What security level do I actually need for a home shredder?

For most households, a P-4 cross-cut shredder is the consensus floor — it cuts paper into confetti-sized pieces that meet the level recommended for confidential financial and medical documents. P-5 micro-cut goes further (smaller particles, harder to reconstruct) and is what reviewers steer privacy-conscious buyers toward. P-3 strip-cut machines are widely criticized as inadequate for anything with personal data.