But the performance can vary widely, even among hybrids. Below, we spotlight the 10 most fuel-efficient cars based on Consumer Reports’ overall fuel-economy test results.

Most hot tub manufacturers and dealers ... How do solar-powered hot tubs compare in terms of energy efficiency? Solar power is a great source of energy, but the amount of available sunlight ...

OK, we admit, we're a long way from a carbon-free grid—but when we have one, what's the most efficient way to use that energy to fly planes? This question is explored by an interactive tool ...