This simple labelling trick could make gadgets last longer -- and help save the planet

That's according to a new study from Germany's Environment Agency (UBA), which notes that shorter product lifespans means more waste, more pollution and higher consumption of energy and raw materials.

The study found no evidence of "planned obsolescence" -- the notion that manufacturers design their products to fail systematically after a certain period, to oblige customers to purchase a replacement.

But it did note a significant increase in early product failures, at least of larger appliances: The proportion replaced due to a defect within five years of purchase rose from 3.5 percent in 2004 to 8.3 percent in 2013.

One problem for consumers is that it's hard to know how long a product has been designed to last. The agency wants manufacturers to label products with their typical life expectancy -- as is often done for light bulbs -- to show their commitment to higher quality, longer-lasting devices.

At the same time, the agency acknowledged that measuring the lifetime of something like a phone or a washing machine would not be easy. It suggests operating hours as the basis for labeling, but that measure may be harder to understand than the years of use by which people tend to plan their budgets.

Units of measurement aside, labeling could encourage buyers to commit to using a device for a longer period. Too many people replace devices that are still in good working order, and consumers should use products for longer to reduce the pollution created during manufacturing and disposal, the agency said.

Manufacturers could also extend the lifespan of products in other ways, such as making them easier to repair.

That's the direction Dutch mobile phone company FairPhone is taking. The cases and components of its phones clip together, making them a little bulkier but easier to repair. Repair specialist iFixit gave FairPhone's second-generation model a perfect 10 for repairability, while Apple's iPhone 6 scored 7 out of 10, a little better than its predecessor. Paper-thin devices in which the subassemblies are glued together are inevitably harder to disassemble and reassemble.

Even if a device isn't irreparably broken, some people might persuade themselves that it's a good idea to replace it with a newer one on energy efficiency grounds. However, according to the agency it's better to hang on to older equipment, at least when it comes to larger appliances like washing machines.

"The energy demand and global warming potential during a life-time of five years is about 40 percent higher compared to a washing machine with a life-time of 20 years," the agency said.

But won't products keep improving, making the gain from a newer device more significant Well, no: These figures already take potential improvements in energy efficiency into account, according to the agency

Besides, as time goes on, the absolute gains in energy efficiency are getting ever smaller, whether we're talking about a mobile phone or a huge data center: Every 10 percent improvement is worth less than the last, a cycle of diminishing returns.

This is, perhaps, not what mobile phone manufacturers want to hear as they build up their booths in Barcelona for Mobile World Congress, the giant telecommunications trade show.

There they will launch new phones, many of them barely distinguishable from one another or from last years models.

However, this is what we want them to do, the environment agency notes: Consumers have come to expect new developments every year.

The agency's study, in German, looks at how to prevent obsolescence in household appliances large and small, consumer electronics, and information and communication technology products.