for its disappointing warranties. Canadian Solar, meanwhile, has a weak corporate presence in the U.S., lowering its attractiveness to local buyers despite its many strengths.

    Videos: Expert review of Jinko Solar panels and Canadian Solar panels

    #2 LONGi Solar

    LONGi Solar, another solar Chinese solar giant, comes in at #2 on our list.

    Like the other top Chinese manufacturers, LONGi boasts advanced manufacturing processes, high-quality modules, and affordable prices. However, two factors made them a cut above the rest (and almost the very best): costs that are slightly lower than rivals, and superb technical specifications on their flagship modules, a combination that is hard to beat.

    The issue with LONGi is that while they're big globally, they haven't yet made a substantial dent in the American solar market, and as such only a limited number of dealers carry their products.

    Video: Expert review of LONGi solar panels

    #1 Qcells

    Earning the top spot with the highest overall score is Qcells, formerly a German solar company, but now owned by Korean conglomerate Hanwha.

    Here are the reasons the company scored so highly:

    • Strong financial position: Both the parent Hanwha Group and Qcells solar division report healthy operating profits, maximizing the likelihood of receiving after-sales and warranty services in the long term.
    • Highly committed to the U.S. market: Qcells is the largest manufacturer of residential solar panels in the U.S. with a gigantic 1.7 gigawatt (GW) assembly plant in Dalton Georgia, with plans to expand local production capacity further.
    • Excellent dealer network: Qcells solar panels command a high share of the U.S. residential market; you should have no trouble finding top-rated solar installers offering them in your area.

    Video: Expert review of Qcells solar panels

    For a more detailed discussion on what makes these companies so good, and how to choose between them, check out the video below.

    *While the video above awards the #1 ranking to LG Solar, we have excluded them from this article after they announced their exit from the solar manufacturing business.

    Thinking of getting solar panels for your home?

    If you’re thinking about going solar, the best place to start is by getting a solar estimate for your home. This will provide you with all the key details you need to help you decide if it’s a good idea, including the system size you would need, what it will cost you, and how much you can expect to save.

    You can receive a personalized estimate by providing your home address and your average monthly bill - start by entering your zip code below.

    Check whether a solar installation would be worth it for you with our calculator
     - Author of Solar Reviews

    Zeeshan Hyder

    SolarReviews Blog Author

    Zeeshan is passionate about promoting renewable energy and tackling climate change. He developed these interests while studying at beautiful Middlebury College, Vermont, which has a strong focus on sustainability. He has previously worked in the humanitarian sector — for Doctors Without Borders — and in communications and journalism.

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