Despite its promise as a clean energy source, there a number of disadvantages of solar power that have prevented it from becoming widely used. Solar power isn't always as reliable as other forms of electricity and tends to be expensive to install and maintain. Most experts believe that further technological advances are needed to make solar power both accessible and practical. Some governments offer subsidies to offset the price, however, and engineers and scientists continue work to improve the technology.
Economic Factors
The expense of buying and installing the equipment is one of the major disadvantages of solar power. Each individual panel is not that efficient, typically converting just 10% to 18% of the sun's energy into electricity. It often takes 15 to 20 panels to generate enough electricity to power an average-sized home; the number required varies depending on how much electricity is required, how much sun the house gets, and many other factors. Bigger panels that can generate more electricity also cost more.
On top of the price of the panels themselves, the cost of installing them varies greatly by location, how many panels are required, where the panels are being installed, and other factors. By most estimates, it takes at least six years for the initial costs to be repaid in savings from power generation under the best circumstances, and double that time under less ideal conditions.
Reliability
One disadvantage of solar power is its lack of consistency and reliability. Solar-powered devices rely on a steady supply of sunlight to generate electricity; as soon as the sun goes down, light stops hitting the solar panels and the power drops instantly. On cloudy days, there is also less light available to produce electricity. This means that some form of storage technology — usually batteries — or an alternative source of energy is always required to ensure uninterrupted power flow. Some people who use solar power remain hooked up to an electrical grid to receive energy when no solar power is available.
Any obstruction between the sun and the panel can also reduce the amount of energy produced. To work at their best, solar panels need to be in a location where they are not shaded by trees or buildings. Sunlight can penetrate 1 inch (2.54 cm) or so of snow to produce energy, but the panels probably won't work as efficiently; any additional snow buildup during the winter is likely to prevent them from working very much at all.
Damage to Panels
Solar panels are susceptible to damage from the elements, another of the disadvantages of solar power. The constant bombardment of ultraviolet (UV) rays and other solar radiation often causes the panels themselves to deteriorate, much like any other material left exposed to the sun for extended periods of time. There have been improvements in how they are made, however, and their current lifespan is 25 to 30 years as of 2012. Still, blowing dirt and sand may damage the panels, as can large hail. It also may be possible to cause damage while clearing away heavy snow and debris if a homeowner isn't careful.
Batteries and Safety Concerns
Because it is not possible to make solar power 24 hours a day, most systems use a bank of deep cycle batteries to store excess power for use at night and on cloudy days. Unfortunately, these batteries can be expensive and have a shorter lifespan than the solar panels themselves. They also present some safety risks and require special handling, depending on the type of battery used. The least expensive and longest lasting — flooded lead acid batteries — also require the most maintenance and careful handling, as they can spill acid or explode if not stored correctly. The other two most common types, gel and absorbed glass mat (AGM), are less dangerous but typically much more expensive.
As an alternative to battery banks, some solar power systems are tied into the electricity grid. This allows the system to draw power when needed, and in many cases, send power back to the grid when the solar system produces more than the building needs. One of the safety-related disadvantages of solar power systems of this type is "islanding," which occurs when the system continues to generate electricity in power lines that electric company employees may assume are dead. This is an electrocution risk for the employees, though many areas now require solar power systems to include an anti-islanding component to prevent this from happening.
Addressing the Disadvantages of Solar Power
Despite the disadvantages, many governments, scientists, and activists continue to work on ways to make solar power more affordable and efficient. Improvements in battery technology have made storing the electricity generated by solar systems easier, and grid tie-ins allow people to sell power back to their electric companies. Flexible solar panels, although typically less efficient than those made with glass, are less likely to be damaged. Many governments also do their part to encourage the use of solar energy by subsidizing solar panel production and offering tax breaks to individuals who purchase solar panels for their homes.