These bifacial PV modules from Sanyo can absorb solar energy reflecting off the light-colored roof to generate electricity from the backside, boosting module efficiency. Photo by Dan Chiras.
Every year we hear about a breakthrough in solar electricity — usually a new solar cell with a very high efficiency rating. Knowing that new PV technologies are on the horizon, many people ask us if they should wait a bit before they invest in a solar electric system. Does it make sense to delay your installation until the new, more efficient PV technologies hit the market?
This is a fair question, but the answer is no.
Newer, more efficient PVs are certainly on their way, however, one of the key considerations when installing a PV system is not the efficiency of the PV modules, but the cost of the modules based on the installed capacity. Those of us in the business refer to this as the cost per watt of installed capacity.
An even better measure is the cost per kilowatt-hour of electricity produced by a PV system array over its lifetime. What you’ll find when comparing modules by these parameters is that new technologies, while more efficient, typically cost more per watt of installed capacity. A 2 kW system that utilizes the most efficient modules on the market, for instance, may cost 10 to 30 percent more to purchase than a 2 kW system that uses slightly less efficient modules. Yet both arrays produce the same amount of electricity. Why pay more to produce the same amount of electricity?
In some cases, though, a higher installation cost actually results in a lower cost of kilowatt-hour of electricity over the life of the system. PV modules fitted with micro-inverters, that is, small inverters mounted on each module, for instance, may cost more per watt installed capacity, however, the increase in efficiency may result in a lower cost per kilowatt-hour. So, if you are considering a solar electric system be sure to analyze your decision using both cost per watt installed capacity and cost per kilowatt-hour over the lifetime of the system. A competent installer should be able to do this for you.
Even if efficiency doesn’t result in greater output, it is an important consideration if space is limited. If meeting your electrical needs requires a 3 kW PV system, and the only place with good solar access you have to mount the modules is on a small garage roof, you may need to install the more efficient — and expensive —modules.
While conversion efficiency may not matter to you, efficiency is driving the market and over the long haul will result in more efficient and hopefully less expensive modules. Those companies that can produce higher efficiency modules at a lower cost with less raw material in an environmentally friendly manner stand to make billions.
Contributing editorDan Chirasis a renewable energy and green homes expert who has spent a lifetime learning life’s lessons, which he shares in his popular blog, Dan Chiras on Loving Life. He’s the founder and director of The Evergreen Institute and president of Sustainable Systems Design.