The loop or the one big trip

We live in a small town with three grocery stores in it and one very large one about forty minutes away. Every week, usually on a Saturday morning with coffee, the same conversation happens in our kitchen. Do we drive out to the big store and get everything in one go, or do we do the round of the three near ones? For years we answered by habit, and the habit changed depending on who was tired. Then we started writing the numbers down, and the answer turned out to be less obvious than either of us thought.

The two things a trip costs

A shopping trip costs time and it costs money, and the two are surprisingly easy to confuse. The time is the driving, plus something for every stop along the way. Parking, walking in, finding the thing you came for, standing in the line at the checkout. For a store you know well, ten minutes a stop is a fair guess, and it is ten minutes whether you are buying two things or twenty. The money is what the same list would come to at each store, by the prices you have actually paid there.

What makes the decision interesting is that the two costs rarely point the same way. The big store out of town tends to be cheaper on the staples and dearer in time. The corner store is close and quick and charges more for milk. A round of three near stores can cost less in fuel and more in an afternoon than the long drive would have.

What the big trip hides

The store that has everything is tempting because it removes the decision. Every item on the list is in there somewhere, and you will come home with all of it. What it hides is the drive. Forty minutes each way is more than an hour of a Saturday before a single thing is in the cart, and the hour comes out of the same afternoon the rest of the shopping does. It also hides the assumption that the big store is cheaper on everything. In our own price book it is not. Bread and milk and eggs are usually a little cheaper at the small store down the road, and the big store wins on rice and coffee and cleaning things by a wider margin than we expected.

What the loop hides

The round of near stores hides its cost in the stops. Each one costs those ten minutes of parking and walking and queueing, on top of the drive between them. Three stops for eleven items is a great deal of parking for eleven items. The loop also needs discipline. The second store has the thing you forgot at the first one, and it has three other things you did not plan to buy. Our loop trips cost more in unplanned purchases than the big trips do, and it took a few months of receipts to see that.

A rule of thumb that mostly works

After a while we settled on two limits, and between them they decide most weeks. Once the list passes about fifteen items, the one big trip wins, because the saving on that many staples is worth the drive. Once the round would take three stops or more, the one big trip wins again, because three lots of parking is an afternoon. Below both limits it is a closer call, and the honest way to make it is to add the minutes up and set them against what your own prices say you would save.

ManyStops does that arithmetic for us now. The Plan screen lays out the one big trip and the round side by side, each with its stops, its driving time and what the list would come to by the prices we have recorded, and it marks the one it would choose with the reasons behind it. The two limits are ours to change, and yours to change on your own account, because a household with a car and a household with a bus pass will not agree on where they sit.

The third answer

The thing nobody told us, and the thing that saved us the most, is that some weeks the right answer is neither. If nothing on the list has actually run out, and everything that is running low will last until the weekend, the trip can wait. Waiting is the cheapest option there is, and it is the one no store will ever suggest, because every store is built to bring you in.

A list that knows how often you buy each thing can tell you when a trip can wait. ManyStops says it above the options, with the day it thinks you can hold out until and the item that will run out first. Then the decision is yours, with the numbers in front of you. Some weeks we look at that line, close the app, and go back to our coffee.

Read next: Is the warehouse club worth it? Work it out from your receipts