If you participate in an employer sponsored HSA via salary reduction agreement, your employer puts money in the account for you on a pre-tax basis. You save federal and state income tax, and also 7.65% social security and medicare tax. If you deposit money directly in an HSA from your after-tax dollars, you claim a tax deduction when you file your return, which reduces your state and federal income tax by the same amount as if the money had been deducted from your paychecks pre-tax. You don't get the additional savings in social security and medicare tax. So employer participation is better, if you have that option, but a self HSA is still a really good deal.
