Refundable or non-refundable?
It depends on the premium, and on whether anyone watches the price.

When a refundable booking and a rebook come out ahead

Say the cheapest non-refundable rate is $200 a night and free cancellation costs 9% more, $218. You book the refundable one. Later the price falls and you rebook. You only end up below the $200 you passed up if the rate you rebook at is under $200: a fall of more than $18, or about 8.3% of $218.

The rule: if free cancellation costs p more, the rate has to fall by more than p ÷ (1 + p) before the rebook beats the non-refundable price. In our data:

So the cheaper the flexibility, the easier it is to come out ahead, and the price of flexibility varies a lot: at 1,535 of the 3,975 hotels with both kinds of listing (39%), the difference was 5% or less. Nobody can tell you in advance whether a price will fall. What you can control is how much you pay for the option, and whether anyone is watching when it does.

When non-refundable is the better deal

When your dates are fixed, the premium is large, and you won't look at the price again. A refundable rate only turns into a lower price if you notice the drop before your free cancellation ends. If nobody checks, you paid for an option you never used.

Already on a non-refundable rate and the price fell? Rebooking won't get your money back, but there are a few things to try: what still works on a non-refundable booking.

"Free cancellation" in our figures is the label Google Hotels shows for a site's listed rate; "non-refundable" means a listing without that label. Most of those are non-refundable, but some may allow a partial refund or show their terms only on the site. Read the terms on the site itself before you book.

Make the refundable rate earn its premium

The option is only worth something if someone checks the price before your free cancellation ends. We can do that part.

• You tell us what you paid per night, with taxes and fees, and the last day you can cancel for free.
• We check the rates listed for your hotel and dates once a day.
• We email you once if a listed rate is at least 5% lower than what you paid (and at least $5 a night lower, or about that in your currency) on two daily checks in a row. The email names the site and the price.
• You check the room before you rebook. A lower rate can be for another room, bed type or meal plan. You book and cancel yourself; we never do either.
• We stop at your free-cancellation date. We need two checks in a row, so a rate that first drops on your deadline day itself comes too late for an alert.

Free, no account. We never ask for your booking number, your name or your payment details.