UL = These products are U.L.  Underwriters Laboratory, ensuring that the products have passed Underwriters Laboratory's rigorous testing procedures for electrical products and have the listings number required for specific electrical codes.

  ETL = A product bearing the c ETL us Listed mark signifies that it was tested and meets the minimum requirements of prescribed  products safety standards for US and Canada. Moreover, the mark  indicates the manufacture's production site conforms to a range of compliance measures and is subject to periodic follow-up inspections to verify continued conformance.

 CSA = The CSA mark is recognized and accepted  through Canada and the U.S. at federal, state, provincial, and municipal levels. It means that the product is certified for the Canadian and US markets, and is certified to applicable Canadian and US Standards

So no matter which label you see on your electric heater you can be sure its safe and reliable for years to come.