You're going on Erasmus for several months, and the question is always the same: how to have mobile internet from day one without breaking the bank or losing your home number. The short answer is a data eSIM that coexists with your Spanish SIM card: you keep your line for banks and WhatsApp, and you browse with cheap local data. In this guide, I'll tell you how to set it up properly for a whole semester.
What is an eSIM and why is it perfect for Erasmus
An eSIM for Erasmus is a digital data plan that you install on your mobile without a physical card: you browse with the local network of the destination country for weeks or months, and your Spanish SIM remains inside for calls and SMS. It's the cleanest way to have stable internet as soon as you land.
Compared to buying a prepaid SIM in the country (queues, paperwork, sometimes requiring a residence permit) or paying daily roaming, an eSIM is activated from your sofa. You install it before you leave, scan a QR code, and when you arrive, it connects automatically. For a student who will be abroad for a whole semester or the entire academic year, this saves real time and money. With more than 218 destinations covered, it doesn't matter if your Erasmus is in Italy, Germany, Poland, or Portugal: there's a plan for your city. If you want the step-by-step technical details, you have the specific eSIM guide for Erasmus students with screenshots.
Keeping your Spanish number while studying abroad
Yes, you can keep your Spanish number intact. The eSIM only provides data; your Spanish SIM card remains installed and active for receiving bank SMS, verification codes, and calls from home. On your phone, you choose which line uses data (the eSIM) and which line handles calls and messages (your usual SIM).
This is crucial during Erasmus: for months, you'll need your number for your banking app, for Bizum, for university two-factor verification, and for your family to call you without dialing strange prefixes. Leave your Spanish SIM in "calls and SMS only" mode to avoid data roaming charges, and set the eSIM as your default data line. This way, you browse cheaply but remain reachable on your usual number. You can find the details in the guide on how to keep your Spanish number with an eSIM.
Tip: before you leave, disable data roaming for your Spanish SIM card in Settings. This way, only the eSIM will use data, and you'll avoid surprise charges from a video loading in the background.
How much data an Erasmus month consumes
An Erasmus student uses more data than a tourist: daily maps, online classes, video calls home, series at the apartment, and a lot of WhatsApp. Here are approximate monthly figures to help you calculate your plan without overspending or running out.
| Student Profile | Approx. Monthly Usage | Recommended Plan |
|---|---|---|
| Economical (lots of university and apartment Wi-Fi) | 3-5 GB | Small, rechargeable monthly plan |
| Medium (maps, social media, some video outside home) | 8-12 GB | Standard monthly plan |
| Intensive (streaming and video calls using mobile data) | 15-20 GB or more | Large plan or abundant data |
The advantage of an eSIM is that you can top up on the go without changing cards: if you run short one month, you can add gigabytes from the app. For long stays, there are also Europe eSIM plans for a full month that offer better value than combining individual weeks.
Long-stay eSIM vs. your operator's roaming
Many Spanish operators include EU roaming, but with small print: there's a limit on roaming gigabytes, and exceeding it incurs an extra charge per GB that can be very high. For a weekend, it doesn't matter; for an Erasmus of four or five months, that cap is quickly exhausted.
- Operator Roaming: convenient at first, but with a data limit in the EU and high costs if you exceed it. Outside the EU (e.g., an Erasmus in the UK or Turkey), it becomes much more expensive, sometimes €10-20 per day.
- Long-stay eSIM: plan designed for weeks or months, with abundant data and top-up options. Fixed price, no surprise bills.
If your destination is outside the EU, the eSIM stops being an option and becomes almost mandatory to avoid financial ruin. And even if it's within the EU, having a separate plan frees up your Spanish tariff's allowance. For backpackers and students who travel a lot, check out the cheap eSIM for backpackers in Europe.
How to activate it before flying
The classic mistake is leaving the eSIM for the destination airport without Wi-Fi. Do the opposite: install it at home with your Wi-Fi a few days beforehand. Installation takes about 1 minute and you only need to scan a QR code.
- Purchase the plan for your Erasmus country and receive the QR code instantly via email.
- With Wi-Fi at home, go to Settings and add the eSIM by scanning the QR code.
- Label it as "Data" and keep your Spanish SIM as "Primary" for calls.
- Activate eSIM data usage only when you land; until then, use Wi-Fi.
First, check if your phone is eSIM compatible (almost all recent models are). If you get confused with the installation, the guide on how to activate an eSIM explains it with screenshots for iPhone and Android.
Tips to stretch your data throughout the semester
An Erasmus semester spans many months, so optimizing data makes the difference between topping up little or paying extra. These habits will extend your plan without you feeling like you're "skimping" on connection.
- Download offline maps of your city and your weekend trip destinations.
- Download series and music using your home or library Wi-Fi to watch them later without data.
- Limit auto-play video on Instagram, TikTok, and YouTube.
- Check which apps consume the most data in Settings and cut off their background data.
- Use your phone as a hotspot only when necessary, not continuously.
And if you travel to other countries on weekends from your Erasmus city, don't buy a new eSIM for every short getaway: consider an eSIM plan for Interrail in Europe or a regional one that covers several countries at once.
Frequently asked questions
Can I use the same eSIM for the entire Erasmus semester?
Yes. You buy a long-stay plan for your destination country and top it up when you run out of gigabytes, without changing cards or QR codes. Many students start with a monthly plan and add data depending on whether they have a month with more video streaming or travel.
Do I lose my Spanish number if I get an eSIM?
No. The eSIM only provides data, and your Spanish card remains installed and active for calls and SMS. You keep your number for the bank, Bizum, and your family. You only need to disable data roaming on the Spanish SIM to avoid accidentally incurring roaming charges.
Does the eSIM work if my Erasmus is outside the EU?
Yes, and that's where you save the most. In destinations outside the European Union, your operator's roaming charges skyrocket, whereas a local eSIM for the country gives you data at a fixed price. Coverage is available in more than 218 destinations, both within and outside Europe.
How many gigabytes do I need per month during Erasmus?
It depends on your usage, but an average student uses between 8 and 12 GB per month when using mobile data outside the home. If you have good Wi-Fi at your apartment and university, 3-5 GB might be enough. For constant streaming and video calls, estimate 15-20 GB or more.
When should I install the eSIM, before or upon arrival?
Install it at home with Wi-Fi a few days before you fly; installation takes about 1 minute. Then activate data usage only when you land. This way, you arrive with everything ready and don't depend on finding Wi-Fi at an unfamiliar airport.
Conclusion
A well-connected Erasmus starts with the basics: cheap local data from day one and your Spanish number intact for everything important. A long-stay eSIM gives you both without queues, without paperwork, and with top-ups when you need them. Install it before you fly and land already connected to focus on what matters: enjoying your semester abroad.
