WASHINGTON — Improvements in energy efficiency can be achieved to slow the growth of electricity demand over the next two decades by at least 22 percent, but it will require investments of billions of dollars, says a new study.

The report released Tuesday said there are a wide range of realistic efficiency improvements that can be made so the country by 2030 would require 5 percent to 8 percent less electricity than has been projected.

But the energy savings would come at a price.

The study released Wednesday by the utility-supported Electric Power Research Institute said utilities would have to invest between $19 billion and $47 billion between now and 2030 to get the maximum power savings that realistically can be achieved.

Most of the savings would come from new building codes, tougher appliance and lighting standards and a phase-out of less efficient equipment to heat and cool buildings as well as development of a "smart" electric grid that would allow utilities to fine-tune energy use, the report says. And while much of the savings would come from residential use, the biggest will come from better commercial motors and office and factory lighting.

"We have tremendous opportunity to reduce the consumption of electricity," said Michael Howard, an EPRI vice president who presented the findings Tuesday at an energy conference.

Howard said electricity use has increased on average 2.5 percent a year over the last 35 years and has been projected to increase 1.07 percent annually up to 2030. But he said the EPRI analysis concludes the annual growth in power demand could be cut to 0.83 percent even if not everyone buys the most efficient appliances and equipment.

President-elect Barack Obama repeatedly has said a core of his energy policy will be to improve energy efficiency including tougher appliance standards.

The study does not take into account the expected increase in electricity demand from the emergence over the next two decades of more plug-in hybrid vehicles. If, as some experts expect, there are 8 million electric cars on the road by 2030, they are expected to boost power demand by 2 percent, Howard acknowledged.