Since 2002, a trade magazine for contractors and builders called “Remodeling” has been tracking how much it costs to do common home improvement projects — and then calculating how much of that cost is recovered when the home sells.

Each year, we highlight the projects with the highest return on investment from the magazine’s Cost vs Value Report.

But this year, we decided to focus not just on the new data, but how projects have performed since 2002.

So, what’d we find?

Well, you may want to reconsider turning that spare room into a full-fledged office. A home office remodel had the worst overall ROI of 53%; the project’s been declining since it was added to the study in 2005 with an ROI of 72.8%.

The biggest jump we’ve seen? Backup generators, which had some of the lowest ROI rates over the years — as low as 47.5% in 2011 — leapt to 52.7% in 2012 and then took an almost 15 point jump to 67.5% in 2013! We can be pretty sure Hurricane Sandy and extreme weather in recent years are a big part of the reason.

But the real gems are those projects that don’t have such highs and lows — the ones with consistent ROI.

We’re not saying these steady and reliable projects are the ‘right’ ones for you. If a home office will improve your quality of life and help you enjoy your home more, then it makes sense. We just think knowing what’s going to happen with your remodeling dollars makes sense, too.

So, which ones are the long-term winners? The projects that share these four characteristics:

• Low-maintenance
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• Good — but not necessarily the highest — quality

• Energy-efficient

• Not too costly

Read the rest of the article here.