How to Determine the KVA of a Transformer for a Home

Transformers connect the power from the ultitity company to the home.

Transformers are used in the home to convert input voltage from the utility company to the voltage required to run the electrical appliances in the home. A transformer consists of primary and secondary windings. Utility company power is fed to the primary side of the transformer, then it is stepped down or up depending on needs of the home. KVA, which stands for kilovolt-amperes, is the power rating of the transformer.

Instructions

1. Find the input voltage requirements for the electrical appliances in the home. Typically, this is 120 volts, assuming standard home electrical outlets.

2. Find the highest current usage in the home. Go to the circuit breaker panel. Review all of the circuit breakers in the panel. Find the breaker with the highest amperage rating and write it down. Each breaker has the amperage on the front cover. For example, assume that it is 30 amps.

3. Calculate the transformer KVA requirements by multiplying the voltage from Step 1 by the current from Step 2, then dividing by 1000. Continuing with the example numbers: Transformer KVA = (120 x 30)/1000 = 3600/1000 = 3.6 KVA.

References

• Jemelec: How to Specify Your Transformer