When the Toyota Prius cruised into North America for the first time in the early aughts, drivers were shocked. At a time when the average sedan got just 23 miles per gallon (and the average passenger car just 20 miles per gallon), the Prius got 48. Thanks to regenerative braking and the little electric motor, its city mileage was better than its highway mileage.

That was then.

Now, when it comes to miles per gallon, electric vehicles blow hybrid cars out of the water. The average electric car in the United States today gets the equivalent of 106 miles per gallon. And, according to a new report, that number could more than double in the next decades, to the equivalent of more than 200 miles per gallon.

That growth in efficiency could help ease the strain that electric vehicles are expected to place on the grid, extend battery range and even limit the need for public car charging. With a concerted push, the U.S. transition to EVs could be made smoother and billions of dollars cheaper for consumers, experts argue.

Without it, the country could face increased electricity demand equivalent to about a quarter of all current U.S. electric power use.

“It’s like walking by money on the sidewalk,” said Luke Tonachel, a senior strategist at the Natural Resources Defense Council and one of the authors of the report released Wednesday by NRDC and the Electric Power Research Institute. “We’ll miss out on savings that are right there in front of us.”

The groups’ analysis finds that increasing the efficiency of EVs could cut energy consumption per mile in half by 2050 — and in so doing, reduce pressure on the grid by about half.

For decades, vehicles have been getting more efficient. But EVs change the calculus. Electric cars start with a huge advantage: They don’t create waste heat. In a gas car, only 16 to 25 % of the fuel energy actually goes into the wheels — the rest is lost mostly in the form of heat and friction. In an electric car, on the other hand, 87% to 91% of the energy in the battery goes to power its wheels.

That’s why electric cars start with staggeringly high miles “per gallon,” in some cases more than 100 miles per gallon equivalent.

Sandy Munro, an automotive engineer and the founder of the consulting firm Munro and Associates, says that EVs have the potential to make greater efficiency gains, but internal combustion engines do not. “We’ve wrung out the ICE vehicle as far as it can go,” he said.

Munro helped develop the gasoline Vulcan V6 engine, which, he says, dramatically lowered engine costs — but the engine is now basically obsolete.

“Now, it’s a boat anchor,” he said. “If I had one, I’d just throw it overboard.”

But even among EVs, there can be big variability in efficiency.

In the new report, researchers found that a combination of increasing battery density, reducing tire rolling resistance, and cutting the weight of vehicles through high-strength steel or carbon fiber could double efficiency by 2050. As a guide, the study authors looked at the Mercedes EQXX, a concept car that recently drove the 627 miles from Riyadh, Saudi Arabia, to Dubai on a single charge.

The study modeled those improvements for passenger cars, SUVs and pickup trucks. The result, they projected, could be vehicles that got the equivalent of 277 miles per gallon by 2050, or over 8 miles per kilowatt-hour. If those efficiency leaps happen, they could save $200 billion annually in electricity costs by 2050 and save more than 1,000 terawatt-hours in electricity demand, the researchers projected.

“If we want electric vehicles to succeed, if we can reduce the burden on the grid — that would be hugely beneficial,” said Marc Wiseman, the founder of Oberon Insights and a report co-author.