How a Utility Evaluates Transformer Losses: Loss-Capitalisation in Practice
A worked view of how no-load and load loss are valued over the life of a transformer and turned into a tender evaluation.
A tender rarely compares transformers on price alone. Utilities capitalise losses — convert the lifetime energy cost of no-load and load loss into a present value added to the bid price.
No-load loss is the dominant lifetime cost on a lightly-loaded or distribution transformer, because it is present whenever the unit is energised. Load loss, quadratic in load, dominates where a unit runs heavily loaded.
The capitalisation rates A (for no-load loss) and B (for load loss), expressed in currency per watt, come from the utility's cost of energy, the load factor and the discount rate. A rule of thumb for a high-load-factor transmission unit: the capitalised loss cost can be of the same order as the purchase price.
The designer's response is a trade-off: spend on better core steel and lower flux density to cut no-load loss, or on more conductor to cut load loss, until the marginal cost of a further loss reduction equals its capitalised value.
The balance shifts with the evaluation. A utility with expensive energy and a high load factor will pay a premium for a low-loss design; a utility that values first cost over lifetime energy will not. This is precisely why the same transformer is rarely optimal for two different buyers.
Related principle
Transformer losses and tender evaluation (see the Masterclass chapters on losses/efficiency and procurement).