(1) For the purposes of this rule, the following definitions shall apply:
    (a) Category or Category of Depreciable Plant – A grouping of plant for which a depreciation rate is prescribed. At a minimum it shall include each plant account prescribed in subsection 25-6.014(1), F.A.C.
    (b) Embedded Vintage – A vintage of plant in service as of the date of study or implementation of proposed rates.
    (c) Mortality Data – Historical data by study category showing plant balances, additions, adjustments and retirements, used in analyses for life indications or calculations of realized life. This is aged data in accord with the following:
    1. The number of plant items or equivalent units (usually expressed in dollars) added each calendar year.
    2. The number of plant items retired (usually expressed in dollars) each year and the distribution by years of placing of such retirements.
    3. The net increase or decrease resulting from purchases, sales or adjustments and the distribution by years of placing of such amounts.
    4. The number that remains in service (usually expressed in dollars) at the end of each year and the distribution by years of placing of such amounts.
    (d) Net Book Value – The book cost of an asset or group of assets minus the accumulated depreciation or amortization reserve associated with those assets.
    (e) Remaining Life Technique – The method of calculating a depreciation rate based on the unrecovered plant balance, the average future net salvage, and the average remaining life. The formula is:
100% – Reserve % – Average Future Net Salvage %
Remaining Life Rate