@rapropos do you mean the code itself in the bundles.js (= app size) or the translations data them self?
When it goes to the translations data, according the doc, per default, they will be shared across modules
Lazy loaded modules
When you lazy load a module, you should use the forChild static method to import the TranslateModule.
Since lazy loaded modules use a different injector from the rest of your application, you can configure them separately with a different loader/parser/missing translations handler. You can also isolate the service by using isolate: true. In which case the service is a completely isolated instance (for translations, current lang, events, …). Otherwise, by default, it will share its data with other instances of the service (but you can still use a different loader/parser/handler even if you don’t isolate the service).