I asked a friend of mine who has used Google Wallet to tap and pay; but, he has always had mobile service when he has done it. I called Google Wallet support; it took the guy a while to search for an answer while I was on hold. He seemed to think that I do need a network connection.
Forums and other articles seem split on the question.
Why Ask Now?
For many reasons, I was not able to make use of the service since it launched. I ordered the Google Wallet card as soon as I was able to access the form. Prior to that, I activated the payment service via Gmail. I was not able to use those two services, nor the tap and pay service, because I had no money in my account or did not have the technology to support it.
Recently, I poked around my pay cards, as I have not had a checking or savings account for years, and discovered that I could use them for electronic funds transfers, both in and out, like a checking account would do. Most prepaid cards only accept direct deposit, and reject drafts. So, due to a change in employment, in which I would have had to change direct deposit anyway, I finally linked a monied account to my Google Wallet.
Now that I am able to fund my Wallet account, I am curious if I need a network connection. This isn't mere curiosity. I have Nexus 7 tablet I mentioned, and a phone that doesn't do NFC. So, there is a practical reason. I am also more likely to be holding a tablet in line at checkout than my Google Wallet card.
Why It Should WorkUsing my thinking skills, I imagine paying using Google Wallet tap and pay should work without an Internet connection because tap and pay credit cards work that way. My conjecture is that Wallet syncs once per day to update its NFC code for the day and stores it locally.
Why It Should Not Work
Because it would be too logical.
What I Am Going To Do
Tomorrow morning, before leaving home, I will launch my Google Wallet app so that it can sync. Then, on the way to work, I will stop somewhere that supports tap and pay to test the feature. To be certain that I don't accidentally hop onto some runaway hotspot, I'll turn off the Wi-Fi radio beforehand.
I'll either be pleased with the result or look like a dork. But, I shall no longer be an ignorant dork.
I'll let you know how it works out.