LOLP and LOLE

LOLP (Loss of Load Probability) is the probability that generation will be insufficient to meet demand at some point over some specific time window. Check out http://www.nwcouncil.org/energy/powersupply/presentation1999_1208/sld013.htm.

LOLE (Loss of Load Expectation) is a measure of how long, on average, the
available capacity is likely to fall short of the demand. LOLE is a statistical measure
of the likelihood of failure and does not quantify the extent to which supply fails to
meet demand. LOLE is the expected number of days in the year when the daily peak demand exceeds the available generating capacity. It is obtained by calculating the probability of daily peak demand exceeding the available capacity for each day and adding these probabilities for all the days in the year. The index is referred to as Hourly Loss-of-Load-Expectation if hourly demands are used in the calculations instead of daily peak demands. LOLE also is commonly referred to as Loss-of-Load-Probability.