Man, i have the exactly same problem! When i meditate on my own, i get so tired afterwards. I find it helps to meditate in a group with a good teacher

When I studied at school there was our chemistry teacher. And in one of the lessons she related about her meditation experience. She did it only one time and after the process of meditation she was exhausted. All day long she could not do anything else except taking a rest after meditation) She explained it by saying that likely she had meditated wrong. She could not manage with the stream of energy flowed through her body and that's why after meditation she was frazzled:) She told that if you want to meditate you should have a skill to do it correctly. Otherwise you'll end up like her)