You have to follow the steps required in section 101(c) of the ESIGN Act. One of the requirements is that the consumer must
consent electronically, in a manner that reasonably
demonstrates that the consumer can access information
in the electronic form that will be used to provide
the information that is the subject of the consent; ....
That's what's meant by "demonstrable consent." You can't assume that the consumer is able to view statements just because he or she can access your homebanker system. And viewing account history on homebanker isn't the same as viewing (and being able to retain) account statements. If the statements are in pdf format, how will you know the consumer can open, read and save pdf files?
Having your customer include a "passcode" from the sample statement in the customer's consent for receipt of electronic statements is one way to demonstrate that the consumer can get, open and save those statements.
While you're in the neighborhood (the ESIGN neighborhood), consider including within the list of disclosures you'll ask for consent to receive electronically any of the other disclosures the you might want to deliver this way. Think about "subsequent disclosure requirements" in each of the applicable regulations -- E, CC, DD -- and things like error resolution notices, etc.