A baseload price is the average price to supply baseload devices (i.e. devices that run constantly) with energy over a year.
The baseload price is a relevant concept for time-of-use plans where the price of energy changes over time yet some of your devices run constantly through all of those price periods. We sometimes display this average in our fine print for time-of-use electrical plans, but do not display it for single rate plans as there can be no average price when there is only one price.