De or het stoelverwarming?

The correct Dutch article is:

de stoelverwarming

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

How to use stoelverwarming

the stoelverwarmingde stoelverwarming
this stoelverwarmingdeze stoelverwarming
that stoelverwarmingdie stoelverwarming
our stoelverwarmingonze stoelverwarming
your stoelverwarmingjouw stoelverwarming
every stoelverwarmingelke stoelverwarming
which stoelverwarming?welke stoelverwarming?
a big stoelverwarming / the big stoelverwarmingeen grote stoelverwarming, de grote stoelverwarming