There are important reasons to be cautious about when looking at new products. In some instances, these products will improve down the road; buy them now and you may get stuck with yesterday's technology. A pair of clear examples: hybrid cars and solar power systems.

Hybrid Cars: Can You Top This?

Toyota's (NYSE: TM) Prius virtually pioneered the hybrid car revolution. These cars have proven to be extremely thrifty and quite reliable. That has inspired other automakers to belatedly make a big push into the hybrid car market. In the last few months, Ford (NYSE: F) and Honda (NYSE: HMC) have launched all-new, mid-sized hybrid sedans that may represent the cream of the crop.

Ford's new Fusion, for example, gets 47 miles to the gallon, both in the city and on the highway. That's remarkable for a roomy sedan that comfortably seats five people. Honda's just-released 2013 Accord boasts strong mileage figures as well, with a hybrid drive-train that can be optimized by the customer according to driving conditions.

Yet here's what Honda, Ford, Toyota and others won't say publicly. Engineers at these firms are making so much progress that the 2014 and 2015 hybrids are expected to break new records in terms of miles per gallon.

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That's the sad lesson learned by people who bought Nissan's all-electric Leaf. The 2012 model was expensive and slow, and the battery packs have had some durability issues. The company realized it needed to make a series of improvements, and they've made solid progress with the 2013 model. They anticipate even more advances in the 2014 model. For the folks who bought the 2012 models, they'll find out in a few years that those cars aren't worth a lot on the resale market, simply because subsequent models offered much better technology.

Solar: Not There Yet

For many homeowners, an investment in solar power makes ample sense. After all, prices have come down steadily in recent years, in large part due to a decision by manufacturers to produce too many solar panels.

The glut of panels on the market is unlikely to abate: The industry's factories keep running at full bore. Of equal concern to today's buyers is the changing nature of solar technology. Billions of dollars have been spent in recent years on solar panel technology development, and that's translating into sunlight-to-power conversion ratios that improve every year. That trend will likely continue.

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Unlike cars, which last a decade or so, solar power installations are expected to last 20, 30 or 40 years -- that means you should make sure you own technology that won't go out of date in a decade.

That's not to say you should wait a decade to look at solar power. Instead, the curve of technology means solar power systems may be even more efficient in a few years. Said another way, we know the technology won't worsen a few years from now, nor are solar panels likely to become more expensive. The risk of waiting a few years more is zero.

The Investing Answer: We live in a time of rapid technological change, especially in the areas of transportation and power generation. Before plunking down 10s of thousands of dollars on hot new technology, research the imminent changes that will soon be incorporated into these models. For example, though Ford's 47 MPG claim for the new Fusion might seem impressive, auto analysts think we may be looking at cars getting 60 MPG in a few years.