The 30-year fixed interest rates fluctuated between 3% and 5% since 2012. As of late, rates have increased slightly and it would be a guess to try to predict rates in the future.
Here is the cost over 30 years for a few sample rates:
Home Value:  $400,000
3.5%                $246,600
4%                   $287,478
4.5%                $329,627
5%                   $373,023
As you can see, you can add 10% for every 1/2 percentage point of interest paid.
AND, for those who can afford a higher payment, a 15-year mortgage term will save you a ton of money.
For the same $400,000 house, you’d pay in total interest:
3.0%                $97,219
3.5%                   $114,715
4.0%                 $132,575
4.5%                   $150,795