With front and rear 12-volt power points standard, a built-in 115-volt AC inverter is available to power a TV or appliances.

FORBES: Dodge Journey -- 19/26 mpg

The photovoltaic panels generate electricity when exposed to sunlight and are connected to the building's power supply via an inverter synchronised to the electricity main's frequency.

BBC: Solar power for City Works centre in Gloucester

Of course, leaving a smartphone's display on for multiple hours as you traverse Montana, Wyoming, Idaho, Oregon and California isn't wise without a power source to sustain that type of abuse, so it's worth mentioning that I traveled with an AC inverter in order to keep a constant power connection to the Lumia 900.

ENGADGET: Nokia Drive offline navigation review: taking the Lumia 900 for an off-the-grid spin

Despite all the talk of grid-based energy storage, the least expensive solution to the variability of wind and solar power is geographic dispersion, according to Leo Casey, Chief Technology Officer of Boston-based inverter company Satcon Technology, (NASD:SATC) speaking at the Building Energy 11 conference in Boston on March 9th.

FORBES: ABB Group Named Cleantech Company of the Year