Concept:
Kirchhoff's Voltage Law states that the algebraic sum of voltages around any closed loop is zero.
Step 1: In a closed electrical loop, energy supplied by sources is equal to energy consumed by circuit elements.
Step 2: Hence, the sum of voltage rises and voltage drops in a closed loop must be zero.
\[
\sum V=0
\]
Step 3: This follows from conservation of energy.
Therefore, Kirchhoff's voltage law is based on:
\[
\boxed{\text{Conservation of energy}}
\]