I may be a bear when it comes to Public Storage's (PSA -1.53%) valuation, but I'm all in favor of how it runs its balance sheet.

Public Storage is an outlier in real estate investment trusts. It issues very little debt, choosing to use preferred stock to finance new acquisitions and its ongoing operations. This is in stark contrast to other large REITs like Realty Income Corp. (O -0.42%) and National Retail Properties (NNN -1.74%), which issue relatively little preferred stock.

Why preferred stock rocks
Unlike a bond issue, preferred shares are permanent sources of capital. Preferred stock is essentially a loan where the principal balance is never repaid.

Public Storage used preferred shares to lock in its financing costs forever at rates that are near historical lows. If rates go up, Public Storage's financing costs will not -- its preferred shares pay a fixed-rate dividend. It doesn't have refinancing risk.

Other REITs that use debt may have to refinance it later at much higher rates than we see today when those debt securities mature.

Neither National Retail Properties nor Realty Income has adopted preferred stock as a large part of their capital structure. On the last earnings call, Realty Income CEO Tom Lewis answered one analyst's question about the company's funding sources. Lewis commented that he was comfortable with a range of 5%-15% preferred stock funding, later noting there is room for Realty Income to add leverage from debt and preferred stock.

Clearly, Realty Income favors debt rather than preferred stock issues. The same can be said for National Retail Properties, which finances roughly 13% of its capital structure with preferred stock. Public Storage operates with a whopping 39% of its funding from preferred stock.

Source: Company SEC filings.

Pay more now for lower rates forever?
Predicting interest rates isn't as easy as some might think. Managers have to concern themselves with profitability and a capital structure that maximizes shareholder value -- a financing structure that will bring the most people to pay the highest possible price for its shares.

I think most investors have come to terms with the fact that today's interest rates may be the lowest we see in years -- perhaps even our lifetime. For that reason, it may make sense for Realty Income and National Retail Properties to adopt Public Storage's financing strategy by using more sources of permanent capital to displace the effects of rising interest rates on their income statements.

Transitioning to permanent sources of capital is fairly easy. National Retail Properties and Realty Income simply allow their debt to mature, refinance part of it with short-term borrowings at a low rate, then sell perpetual preferred stock at a slightly higher rate than 20-year debt.

Sure, preferred stock may cost more right now, but the certainty may ease investors' minds about where rates are going next. Public Storage is in a very comfortable place knowing that it doesn't have to worry about rates going to 5% or even 10% in the next 10 years. Realty Income and National Retail Properties shareholders would probably appreciate the same kind of comfort.

It's not a question of preferred stock or debt; rather,it's a question of whether or not Realty Income and National Retail Properties should make a bigger effort to lock in low-cost funding forever. With rates so low, it may make sense to lock them in for the long haul as an insurance policy for equity investors.