Packed-bed thermal energy storage (PBTES) is an affordable option to store energy in concentrated solar power (CSP) plants, where supercritical carbon dioxide (s-CO2) can be the working fluid in Brayton cycles. Due to the elevated operating pressures required by the s-CO2 in the power block, the PBTES tanks require thick walls to operate safely, representing constructive and economic constraints for their applicability. Then, this work compares two constructive alternatives from a numerical standpoint: steel-only walls and reinforced concrete (RC) walls. The comparison of these wall materials considers their thermal performance and the levelized cost of storage (LCOS) for different tank configurations, a novelty from the perspective of comparing the performance of different wall materials for PBTES tanks. A fixed volume of 2660 m3, required for 8 h discharge in a 10 MW CSP plant, is maintained. The total storage volume can be divided into one, two, four, or eight parallel tanks while considering several aspect ratio values (AR = 0.5 to 10) and wall inclinations (rp = 0 degrees, 5 degrees, and 10 degrees). The reinforced concrete walls excel in every aspect considered, and the one-tank configuration with AR = 1 and rp = 0 degrees presents the best LCOS.