A transformer runs for thirty years or more and loses energy in every hour of them, so the purchase price is only part of what it costs you. Loss capitalisation puts a euro value on each watt of no-load and load loss, which lets you compare competing offers on lifetime cost instead of sticker price. In most continuously energised applications, the more efficient unit repays its premium well before the end of its life.
Which losses actually cost you money?
No-load loss occurs in the core whenever the transformer is energised, loaded or not. It runs 8,760 hours a year and is essentially constant. Load loss occurs in the windings and rises with the square of the load current, so a unit at half load produces a quarter of its rated load loss.
That split decides which unit is cheaper for you, not which is cheaper in general. A distribution transformer energised continuously but averaging 25 % load is dominated by no-load loss. A furnace or process transformer running near rated load through the shift is dominated by load loss. Match the loss profile to the duty you actually have, not to a datasheet comparison at 100 % load.
How does loss capitalisation work?
The method assigns a capitalisation factor A to no-load loss and a factor B to load loss, both in euro per watt, derived from your electricity price, expected load factor, service life and discount rate. The evaluated cost is then the purchase price plus A multiplied by the no-load loss plus B multiplied by the load loss. The offer with the lowest evaluated cost wins — often not the lowest quote.
Set A and B honestly: optimistic load factors and low energy prices flatter the cheap unit and hide the running cost. Publishing your factors in the enquiry also makes every bidder optimise the design against the same target.
A worked example
Assume — purely as an illustration, and not as Protrafo pricing — a 1,000 kVA distribution transformer energised 8,760 h per year at an electricity price of €0.15/kWh, with an average load factor of 30 % and a 30-year life, undiscounted.
- Unit A: no-load loss 1,100 W, load loss 10,500 W at rated load.
- Unit B: no-load loss 770 W, load loss 9,000 W at rated load.
- No-load energy per year: 9,636 kWh against 6,745 kWh — a saving of roughly 2,891 kWh, or €434.
- Load energy at 30 % load, where losses scale with the square of the load: 8,278 kWh against 7,096 kWh — a further 1,182 kWh, or €177.
Together that is about €611 per year, or roughly €18,000 undiscounted over 30 years. If unit B costs €4,000 more to buy, it repays the difference in under seven years and returns several times that over its life. Move the load factor to 60 % and load losses take over; move the energy price to €0.25/kWh and the payback almost halves. Run the arithmetic with your own figures; the answer is sensitive to all three.
What else belongs in the total?
Losses are the largest running cost but not the only one. Include installation and civil works — an oil-immersed unit needs a bund, a cast resin unit indoors may need a larger ventilated room — along with maintenance intervals, oil sampling and dissolved gas analysis, spare-part and repair availability, and the cost of unplanned downtime.
Reliability is hard to price and easy to underestimate. Condition monitoring of oil and winding temperature, tank pressure and power quality moves failures from unplanned to planned; Protrafo Insights does that and extends the standard two-year warranty to five years — a genuine line in the total cost.
Is EcoDesign Tier 2 enough?
Tier 2 (Regulation 548/2014, mandatory since July 2021) is the legal minimum, so every compliant new unit already has respectable losses. The real question is whether to go beyond it. For a continuously energised transformer with a long expected life and a rising energy price, an amorphous core or a lower-flux design usually pays back. For a standby unit energised a few hundred hours a year, it usually does not.
The practical rule: never compare quotes without capitalising losses, and always state your own A and B factors in the enquiry so every supplier designs against the same target. If you remember one thing, remember that no-load loss runs 8,760 hours a year regardless of what the site is doing. That is where the cheapest transformer quietly becomes the most expensive one.
