The two million letters - up from the one million promised when Malcolm Turnbull met big power retailers earlier in the month - will arrive in letter boxes before Christmas.
They'll direct customers on so-called standing offers to the government's comparison website, Energy Made Easy, where they can discover better deals.
About half of all households haven't changed retailers or contracts in the past five years and about a million people are stuck on the more expensive standing offers.
"People's unwillingness to change is helping the retailers," the Prime Minister said on Channel Nine's A Current Affair program.
When pressed on whether there should be one single regulated rate for electricity, Mr Turnbull said no.
"I think if you have one regulated rate then you eliminate the opportunity for competition so it's important to make sure that there is competition in the market so people will get cheaper prices.
"Competition is not driving up prices, there are a number of other factors, one of those is gas prices."
Earlier, Mr Turnbull told reporters in Sydney that households could save hundreds of dollars a year by switching plans.
"This is a very big breakthrough, and it's happening here and now," he said.
Retailers also agreed to put a barcode on bills which customers can scan and use to search the comparison website with their usage and payment data, similar to a UK scheme.
There will also be new rules preventing retailers from offering deals that start with a higher base rate than the standing offer and have set-period discounts to drop below it.
And they agreed to look at whether it was feasible to switch to monthly rather than quarterly billing.
Energy Ministe Josh Frydenberg, Dep Prime Minister Barnaby Joyce, Prime Minister Malcolm Turnbull and Treasurer Scott Morrison meeting with Energy company heads Source: AAP
The sector saw the meeting as productive, with the Australian Energy Council saying electricity was a consumer good just like insurance or mobile phones and it paid to shop around.
"We agree it's important for retailers to assist customers to find the best deal, especially at a time when the cost of electricity is high," chief executive Matthew Warren said.
"The underlying problem remains though - we need policy certainty and new investment in generation in order to bring down energy costs in the long term."
Energy Minister Josh Frydenberg said there had been more than 215,000 hits on the previously little-known Energy Made Easy website since the government first hauled power companies in three weeks ago.
"Due to the actions of your government, Australian families are now alert to the big savings that they can achieve to their electricity bills by moving retailers or contracts," he said.
Labor rubbished the scale of the government's claimed achievement.
"In a display that lacked even the thin substance of his first dressing down of retailers, all the prime minister could do was plead with retailers to write a letter to customers asking them to visit a website," opposition energy spokesman Mark Butler said.
The government is expected to receive a report on Friday from the Australian Energy Market Operator on the likely gaps in baseload power into the future, which could impact on power prices and reliability.
