Asked about the timing of E.ON's price rises announcement, which came amid media focus on the death of Nelson Mandela and the devastating storms across the UK, Downing Street said, "It is for them to explain their decisions."
Energy firm E.ON said it does not expect to have to raise prices in the next 18 months "as a result of social or environment obligations".
E.ON said in a statement that the Government's energy announcement "should mean our customers pay less next year".
"There remains a risk, however, that increases in network charges or wholesale energy costs for example could force a price increase", it said in a statement, adding, "But the company very much hopes that situation does not occur".
Tens of thousands of pensioners will face a hike in energy prices after E.ON withdrew its discount tariff for over-60s.
The StayWarm deal, which offered fixed-price energy for older customers based on their average consumption levels, will come to an end from 7 October.
The energy firm says the move has been forced by changes to the number of tariffs permitted by regulator Ofgem.
A spokesman said: "We are writing to all customers as their contracts come to an end, and where possible we are also contacting them by phone with the aim of speaking to each customer to help ensure they switch to the best product for their needs."
Customers with one of the "Big Six" suppliers will soon be able to compare their energy use with that of their neighbours in a bid to reduce their household bills.
E.ON has teamed up with US company Opower, which works with utilities to save consumers money, to launch an online 'saving energy toolkit' to help them understand their energy use.
Consumers will see their electricity and/or gas use compared with 100 anonymous E.ON customers with homes of a similar size and type, and against the most energy efficient homes in their local area.
The scheme gives households a breakdown of where and when energy is used in the home, including a "what uses most" chart that splits current usage into heating, lighting, hot water, appliances and other use.
It will also detail how energy use changes from month to month, and compare costs for the current month to the previous month, showing how bills have been affected by weather and usage.