How Efficient is Solar Energy? Factors that Affect Efficiency

Understanding how solar efficiency is measured helps to determine if you are getting the most from your system. Efficiency can be measured by the number of kWh (kilowatt-hours) of energy produced an "average" 150 watt solar panel of one square meter in size. How efficient is solar energy, and is it a viable option for homeowners?

The average solar cell efficiency is thought to be between 12% and 15%. The efficiency is dependent on many factors: how much sunlight it gets; the angle of the solar panels; whether parts of the cell are shaded; and how clean the solar panels are. Solar panel installations may produce only 1 kWh/m²/day, or they might produce as much as 8 kWh/m²/day or higher.

Keeping panels clean and free of dust and debris can help them to better absorb sunlight and produce more output. Likewise, you can help your solar panels by locating them in sunny areas that aren't shaded by trees, parked cars, buildings or other structures, since even a little bit of shading can dramatically decrease the cell's output. You will also need to tilt your panels to get the best exposure to the sun. Most homeowners just mount the panels in a fixed position, but there is a device known as a solar tracker that re-orients your solar panels as the sun moves across the sky. They add to the cost of a system, of course -- and they need to be properly maintained -- but they also help solar cells maximize output.

Many people are under the misconception that solar power is totally cost-free. Yes, the sun is free but the energy produced by a photovoltaic system is not. It's not uncommon for a system to cost tens of thousands of dollars. The significant initial investment is a big reason that solar power is primarily being used in remote areas that do not have access to traditional power companies. Over time, a solar powered system can pay for itself, however the initial price tag presents a steep hurdle for many homeowners. Optionally, and for a much smaller investment, homeowners could decide to use solar energy selectively within the home - for instance, the use of solar water heating - or if you're the handy type, you might decide to build your own solar panel for additional cost savings. On the positive side, solar panels often last 25 years or more.

Research is ongoing with strong beliefs that solar power will be cost-effective in the near future, but also competitive with traditional power companies and more widely used in urban areas. In 2007, a team lead by the University of Delaware, produced a record-breaking solar cell efficiency of 42.8% (the previous record was 40.7% efficiency). As solar cell efficiency continues to improve, look for solar power to become a much more attractive and cost-effective energy alternative for both homeowners and businesses alike.