Correct spelling and/or hyphenation for electronic commerce

What is the correct spelling and/or hyphenation for the abbreviation of electronic commerce?

I have seen the following variations.

  • eCommerce
  • E-Commerce
  • ECommerce
  • E-commerce

According to this Google Ngram, both E-Commerce and E-commerce are valid and interchangeable: enter image description here

Likewise, when not beginning a sentence (or in a headline, etc.), the term e-commerce is not capitalized:

e-commerce |ˈēˌkämərs|:

(noun) commercial transactions conducted electronically on the Internet.

See what happens when e-commerce is added to the Ngram.

According to Wikipedia, eCommerce is a viable, though less often used alternative. The Ngram supports that assertion. The only variation which is completely incorrect is ECommerce.

Definition from: New Oxford American Dictionary

Conclusion:

  • E-Commerce is almost always hyphenated. The only non-hyphenated alternative is eCommerce.
  • Furthermore, e-commerce is not capitalized unless one begins a sentence with it, or uses it in a headline/title.
  • When capitalized, both E-commerce and E-Commerce are correct, though I prefer the latter.