Solar energy has come a long way since 1830, when British astronomer John Herschel famously used a solar thermal collector box (a device that absorbs sunlight to collect heat) to cook food during an expedition to Africa.  
Today, photovoltaic (PV) materials directly convert light into electrical energy without the need for turbines, generators, or other mechanical assistance. When a PV system absorbs sunlight, energy passes on to electrons. The energized electrons break free and, in the right conditions, join an electric current—which can then power your home.
PV systems for homes are most commonly made up of dark, flat panels placed on roofs. Smaller versions can operate individual lights or remote machines (such as irrigation pumps or traffic signs), while larger applications are able to power buildings or supply electricity to the grid.

What it costs
Over the past 20 years, the price of PV modules has tumbled, and with it, PV arrays are emerging as an ever-growing part of the nation’s renewable energy supply. According to the Solar Electric Power Association, the price of PV modules has plummeted from $9 per watt in 1992 to $1.15 per watt in 2012.
NearZero, a non-profit research institute based in Stanford, Calif., recently surveyed 21 experts about solar’s outlook. The consensus was that “for the next 15 years at least, PV prices will continue to head down.” According to the U.S. Department of Energy (DOE) Lawrence Berkeley National Laboratory, the total installed costs for residential PV fell substantially in 2011 and through the first half of 2012, by as much as 14 percent.
Commercial and utility-scale solar systems are seeing similar shifts—a setup that once necessitated an outlay of more than $3,600 per kilowatt just two years ago can now be put in for less than $2,000 per kilowatt.
As solar has become more affordable, more than a dozen cooperatives across the country, notably in Arizona, Colorado, Florida, Texas, and Utah, are constructing community solar “gardens”—centralized PV systems, segments of which are sold or leased to members—to meet growing consumer calls for solar alternatives. Other co-ops are investing in large PV farms as a way to diversify their generation mix and meet state renewable portfolio standards.
In addition, high-temperature solar thermal energy (concentrating solar power) has begun making some tiny inroads as a round-the-clock power source in the Southwest. The technology uses long troughs of shiny parabolic mirrors that concentrate the sun’s rays on receiver tubes filled with synthetic oil (or a tower containing molten salt). The fluid gets heated to as high as 750 degrees Fahrenheit before being pumped through heat exchangers to create steam that spins a turbine-generator. Concentrating solar power is seen by some as a possible way to stockpile renewable electricity for later use—the heated material can continue to produce power even when the sun doesn’t shine.
Access Energy Cooperative is one of those co-ops, harnessing the sun since last year on a small-scale basis. A 100kW solar array on the roof of our warehouse provides approximately 25% of our energy usage for the headquarters facilities.
“Although solar power remains more expensive and less reliable than more traditional forms of power generation, we’re excited about its potential,” says Bob Swindell, General Manager/CEO. “If you’re considering putting in solar panels, or any type of ‘backyard’ renewable generation at your home, make sure to contact us first to make sure the system meets our interconnection standards.”

The bottom line
Sunlight may look like an easy way to generate electricity, especially in remote areas without easy access to transmission lines. But there are drawbacks. The sun only shines for a set number of hours daily, and cloudy or overcast conditions can wreak havoc on solar power production. However, state and federal rebates for installation and declining equipment costs can make a PV system financially feasible in the right location.

Sources: Angela Perez; Solar Energy Industries Association, Lawrence Berkeley National Laboratory, U.S. Department of Energy, Solar Electric Power Association, NearZero