The government estimates that 250 megawatts of power per day can be saved by having more daylight hours in the evening so that people can avoid using electric lights, junior Power and Energy Minister Shamsul Haq Tuku said.
The country is struggling with a shortfall of more than 1,000 megawatts per day.
People are supposed to shift clocks forward by an hour at midnight June 19 and leave them that way until October.
However, there are doubts about compliance in a country where nearly half the people are illiterate.
"People here are not easy to change to a new lifestyle," said Hamidur Rahman, a school teacher in Dhaka. "It may prove difficult to make people to observe the new system."
The government said it is using television ads and distributing handbills across the country to encourage people to switch to the new time.
Power shortages have become severe in impoverished Bangladesh even though only 45 percent of its 150 million people have access to electricity. The country produces about 3,800 megawatts of electricity a day, compared to a demand for about 5,000.
Frequent outages have prompted industries, shops and households to install their own generators, pushing up the cost of living.