Solar panel prices have plummeted more than 80 percent in recent years, but solar power is still more expensive than fossil-fuel power in most places, and accounts for a tiny fraction of the world’s energy supply. Few people have a better idea of what it will take to make solar compete with fossil fuels than Richard Swanson, who founded SunPower, a major solar company that sells some of the industry’s most efficient solar panels. During SunPower’s almost 30 years in existence, Swanson has seen many types of solar technology come and go. At the IEEE Photovoltaic Specialists Conference in Denver this week, he sat down with MIT Technology Review’s Kevin Bullis to talk about where the solar industry is now, and where it needs to go in order to become a major source of electricity.

How close is solar to competing with fossil fuels?

It’s darn close. In 2000, a big study concluded that solar panels could get below $1 per watt [a level thought to make solar competitive in many markets]. At the time, everyone in the industry thought the authors were in la-la land. Now we’re under that cost target.

It’s not like there’s one cost number and then everything is all good. The value of solar power varies widely, depending on local sources of electricity that it’s competing with, the amount of sunlight, and other factors. There are geographic pockets where it’s becoming quite competitive. But we need to cut costs by at least another factor of two, which can happen in the next 10 years.

What new technology will it take?

Solar panels now account for less than half of the cost of a solar panel system. For example, installers spend a lot of time and money designing each rooftop solar system. They need to have a certain number of panels in a row, all getting the same amount of sunlight. A bunch of companies are automating the process, some with the help of satellites. One of the most exciting things is microinverters [electronics that control solar panel power output] that allow you to stick solar panels anywhere on a roof—it’s almost plug and play.

To almost everyone’s surprise, silicon is still chugging along. The new developments are pretty amazing. Panasonic, Sharp, and SunPower just announced solar cell’s that break a long standing efficiency record. We need to do things like keep improving efficiency with new solar cell architectures, like the one Panasonic used. There are three basic new cell structures, and all of them are nearing or are already in production. We need to make thinner silicon wafers, improve ways of growing crystalline silicon. We need to switch to frameless solar panels because the cost of the aluminum frame hasn’t been going down much. We need to get rid of silver electrical contacts and replace them with cheaper copper. It’s tricky, but it can be done.

Is investment in research on batteries for storing solar power just as important as developing new solar cell designs?

Oh, yes. Not just batteries—other kinds of storage, too, like thermal storage. A wild card is the possibility of using batteries in electric cars to store solar power. That could change everything. People say that the battery industry will never meet the cost targets you need for this. But I come from an industry that just blew away cost targets. It’s hard for me to argue they won’t be able to do it.