Every operator markets its annual pack on the headline saving, and every comparison site repeats the number. The saving is real, but it is not the number on the banner, and understanding why changes which pack you should buy.
Start with cost per day, not the total
Jio's ₹299 pack runs 28 days, so it costs ₹10.7 a day. The ₹3,599 annual pack runs 365 days at ₹9.9 a day. That is a 7.5% saving — meaningful, but a long way from the 'two months free' framing you will see quoted.
The larger saving hides in a place the banners never mention: a 28-day pack is not a month. Twelve monthly recharges cover 336 days, not 365, so you actually buy thirteen packs a year. Counting properly, the annual pack saves closer to ₹290 on Jio and ₹1,000 on BSNL.
Where monthly still wins
- You are likely to port out. A year of locked-in validity is worthless the moment you switch networks, and operators do not refund unused validity.
- Your usage is about to change. Moving cities, starting a job with a work SIM, or switching to broadband at home all shift how much mobile data you need.
- The upfront amount matters more than the rate. ₹3,599 in one payment against ₹299 a month is a real cash-flow difference, and paying it on a credit card you then carry a balance on wipes out the entire saving several times over.
The one that actually pays
BSNL's ₹2,399 annual pack at 2GB/day works out to ₹6.6 a day — around ₹1,200 less over a year than the equivalent private-network annual pack. If the network covers where you actually live and work, that is the single largest recurring saving available in this entire category, and it does not depend on catching an offer at the right moment.
Check the price history on any pack before committing to a year of it. A plan that has been repriced upward twice in six months is likely to be repriced again — and a pack you are locked into is one you cannot leave when it happens.