In addition to the obvious point mentioned in a sibling comment (existential threat to humanity)...

Switching to zero-emissions alternatives now means less adjustment later when the polluting versions are (hopefully inevitably) banned.

When they are banned however there will likely be incentives, cheaper prices and better technology. Switching now makes even less sense.

Tragedy of the commons right there.

Granting your premise, it's still not a problem upon which individual actions like this have any impact whatsoever. What OP does with his house, heating it with gas, electric, wood, or coal is not going to matter one bit on a global scale.

There are almost zero people on the entire planet whose personal impact is noticeable at this scale. But so what? We need both individual and policy action.

“At scale, nobody notices the harm I’m doing” can be used to justify all manner of antisocial behavior. I don’t buy the argument.

Existential? As in humans go extinct? I’m going to have to ask for a source.