@christine2756 I understand that the apr is an annual rate and that rate is paid on a declining balance and that as the years progress more of the payment goes to principal than interest.
That said for a €100,000 mortgage over 20 years with a rate of 0.8 the total interest paid would be €8,246 and for a rate of 2.8 the total interest paid would €30,714
Taking the above figures gives a percentage difference of 370%
The rate of 2.8 would have monthly payments of €544 and that of 0.8 monthly payments of €451.
A lot to consider when changing rates.