Air & Water, Hayneedle and Amazon.com sell inserts for electric heaters, as of 2015. These three online retailers offer universal inserts that fit a variety of heater models. All three offer free shipping on many in-stock items.
Air & Water makes it easy for customers to find the right heater inserts with user ratings and question-and-answer sections available on each product page. Hayneedle shoppers can quickly view list prices as well as discounted rates to gauge their savings. Shoppers who turn to Amazon.com benefit from a competitive online marketplace that offers both new and used products, giving customers an opportunity to save even more on electric heater inserts.