Though triple the number were sold in 2016 as were in 2012, the 144,000-plus plug-in electric vehicles (PEVs) that hit U.S. roads last year represent less than 1% of all new vehicles.

The Chevrolet Volt, Nissan LEAF and Tesla Models S and X buoyed sales by 30,000 over the previous year, an increase of more than 25%, according to the U.S. Department of Energy’s Alternative Fuels Data Center.

With PEVs making so many headlines, why do actual sales seem so miniscule? Experts point to a variety of reasons, but one hits home for many would-be PEV owners: Range anxiety.

Range anxiety refers to a potential driver’s fear that a PEV’s limited battery will be depleted before reaching a destination. With most PEVs’ ranges falling under 100 miles and charging stations few and far between, that fear is not unwarranted.

Though U.S. drivers travel just 40 miles each per day on average, most feel secure that their vehicles could take them several hundred miles, if needed, with little to no chance of running out of fuel or becoming stranded.

To combat this range anxiety, automakers have begun producing PEVs with longer ranges. Several can travel more than 200 miles, with the aforementioned Tesla Model X and S each boasting a range of nearly 300 miles.

But what will put PEVs on the same playing field as traditional gas-powered vehicles, most of which are capable of 500 miles or more? The answer seems to be better batteries.

While nickel-metal hydride, or NiMH, batteries powered early hybrid vehicles such as the Toyota Prius, lithium-ion batteries now power many of the rechargeable devices we use today, including most PEVs. They also can be found in most smartphones, laptops and home electronics. And for good reason: Lithium is plentiful, and its batteries lightweight and efficient. On the other hand, they are prone to combustion, as seen with the several PEV battery fires in recent years.

The tradeoff is favorable enough, however, that Tesla has built a 5.8 million-square-foot factory in Utah to produce the lithium-ion batteries that will power the 500,000 PEVs it plans to build by 2018. By then, Tesla boasts, its “Gigafactory” will be producing 35 gigawatt-hours of lithium-ion battery cells each year.

In the meantime, scientists and engineers will be working to improve energy density, the amount of energy stored by a battery in relation to its size. Some believe energy density could be doubled or even tripled within the next 10 years.

That means the same 7,000 lithium-ion cells that currently allow a Model S to travel 300-plus miles could, in the next decade, allow it to travel between 600 and 900 miles. Alternately, the amount of battery cells built into the vehicle could be halved, creating a lighter car that is more efficient, safer and cheaper.

While PEVs must overcome other hurdles in order to gain a larger market share, it seems likely that battery technology is the key to their continued growth.