A survey of more than 2,000 people for the charity highlighted common risks.
It suggested people used faulty plugs or sockets and tried to mend devices which were still plugged in.
Each week on average, at least one person dies from household electrical accidents, and annually 350,000 people are injured, the ESC said.
The warning comes as the ESC launches a free smartphone app to raise awareness.
"Even though we are using more electrical products than ever before, there is a worrying gap between the public's perception of electrical danger and the reality, with people making simple yet potentially fatal errors that can be easily prevented," said ESC director general Phil Buckle.
ESC research shows that 49 of accidental house fires are caused by electricity, despite 88 of the population owning smoke alarms.
On the basis of the survey's findings, the ESC estimates that more 12 million people a year in the UK could be knowingly using faulty plugs or sockets, and 1.5 million may ignore burning smells coming from an appliance or socket.
The new ESC app "can be used any time in your home," said Mr Buckle.
"It can also be used as a basic tool when viewing accommodation, whether you are planning to buy or rent. Landlords too, should find it useful, as it will allow them to review their properties to ensure tenant safety."
The app for iPhone and Android phones allows people to do a quick, visual check on a home's electrical safety. It highlights potential dangers in each room and explains how to resolve simple, non-technical problems.
Where more serious issues are flagged, people are advised to use a registered electrician.