Planning a move involves making numerous important decisions, decisions that if made poorly can really take a toll on your wallet. If your move involves renting a storage unit, as so many do, you have an added decision to make—one with potentially-higher financial stakes. Since storage units are paid for by the month and rented for months on end, the consequences of making a poor storage unit will compound over time. That’s why it’s imperative that you make the right decision from the very beginning.

The internet has made finding cheap storage units easier than ever. But while many of these sites make it easy to find a storage unit with a low monthly rent, they’re unable to add another important way to save money into their calculations: special deals offered up by the facilities themselves. When you’re comparing different storage facilities you’ll see that nearly all of them offer specials like ‘First Month’s rent $1’ or ‘1/2-off First Three Month’s Rent.’  Why not just offer a lower price? Because storage facilities all have different time-based goals to meet: some want to secure a customer for just a short-term stint of a month-or-two, while others want to tie the customer in for a longer period of time.

It just happens to be that you have different time-based goals in your move as well, and if you’re not factoring these special offers into your plans then you might be losing out. Let’s look at a hypothetical situation that proves that finding the right storage unit is not just about picking the facility with the lowest price. Let’s say you’re comparing two storage facilities, Facility A and Facility B. Facility A offers a storage unit for $50 a month with the special offer of your second month free of charge. Facility B offers a unit for $56 with the special deal of the first three months %50-off. So which is the better deal?

As you can see in the graph, it all depends on your own time frame. If you plan on using your storage unit for just two months then Facility A is the deal for you—those two months will cost just $50. But after two months, Facility B becomes the better deal. For three months at Facility B you’ll pay only $84 versus the $100 that Facility A will cost you. Facility B continues to be the superior deal until the sixth month (December in the graph), where it will cost just $196 to Facility A’s $200. At this point Facility A’s lower monthly price is beginning to catch up with the effects of the three-month half-off deal at Facility B. In the seventh month (January) Facility A once again becomes the better deal, at $250 to Facility B’s $252. The gap will continue to widen, as Facility B is now $6 a month more expensive than Facility A.

So what does this mean for you? If you’re only staying for two months, or seven months or longer, then Facility A offers you the best deal. If you’re planning on staying between three to six months, then Facility B is your choice.

Comparisons such as these highlight the importance of planning when it comes to finding the right storage unit. So plan ahead and figure out how long you’ll need to stay in your storage unit. Then compare time-based deals on offer at storage facilities in your new neighborhood. Finally, calculate how these offers match up with your own plans—sketching a graph like the one we made can make things easier. It could save you a lot of money.

Brian Shreckengast is a writer at SelfStorageDeals.com, the price-focused search engine for finding cheap self-storage units. Learn more about storing and how to do it for cheap at the Self Storage Blog.