De or het rentebesparing?

The correct Dutch article is:

de rentebesparing

Rule Words ending in -ing: almost always de. See the rule

How to use rentebesparing

the rentebesparingde rentebesparing
this rentebesparingdeze rentebesparing
that rentebesparingdie rentebesparing
our rentebesparingonze rentebesparing
your rentebesparingjouw rentebesparing
every rentebesparingelke rentebesparing
which rentebesparing?welke rentebesparing?
a big rentebesparing / the big rentebesparingeen grote rentebesparing, de grote rentebesparing