Is it necessary to replace all transformers by high efficiency ones?

Over the past decades, losses in transformers have continued to decrease. Old transformers therefore have relatively high losses. In some cases, it may be worthwhile to consider to replace these older transformers. The cost for purchasing these new transformers needs to be recovered through electricity savings. When replacing existing transformers by high efficiency models, you need to verify whether the additional volume or weight of transformers will not cause problems.