Property and Equipment
 12 Months Ended
Dec. 31, 2015
Property, Plant and Equipment [Abstract]  
Property and Equipment
PROPERTY AND EQUIPMENT
 
Property and equipment are stated at cost and depreciated using the straight-line method over the estimated useful lives of the related assets and consist of the following (in thousands):
  
 
At December 31,
 
2015
 
2014
 
 
 
 
Equipment (useful life 3 - 15 years)
$
2,864

 
$
1,289

Tooling (useful life 2 - 5 years)
851

 
851

Vehicles (useful life 5 years)
39

 
—

Furniture and fixtures (useful life 5 years)
104

 
85

Computer software (useful life 3 years)
581

 
378

Leasehold improvements (the shorter of useful life or lease life)
509

 
509

Construction in progress
310

 
18

Property and equipment at cost
5,258

 
3,130

Less: accumulated depreciation
(2,829
)
 
(2,674
)
Property and equipment, net
$
2,429

 
$
456


 
Depreciation expense was $266 thousand, $184 thousand, and $615 thousand for the years ended December 31, 2015, 2014 and 2013, respectively.