It's almost irresistible to talk about your home as an investment. After all, home equity is the single largest component of the wealth of most households.

However, you shouldn't bet your retirement on it.

No single investment performs well enough, reliably enough, to finance your retirement. That includes your investment in the roof over your head.

The smart way to amass enough gold for your golden years is to spread your money around a thought-out mix of investments that includes a broad array of stocks, bonds and cash-equivalent investments such as certificates of deposit, Treasury investments and money-market funds. (Mutual funds make it easier to get a good mix.)

It's particularly important to put as much cash as allowed into tax-advantaged retirement accounts such as a 401(k) plan, especially if your boss will match your contribution.

Real estate can be a part of that mix if you put some money in the stocks of real estate investment trusts, or REITs, which invest in commercial and industrial real estate.

None of that, though, is as much fun as buying a new townhouse with a whirlpool tub.

So how should you think about the value of your home in the context of your overall finances? The respected Standard & Poor's/Case-Shiller Home Price Indices report refers to price changes as the return on a housing investment. For example: from July 2006 to July 2007, that "return" was a negative 7.2 percent for the far-flung Washington area.

But return is a term that is traditionally — and much more appropriately — applied to purchases of stocks and other easily traded investments. Return should not be confused with price. You can calculate your real return on any investment only after you account for the amount of cash you invested and the expenses incurred for interest payments and transaction fees, such as a real estate broker's commission.

The real financial return on the investment in your home could turn out to be the security of having a paid-off house in retirement or the accumulated home equity that you bequeath to your heirs. You can sell the house and use the equity to pay the entry fee to an assisted-living home, should that need arise.

Home equity certainly contributes to your wealth. But it won't necessarily fund a retirement full of golf, travel and spoiling the grandkids.

Karen Schaeffer, a certified financial planner in Rockville, Md., said she advises her clients not to even count their home equity when estimating whether their assets will be enough for retirement. "It doesn't help me retire unless I'm willing to sell it and live in something not as nice."

Schaeffer said that a lot of people tell her they plan to sell their local home when they retire and to relocate to a place where the cost of living is cheaper. But it doesn't always work out that way. "I've seen a lot of people relocate and spend every bit of their home equity," she said. "It's a lower-cost-of-living area, but they bought a nicer place."

She prefers to count home equity as a retirement asset only when the owners are at the point of selling and relocating. That equity is about to become cash. "Then I count it as part of their net worth," Schaeffer said.

She also makes a distinction between investment real estate and a vacation home that owners rent out part time. A condominium at the beach is best thought of as consumption, she said, not investment.

And she often advises clients to look for a more cost-effective way to get a couple of weeks at the beach each year instead of "tying up a lot of money" in a single asset and incurring carrying costs, such as property taxes, condo fees, insurance, repairs and maintenance.

Direct real estate investment — buying property and renting it out — can also be part of a financial strategy, Schaeffer said. "I'm a fan of their actually owning real estate that is easy to rent and easy to maintain."

There's a whole lot more involved with successfully investing in small rental properties than buying a place and later reselling it at a higher price. One must have the cash to repair and maintain the property, to pay taxes and insurance, to find good renters, to cover months when a property is vacant, and to deal with the occasional problem renter. Serious investors maximize their real estate profits by treating the rental as a business.

Equity in your home, and possibly in vacation homes or rental properties, can, over time, help you accumulate a good deal of wealth. But to generate cash for living comfortably during retirement, you also need to invest in something that doesn't come with a doorknob.