This may be the answer to your question: http://support.screeps.com/hc/en-us/articles/204332302-Understanding-CPU-limit-usage As far as I understood your post, there seems to be nothing wrong with the CPU management.You may use up to 500 CPU depending on how much you saved up. If the bucket is depleting, this limit is lower. If the bucket is completely empty, your CPU limit is actually your account limit (35).