In this paper, we discuss the high stability of a single-phase hybrid polyelectrolyte (SPHP) and nanocomposite hybrid polyelectrolyte (NHP) in a large electrochromic (EC) device (5 cm × 10 cm) mounted with different electrodes. The electrochromic device (K-glass/FTO/WO
3
/SPHP/CeO
2
-TiO
2
/FTO/K-glass—ECI,K-glass/FTO/WO
3
/NHP/CeO
2
-TiO
2
/FTO/K-glass—ECII,) exhibited excellent color and bleach reversibility, high coloration efficiency (CE) (35 cm
2
/C) from the first cycle up to more than 60,000 CA cycles, and a maximum constant rate of deintercalation/intercalation (O
out
/Q
in
= 1). Also, the life time of the EC device with Nb
2
O
5
:Mo (K-glass/FTO/Nb
2
O
5
:O/SPHP/CeO
2
-TiO
2
/FTO/K-glass—ECIII) was prolonged to up to more than 10,000 cycles with a fairly stable coloration efficiency (around 19 cm
2
/C) and O
out
/Q
in
= 1. The SPHP and NHP were tested in a large EC device with different configurations to evaluate its successful performance. In conclusion, its remarkable behavior and high stability render this material an excellent candidate for application in EC devices.