Ebac in Newton Aycliffe expects to make up to 300,000 washing machines a year once it is fully operational.
The family-run company, which also makes dehumidifiers and water coolers, was awarded from the government's Regional Growth Fund for the project.
The production line is being officially opened by the Duke of Kent later.
Currently, the three million washing machines purchased annually in the UK come from overseas.
John Elliott, chairman of Ebac, said: "It is so important that UK manufacturing receives support and recognition for the vital role it plays in the economy."
Washing machine manufacturing is set to return to the UK after a gap of almost 10 years with the opening of a new factory in County Durham.