The sun doesn’t just provide warmth and light – it’s also a source of energy.
Solar energy (or solar power) is the energy we generate from sunlight. Through a process known as the photovoltaic effect, we can convert energy from the sun’s rays into electricity that can power our TVs, refrigerators, lights and other appliances.
To generate solar energy for your home or office, you need a solar power system.
There are other key components to a solar system aside from the panels themselves.
To generate your own energy, you need a complete solar power system. The essential components:
You also need a method to store the energy generated by the panels. If you have access to power lines, this doesn’t require additional equipment. It can simply be fed into the utility grid and used later.
But if you are off the grid, you’ll need additional parts:
These are connected by smaller components like wiring, fuses, and disconnects.
You can also add equipment to monitor your system’s output online, which helps troubleshoot any issues with shading or defective equipment.
Here are some reasons why you might choose solar over another source of power:
Here are some drawbacks to consider before going solar:
The first thing to decide when you go solar is whether you need a grid-tied or off-grid system.
Each has a distinct benefit:
Grid-tie systems save money on your electric bill. It’s less expensive than buying electricity from the utility company. We recommend this to everyone by default if they can connect to the utility grid. Always build a grid-tied system if you have access to power lines!
Off-grid solar is for delivering power to remote properties without easy access to power lines. They cost more (due to the addition of batteries), and the main value is delivering power to a remote location.
There’s a third system type as well, which is a hybrid of the first two: it connects to the grid, but also includes batteries. Solar companies refer to these as either battery backup or energy storage systems. There are two main benefits:
Energy storage systems provide extra peace of mind and get the most from the electricity you generate. It’s up to you to decide if it’s worth it to spend more on your system for the added flexibility.
Grid-tie solar systems store the power they generate in the public utility grid. In return, the utility company credits your account for the power you generate. Those credits can be claimed to draw power from the grid when the sun isn’t out (at night or during poor weather).
Every utility company has their own policy which outlines the rates at which solar customers are credited and billed for power. This agreement is known as a net metering policy.
In many cases, the utility will buy and sell electricity at the same rate. But some utilities may buy power from solar customers at reduced rates, which has a real impact on the ROI of going solar. So it’s important to contact your utility and understand the terms of their net metering policy.
Solar cells are made primarily from silicon, a chemical element with conductive properties. Exposure to light changes silicon’s electrical characteristics, which generates an electric current.
A cell is a small square of silicon (about 6” x 6”) with electrical contact plates on the face. Solar panels are made by laying out a grid of these cells on a protective backsheet and covering them with glass on the front.
It takes multiple panels to provide power to a typical home or office. A collection of panels in your system is called an array. Panels wired into the same inverter are known collectively as a string of panels. (Inverters have a maximum string size, an upper limit to the number of panels they can support.)
For example, you may have a system with two inverters supporting two strings of 10 panels each, which comes together to make a 20-panel array.
Most manufacturers guarantee under warranty that their panels will be at least 80% efficient for 25 years.
When the warranty is up, the panels don’t break down. They simply keep working at a reduced output. A panel that is rated at 300 watts, for example, would still produce 240 watts of output at the 25-year mark.
Panels tend to be extremely reliable. A study by NREL (National Renewable Energy Laboratory) showed that over 75% of panels outperformed their warranty.
However, other parts like inverters and batteries have a shorter lifespan. You should expect to replace these parts at least once over the life of ownership, and those replacements should factor into total costs over the life of the system.
Inverters are warrantied for 10-20 years. Expect to replace your inverter once or twice in your system’s lifespan.
If you include batteries with your system, those will also need to be replaced. Lead-acid batteries typically last 3-7 years depending on how well you maintain them. Lithium batteries are warrantied for 10-15 years.
60-cell panels measure 39” by 65”, while 72-cell panels are 39” by 77”. In reality, these dimensions can fluctuate by up to an inch because manufacturers use different frame sizes. But the 60 and 72 cell layouts are standardized across the industry.
There are also smaller options for RV / mobile use, and some companies (like Panasonic) are experimenting with larger 96-cell panels, but these sizes aren’t common enough to be standardized at the moment.
There are two established cell technologies that dominate the market: monocrystalline and polycrystalline solar cells (mono and poly, for short).
Mono cells are cut from a single source of silicon, while poly cells are made by blending multiple bits of silicon into a single cell.
Since the composition of poly cells is less “pure,” they tend to be slightly less efficient on average. However, this isn’t a hard and fast rule, since other factors affect solar cell efficiency as well.
In addition to mono and poly panels, there are several emerging technologies to keep an eye out for, like thin film and bifacial panels.
The concept of solar panel efficiency is often misunderstood. Most panels have an efficiency rating in the range of 15-25%, which sounds really low without context.
Some people hear this and think, “wow, I only get 20% of the production from my panel? That sounds like a waste.” The assumption is a 100-watt panel would only produce 20 watts of power. But that’s not what we mean when we talk about efficiency.
In reality, the efficiency rating measures how much of the sun’s potential energy is converted to solar power. Using the same example, a 100-watt panel with a 20% efficiency rating will absorb 20% of the potential 500 watts of continuous power coming from the sun.
Don’t sweat too much about panel efficiency. The only real benefit to more efficient panels is that they fit more solar in less space.
High-efficiency panels matter if you’re trying to build in a tight space, but there’s nothing wrong with building a larger array with less efficient panels. The latter option typically reduces the overall cost of the system (because less efficient panels have a lower cost-per-watt, all other things being equal).
