Vehicle Lease vs Buy Decision (an Excel model)

I recently helped my fiancée decide between leasing and purchasing a new car. When I could not find a model helping evaluate the relative economic attractiveness of a lease, I built one. You can download it here. Below, is an explanation of the logic driving the model. If you have any questions or feedback, please let me know.


The model is pretty straightforward, and allows you to compare one loan to one lease at a time. The model will tell you if the lease or the loan is economically better, and by how much.


Evaluating the economic attractiveness of a car loan versus lease essentially requires calculating the “equity”–whether realizable (in the case of loan) or not (in the case of lease)–you as the leasor would have in the vehicle when the would-be lease ends. The vehicle’s value at some future point in time doesn’t depend on your lease / buy decision. Thus, the only question is what the vehicle’s value will be (vehicle purchase price less depreciation) and how much you will have paid through that forward moment in time (sum of your payments).

Determining the economic attractiveness of a car loan is easier because it is as simple as calculating the equity you would have in the vehicle. Evaluating economic attractiveness of a lease was slightly trickier to figure out because you don’t actually own the car when the lease terminates.

The way I thought about how to evaluate a lease is to look at the lease from the leasor’s perspective. If the lease is good for the leasor, it is bad for you. Conversely, if it is good for you, it is bad for the leasor. So we want to look for the scenario wherein it is bad for the leasor. A lease is a bad deal for the leasor if the leasee doesn’t pay for all of the vehicle’s depreciation upon return of the vehicle. In such a case the vehicle will have lost $X dollars of value (due to depreciation) and the leasor will have received less than $X dollars of payments from the leasee. Hence, a lease is good deal for the leasee if the sum of your payments is less than the vehicle’s lost value. In such a case, the leasor is essentially paying for some of the vehicle’s depreciation, instead of you.

If this is still not clear, consider the following. The ideal lease for a leasor is one in which the leasee’s total payments exceed the total depreciation of the vehicle, such that the leasor can then sell the vehicle at market value for a profit. When selling the vehicle, we can safely assume that leasor will not be able to sell it for more than it’s expected market value (purchase price less depreciation), which acts as the max expected sales price. Now, since the leasee paid the leasor X dollars of payments, and the vehicle depreciated by W from Z and is now worth Y, to sell a vehicle at a profit, the leasor must sell the vehicle for at least Y-(X-W).  As you can see from this equation, the more money the leasee pays (ie. the larger X gets), the lower the minimum profitable sales price becomes, thus increasing the likely profit that the leasor will make upon selling of the vehicle.


fundamentally flawed bank underwriting

A lot of friends, who weren’t bankers, have asked me to explain the whole financial crisis thing to them.  So far, I do not know of anyone who has made the explanatory point I share below; but I am sure someone has.  Regardless of whether someone has published this explanation, one thing about the financial crisis really has me confounded.

I just find it hard to believe that professional bankers with decades of banking experience didn’t realize they were helping “blow up the bubble” and push home prices higher with the generous liquidity they were providing to home buyers.  Lenders providing financing to consumers enabled consumers to then make  higher bids on real estate properties, and these generous bids then become the sales prices at which the property was sold, which is then fed back into the bankers financing decisions in the form of “comp” values, which bankers use to determine how much they can lend against the property, which is the collateral securing the loan.

So what’s the solution?   Shouldn’t real estate lending practices simply be a simple function of the borrower’s ability to pay the proposed mortgage; not on a forecasted sales price the property could be expected to sell for at some point in the future?   That is, bankers can simply look at the borrowers income and expenses and determine how much the borrower can afford in terms of monthly mortgage payments; and then back into how much the borrower can afford to borrow given the market interest rates and time duration of the loan.

Had lending practices been based on these exogenous means for affording real estate properties, I think it would have been very easy to see the “bubble” forming, because a “safe demand” (i.e. people’s ability to afford mortgage payments) for real estate properties could have been measured by measuring people’s income and wealth, minus the value of the real estate properties owned by people.