Choosing a transformer

## Rating Start from maximum demand, add growth, and keep loading under about 80%. Pick the next standard rating. ## Type Oil-filled transformers suit outdoor substations; cast-resin dry type is preferred inside buildings. ## Efficiency A cheaper transformer with higher losses can cost much more over 15 years. Compare offers on total owning cost: price plus the cost of no-load and load losses over its life. Our transformer losses tool does this for you.