The last thing cruise lines want is too many empty cruise ship cabins on any given sailing. Unsold cruise cabins mean fewer passengers to spend money on drinks, excursions, in the spa and at alternative restaurants.
With a goal of more than 100 percent occupancy on every sailing (meaning the number of passengers onboard is equal to or higher than the double-occupancy capacity of the ship), cruise lines have a variety of tactics for filling empty cabins -- most of which can result in deep savings for cruisers in the know.
But getting a deal on a cruise sailing that's not selling well requires some effort -- and usually a lot of flexibility. Because cruise lines will not start discounting until they have to (usually after final payment is due for that sailing), you'll need to be ready to travel within one to two months (or less) to take advantage of the low prices triggered by unsold cruise cabins.
To take advantage of the opportunity empty cruise cabins present, you must understand how cruise lines go about filling them.
Cruise lines fill unsold cabins in a two-stage process, in order to protect as much revenue as possible.
It's much more palatable for cruise lines to publicly sell their lower-priced cabins (insides and ocean views) at discounted rates than to advertise deep reductions on balcony-level rooms or suites. That's because it's better to lose $300 by discounting an $800 inside cabin to $500, than to lose $500 by cutting the cost of a $2,200 suite to $1,700, especially considering all the perks that a suite passenger gets.
In order to fill the higher categories first, cruise lines will typically try to upsell already-booked passengers. Keep in mind, most upper categories do sell out with little extra effort from the cruise lines.
So cruisers who have already booked and paid for a balcony might get a call from a cruise line sales representative or their travel agent, offering them a suite for a couple hundred dollars more (for a total suite cost less than its advertised price). This fills up the suites, and empties the balcony cabins which will then be offered to those who booked ocean-view cabins for a small upgrade fee.
A few lines have introduced invitation-only bidding for upgrades, directed at loyal past passengers or cruisers in specific cabin categories. Instead of the cruise line offering an upgrade at a specific price, cruisers bid how much they think it's worth to pay for a higher-category cabin. The cruise line can then make a final decision based on cabin-filling needs and the best offers from passengers.
The remaining unsold cruise cabins (mostly lower category options, but not always) will typically be offered to select groups of cruisers through several methods.
Cruise lines will offer many of the remaining cabins at exclusive sale prices to partner travel agencies with an ability to move lots of capacity (think huge Internet agencies or land-based big-box travel retailers).
The lines will also try to sell empty cabins via resident discounts to cruisers from the state from which the cruise ship sails. Cruise lines might also advertise a flash sale to subscribers of its e-letter or to its Twitter followers.
Cruise lines are not going to flag specific sailings as having empty cabins, making it easy for a potential booker to find a deal. If you want to save, you'll need to make some effort.
The easiest way to find out about sales is to sign up for the cruise line's e-letter or follow the line on Twitter and Facebook; do this for every cruise line you're interested in. The lines will advertise flash sales through these outlets.
Also, get on the mailing list of large travel agencies (Cruise.com, Vacations to Go, CruiseOne, Cruise Planners, etc). If they're asked to fill cabins, they'll advertise the exclusive discounts through their e-letters.
If you have a specific sailing in mind, you'll want to be doing mock bookings for that sailing starting the week after final payment is due. During the booking process you'll be able to see how many cabins in any category are left.
If you're already booked on that cruise and see that there are open higher-category rooms than what you've got booked, contact the line or your travel agent to see if there are any upgrade offers open.
It's more difficult if you're not already booked. If you see lots of empty cruise cabins, you can try contacting the line to see if a sales rep or a travel agency will offer you a good deal. Chances are high, however, that if no sale is advertised on the website, you won't be offered a discount.
If this is the case, keep checking in. If cabins don't start filling up as the sail date gets closer, the chances of a sale popping up increase.
Be aware: If your cabin search results in only a handful of empty rooms, chances are there will be no deals offered. This is because a cruise ship can reach its double-occupancy number without filling every cabin (due to filling third, fourth and fifth berths, not to mention cribs and rollaway cots). Cruise lines breathe easier about financials when that passenger count is reached, so they're not always bothered to offer you a discount on their very last unsold cabin.