Future quantum computers have the potential to break traditional cryptographic methods that create challenges for the security of IoT devices. At the same time, a large part of IoT systems are resource-limited and will have difficulty if the requirements for better performance and computing power increase. Post-quantum cryptography is therefore becoming a more relevant research area where security must be balanced against the limitations of the system. This study compares classical and post-quantum cryptographic algorithms in terms of how they affect system performance when executed on a Raspberry Pi device. Four algorithms were compared: RSA, ECDH, CRYSTALS-Kyber and NTRU based on key generation and key exchange where execution time and memory usage were measured. The results provide a more nuanced picture of post-quantum cryptography in IoT environments. Previous research has tended to generalize resource requirements, but the results obtained in this study show that different resources are affected to different extents. Future optimizations may therefore need to focus on reducing execution time rather than memory usage. At the same time, the study shows that the transition to post-quantum methods involves a trade-off between long-term security and system performance, and during this transition phase, different solutions can be introduced in different sectors.