The loss factor is the ratio between the average power losses (energy losses) and the losses during peak load in a period of time. In other words, the loss factor is simply the load factor of the losses. There are two methods to calculate the loss factor:

Neher McGrath / Dorison

For the Neher McGrath / Dorison method, the power and energy losses are not obtained from directy measurements. Their estimations are based on previous knowledge of their own loss factors. The loads present nearly constant power factor, and express both the demand and energy in p.u. of their respective maximum values. Thus, the loss factor can be expressed in relation to the demand. The consumer diversity and the different consumer behaviours in areas with different geographical and socioeconomic characteristics has an influence on the loss factor. The loss factor could be optained by using the load curves of all customes which is not viable. Based on measurement campaigns, characteristic curves for consumers separated by groups (e.g. tariff groups) are obtained. The technical losses in the systems can be divided in two large groups: independent (constant) losses of the load like losses in the transformer cores with with μ = 1 and the depended (variable) losses of the load such as ohmic losses with μ < 1. All the studies in the search for a relationship between the loss and the load factor led to the same empiric equation below (first equation).

Symbol
$\mu$
Unit
p.u.
Formulae
$LF^{2} \left(- k_{\mathrm{LF}} + 1\right) + LF k_{\mathrm{LF}}$
Related
$k_{\mathrm{LF}}$
$LF$
$\mu_{\mathrm{w}}$
$\mu_{\mathrm{y}}$
Used in
$T_{\mathrm{4\mu}}$