About 700 watts, it makes for a decent space heater in the winter.

Like others said, self signed or internal only domains work. Really though for the minimal cost of generally less than $20/year you can make it a lot easier by just buying a domain.

From a pure security stance it could be argued that a personally owned CA is more secure than any public one since it’s possible for others to create a trusted cert with a public entity. Cloudflare ends up doing that for any domains you register with them, but that’s really only an issue for things facing the web and using self signed certs will typically cause problems for any pre-compiled client apps you might use.