A solar inverter converts DC (direct current) into AC (alternating current).
Solar panels generate DC power, but most household appliances run on AC power. The inverter simply takes the energy you generate and turns it into a format that can power your electrical loads.
In micro-inverter systems, there is no centralized inverter. Instead, each panel is hooked up to its own micro-inverter.
In essence, every panel + micro-inverter pairing is like a self-contained solar system. Panels can be added or removed without impacting the performance of the rest of the system.
Due to this design, micro-inverters are a great way to start small and expand your system down the road. They also provide the same control and monitoring capabilities offered by power optimizers.
String inverters are the simplest and least expensive option available. Strings (or groups) of panels are wired together in series, with each panel chained to the next. The last panel plugs into a string input on the inverter.
Due to how they are wired, each panel in the string is on the same circuit, which means each panel in the string performs at the same level. If the output of one panel drops (due to shading or malfunction), the rest of the string suffers production drop along with it.
Because of these limitations, we only recommend string inverters if your system is fully exposed to sunlight. If trees or other obstructions will cast shade on your panels, you’ll be better served with an inverter that includes power optimization technology to mitigate the production loss.
Power optimizers can be attached to your solar panels, allowing the system to control each panel’s output independently from the rest of the string. If a single panel under-produces, optimizers ensure the other panels in the string are not affected.
Every solar energy system needs a method to store the power generated by the panels. With grid-tie systems, you can feed that energy into the utility grid, essentially using the grid as a giant battery.
Under a net metering agreement, the utility credits you for anything you contribute, and you can use those credits to withdraw power from the grid whenever you need it. With the grid serving as an energy storage system, grid-tie systems don’t need batteries to function.
Off-grid systems are different. Without grid access, you need to store your own power, and that means batteries are mandatory. Off-grid systems are quite a bit more expensive due to the inclusion of batteries, but can still be cost-effective as an alternative to running power lines to a remote property.
Grid-tie systems don’t need batteries, but adding them still has its benefits. The main benefit is backup power in case the grid goes down (which can happen frequently in places with severe weather or unreliable power grids).
By default, grid-tie systems don’t protect against power outages. Since the system is hooked into the grid, it must be configured to shut down when grid power goes out. This is a safety measure to protect utility workers from coming in contact with live wires while they work on the grid.
By adding energy storage, your system can stash a small amount of backup power in a local battery bank to keep the lights on during an outage.
Batteries have other benefits as well. For example, they can store power temporarily and sell it back to the utility when time-of-use rates are higher, ensuring you sell power to the utility at peak rates.
So where should you mount your panels?
Our default choice is to put them on your roof if you have room. Rooftop solar is less expensive to install because the support beams act as a foundation for the mounting hardware. You save on materials and labor because you don’t need to build a substructure to hold the weight of the array.
The alternative is a ground mount—a standalone metal or aluminum framework built somewhere on your property to mount the solar array. Ground mounts cost more because you have to buy the pipe for the frame, but they are easier to access for maintenance and repairs (no climbing on your roof).
A pole mount is simply a tall pole that lifts your solar array higher off the ground than a traditional ground mount.
Pole mounts are great for snowy climates. The elevated mount gives the array extra clearance, so the array doesn’t get buried in a snow bank during the winter.
Pole mounts can also be tilted at a steeper angle, which helps snow buildup slide off the face of the panels, keeping them free of obstructions and producing closer to their peak output.
Your system size depends on your energy usage, which is measured in kilowatt-hours. You can find this info on your electric bill, or in your online account with your utility provider.
Sizing is a complex process, but fortunately there are plenty of online tools to help you out.
A panel string is a group of panels wired into a single input on your inverter. Because the inverter has a voltage input limit, part of the system design process is calculating the ideal string size to maximize production without overloading the inverter.
In most cases, solar energy costs less than what you pay the public utility for electricity. Let’s do the math.
The utility company bills you for electricity. The national average is about 12 cents per kilowatt hour (kWh) of electricity used.
A kWh is simply a measurement of how much electricity you use. You can check your energy bill to find out how much you use each month in your household.
(Rather have someone do the math for you?
If you use 1,000 kWh / month billed at 12 cents / kWh, the power bill comes to $120 every month. That’s $1440 per year.
Now let’s look at how to get that done with solar. We’d recommend something like this 7.8 kW system, currently listed for $9,791 at the time of publication. It would cover 100% of the energy usage outlined above.
The federal tax credit shaves 30% off the purchase price, so you pay $6,853.70 for the equipment. (To claim the credit, you must owe taxes.
By generating your own power, you get to pocket $1440 every year that you are paying to the utility every year. After 4.76 years, you break even on savings. This is known as the “payback period” – how long it takes for your system to pay for itself.
Lastly, panels are warrantied for 25 years. Over the life of the warranty, the system pays back your investment 4 or 5 times.
Not only is solar energy good for the environment, but it also makes financial sense.
Solar panels require very little maintenance. Most of it is centered around clearing debris off the panels, which would block sunlight from hitting the solar cells and hinder production.
In cold climates, snow can pile up on your panels. Use a soft brush or broom to wipe them down without scratching the glass surface.
Same goes for dry climates where dust can settle on the panels. It’s a good idea to wipe down the panels a few times a year to clear off dust and debris. In more temperate climates, once a year is probably fine.
That’s about all there is to it. Solar panels are very durable because there are no moving parts, so there’s very little maintenance on the mechanical and electrical systems. If you keep panels clear, your system needs very little oversight.
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