De or het gasverwarming?

The correct Dutch article is:

de gasverwarming

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

How to use gasverwarming

the gasverwarmingde gasverwarming
this gasverwarmingdeze gasverwarming
that gasverwarmingdie gasverwarming
our gasverwarmingonze gasverwarming
your gasverwarmingjouw gasverwarming
every gasverwarmingelke gasverwarming
which gasverwarming?welke gasverwarming?
a big gasverwarming / the big gasverwarmingeen grote gasverwarming, de grote gasverwarming