Abstract
In the article, economic estimation is given for the measures on purchase of new power transformers and replacement of the existing ones for the Latvian power system (Latvenergo). The optimal choice for the purchases and deliveries of new power transformers is considered as a task of choosing among suppliers on a competitive basis (through tenders). As the objective function for the estimation, the total annual discounted costs for the user of a transformer during its service life are taken. A simplified estimation model is proposed, based on which the calculations of tenders have been done.