MIDWEST’s web site has a “Transformer Calculator” to help customers decide what transformer they need for specific load. We are frequently asked by customers to help them determine what size transformer they need to replace an existing power transformer. The Transformer Calculator uses voltage, current, and Kva. If you have any two, it will calculate the third value. This allows the user to quickly see what happens if they make some changes. We had a customer ask about a Square D 50 Kva, 480 volt to 208/277 volt dry type transformer. When we discussed their load needs and diversity, they decided they needed a 75 Kva transformer instead, based on their present and expected future load. This is a common occurrence. By having access to the power transformer calculator, you can play with the numbers yourself. The usual variable is current, aka load, amps, juice. The voltage is usually a known, fixed value. So by calculating existing load and estimating future load, you can quickly estimate the size of the transformer you might need, in Kva, by using the Transformer Calculator. We also suggest having at least 20% excess capacity. Quick tools such as this should not be used for design purposes. That needs to be left up to experts.