On a cost per Watt basis, solar energy is the most expensive electricity-generation method when compared to hydro, coal, nuclear and even wind power. That's why commercial solar power generation plants are not readily built. Even with the latest advances in semiconductor material, a single solar cell still generates a relatively small amount of electricity. A large surface area is also needed to make the installation worthwhile. An entire rooftop may be needed to be covered with solar panels to provide enough energy for one household. Technological advances are needed in order to make solar energy generation more efficient, smaller in size, and more affordable to the average homeowner.
For maximum efficiency, solar panels need to be perpendicular to the sun and require a mechanical alignment system to follow the sun across the sky. The maintenance of these orientation systems is extremely cost prohibitive for small installations. For large installations, the cost is extraordinary.
If the sun isn't shining brightly in the sky, then a solar panel won't generate electricity. Solar power is only generated during daylight hours and when the skies are clear. An overcast sky or even a passing cloud will severely reduce the production of electricity. Unfortunately, this type of inconsistent power supply doesn't fit well with the modern lifestyle. Energy is still needed by consumers after sunset and during inclement weather.
Expensive battery storage banks can provide power when the solar panels are dormant but need to have the capacity to meet the expected load. The larger the load, the more batteries are needed. If the following day is cloudy, the solar panels may not be able to fully recharge the energy reserve. This weather dependency usually relegates solar power systems to be supplementary power sources, off-setting electricity consumption from the grid. For these reasons, solar power alone is often considered a secondary source of power and insufficient on its own for homeowners wanting to go completely off-grid.
The main disadvantage of solar power is the economics. Semiconductor material from which the solar cells are made are prohibitively expensive to manufacture. Even as advances in material science and manufacturing methods are discovered, the fundamental techniques are highly cost prohibitive. There are cheaper solar panel material used in consumer electronics but they do not generate as much power as the classic photovoltaic cell.
Some recent discoveries allow for more of the solar spectrum to be used to generate power, but these experimental materials use the same expensive crystal growth and doping methods. Manufacturing improvements are still decades away.
For the past few decades, solar power generation stations have been operating under government sponsorship and have proven that generating electricity from the sun's energy is technically feasible but economically not viable, as least not yet. These installations are located in sparsely populated, arid deserts that receive sunshine almost all year. Large amounts of inexpensive land is required to accommodate the solar panels and mirrors which relegates these power plants to be located far from where the power is actually used. Expensive transmission towers need to span these distant power sources to energy-consuming, urban centers.
Despite the current disadvantages of solar power, harnessing the free energy of the sun still seems promising. As scientific advances and manufacturing techniques help make solar cells more efficient and cheaper to make, solar power will become an important energy source for residential homes in the future.