Solar panels convert the sunlight hitting your roof directly into electricity, with no smog-forming pollution or climate-warming carbon dioxide emissions. Compared to a big, industrial power plant burning coal dug up from the ground, solar power systems seem like magic – but how do they actually work with your home electrical system?
Let’s follow the journey of a beam of light from the sun to your power outlet.
Solar Cells and the Photovoltaic Effect
The basic unit of a solar panel is a solar cell, which consists of two layers of silicon-based semiconductor wafers. When struck by the photons in sunlight, electrons in the silicon wafers are activated and knocked loose. This is called the “photovoltaic effect,” since it produces voltage from photons - and, believe it or not, this effect was discovered way back in 1839, and the first solar cell was created in 1884.
(It’s kind of amazing that it’s taken us this long to tap into the sun in a big way, but better late than never!)
Of course, you can’t do much with loose electrons zooming around on their own. They need structure! To provide it, solar cells have positively and negatively charged sides (called a cathode and an anode), which causes those rambunctious electrons to flow in a steady electrical current between them along a circuit. Now they’re ready to get to work!
From Solar Cells to Solar Panels to a Solar Roof
Each solar cell only produces a tiny bit of power - a few watts - but there’s strength in numbers. So dozens of solar cells get packaged together into solar modules, which in turn are packaged into solar panels with protective glass casing and insulation to ensure reliable performance.
An average solar panel for a residential system might be rated at 200 to 300 watts of peak power production capacity - not bad, but still not very much when you consider that a single old incandescent light bulb can consume 100 watts all by itself.
Thus, in order to supply a significant portion of your home energy use, a typical rooftop solar power system might include a dozen or so panels and produce 3 to 5 kilowatts of electricity in total. These solar panels are mounted on your roof and arranged to maximize their exposure to direct sunlight - which usually means avoiding shade (whether from trees or buildings) and facing south.
Choosing the Right Solar Panel
There are a head-spinning number of solar panels to choose from out there, including lots of good options at a wide range of price points. There’s no one “best” solar panel - instead, you want to consider your own specific situation, including your budget, your available roof space, and the typical weather conditions where you live.
One of the most important characteristics of a solar panel is its efficiency, or how good it is at converting sunlight into electricity. Typically, today’s home solar panels range from 15% to 22% efficiency - which might not sound like a lot, but represents a significant improvement over solar panels a decade ago, and is plenty good enough to save you lots of money on your electricity bill!
Like most things, you get what you pay for in terms of solar panel efficiency - in other words, you can expect to pay a premium for the most efficient brands. But when deciding what solar panel makes sense for you, you need to consider not only your budget but your available roof space. If you have a lot of room, you could potentially install more, less efficient solar panels and get better value for your money; on the other hand, if you have limited roof space, you might want to consider a smaller installation with more efficient panels.
Another important factor is the weather conditions where you live. If you live in the northeast, you’ll want to make sure you choose a solar panel with a high rating for snow loads; if you live in a windy area, you need a solar panel with a good wind load factor. These ratings and other issues relating to durability can get technical fast, but a good solar installer will be able to help you make the right call.
Mosaic provides you with an extra layer of assurance by working with a terrific network of trustworthy installer partners, as well as being careful to only provide loans for high-quality equipment packages. You can learn more about our home solar loan process here.
Inverters Bring Solar Power Into Your Home (and the Grid)
So, we know how solar panels generate electricity on your roof - but how does that electricity get into your house? And how does it all connect to the electricity grid?
The short answer is: an inverter. The (slightly) longer answer requires understanding the difference between DC and AC power.
DC, or direct current, flows in only one direction. This has the advantage of being more stable and efficient for transmitting power, and Thomas Edison himself advocated for it as the standard for public electricity grids. By contrast, AC, or alternating current, actually switches direction many times a second, and this was advocated by Nikola Tesla and George Westinghouse for its advantage of allowing the current’s voltage level to be easily shifted for different uses - up for long-distance, high-voltage power lines, and down for safe use in the home.
The struggle between Edison and Tesla and Westinghouse was so intense it became known as the Current Wars, but we’ve arrived at a happy truce: our electric grid and home electricity systems run on versatile, safe AC power, and sensitive electronic devices like computers and LED lights use transformers to convert the current from your socket into more stable DC current.
The electric current that solar cells produce is DC (just think of those orderly electrons marching in a line through a solar cell) so it needs to be converted to AC power in order to work with your home electricity system and the wider grid. That’s what inverters do: like a transformer in reverse, it “inverts” the DC power into AC power that you can use - or send back to the grid.
This compatibility with the grid is important, because for a variety of reasons most solar homes only use solar to provide a portion of their electricity needs, relying on local utility supplies for backup when the sun isn’t shining or if extra power is needed. Thanks to the magic of inverters, electricity produced by these panels is integrated seamlessly into your existing electricity service, so you can go solar without having to worry about your lights dimming every time a cloud passes overhead.
Choosing the Right Inverter
It should be noted that there are two types of inverters commonly found in home solar power systems: string inverters and microinverters. String inverters are more common, and they take the aggregated DC electricity from all of your solar panels and convert it to AC at a single point. By contrast, microinverters are built into every single solar panel and convert to AC at the panel level.
In general, string inverters are less expensive overall, but microinverters may have an edge in system efficiency - especially for installations that are partially shaded or may otherwise have differing output from different panels. Your installer should be able to help you decide what’s best for your particular roof.
One more thing about inverters: if you want battery storage with your solar power system, or think you may want to add it down the line, you’ll want a “smart” or “hybrid” inverter capable of intelligently managing the flow of power from your solar panels to your battery to your home. It may add extra cost, but there are real benefits - learn more about battery storage (and Mosaic’s battery financing) here.
What About Maintenance?
While solar may seem like a complex, space-age technology, it’s also very easy to maintain. After all, there are no moving parts, so you don’t have to worry about wear and tear, and solar power system components are built to last for decades.
Your main concern is simply keeping your solar panels clean and free of dirt, grime, and bird droppings, all of which can reduce the generation of your system. Regular rain can do a pretty good job all by itself, but you might have to hose them off every now and then if you live in a dry part of the country.
If you can’t clean your solar panels without getting up on the roof yourself, you should simply have your system inspected on a regular basis to ensure that your solar power system is operating at maximum efficiency throughout its long life. That’s why some installers include maintenance in their home solar installation packages.
Going Solar Works
We’ve just given you a ton of information on how solar panels work, which should give you more confidence when thinking about going solar yourself. But at the end of the day, all you really need to know about solar PV systems is that they work seamlessly with your existing home electricity supply – the only difference you’ll notice is a lower monthly utility bill!
And Mosaic can help you get those space-age, money-saving solar panels on your roof in seven easy steps - click here to learn more about financing your 100% clean energy home.