Euro SIM cards

Your best option is Google Fi, which works globally. You pay for usage and can freeze service when you want to. The only catch is that you must activate service before you depart.

A SIM from one EU country will work across the bloc without roaming fees. It’ll be well cheaper than using US- based Google Fi.

I hate to be this guy, but do you have visa issues sorted? It’s usually challenging to travel multiple Schengen countries for that length of time.

Scudder, I am glad it was you who asked because I was wondering the same thing. Generally, spending that much time in Europe requires a base country, and straying from that base is still 90/180 limiting. A consideration because mobile service from the base country should suffice for traveling throughout Europe and that is from where you would purchase service. It would be possible to add travel to the UK, but again, one service provider would largely suffice.

I am not clear on the OPs overall requirements. Is it data, voice, or a combination?

We need more information.

Europe is a big place. Only part of it is within the EU, and generally free roaming is only within the EU, and vestigially the UK for some.

Unless you have a long term visa you will need to be outside the EU for at least 90 days in every 180 so you will need local cards for that.

I see in your profile that you have down that you are "moving to Europe for a year". Could you clarify where that will be - the rules vary.

A touch more info from you will result in dramatically more accurate replies.

Read the Google Fi TOS carefully before you sign up. If you're going to be overseas for an entire year, I don't think it's for you.

Thanks for the replies. We won't be based anywhere. We are aware of the 90/180 issue. We plan on leaving the zone as needed, going to the UK and other nonzone nations. Does that change any advice? Will we need different SIM cards in and out of the zone?

We have a vodafone SIM card with a UK phone number that we use when traveling. We bought it a few years ago online and activated
it with our first use in Europe. The card works in most European countries. Before a trip we buy a bundle of unlimited calls and texts with 500 mb (I think) of data for 30 days. We are able to do this online. This costs 10 pounds, about $13 when we bought it last month. Since we mostly use wifi in our lodging, the data is enough but there are larger bundles if needed. We do have to keep the card active by using it to send a text every six months or so.
We find this to be a good solution to the SIM card/phone company issues we previously encountered. Thanks to CWSocial for suggesting this to us!

We plan on leaving the zone as needed, going to the UK and other
nonzone nations. Does that change any advice? Will we need different
SIM cards in and out of the zone?

That might change the advice a bit. The EU has abolished roaming charges so a Greek sim card will work in Denmark without any additional charges and so on. But if you travel outside the EU there you might be charged extra, and using sim cards from non-EU countries might be expensive if you leave the country.

The 90/180 rule applies to the Schengen area and you need to know the difference between the EU and the Schengen area. Most EU countries are Schengen members, but some are not. And in addition some non-EU countries are part of Schengen.