Supplemental Balance Sheet Information (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Dec. 31, 2011
Restricted Cash [Abstract]
Restricted cash	$ 386	$ 389
Receivables [Abstract]
Trade receivables	18,328	11,500
Allowance for doubtful accounts	(662)	(337)
Accounts receivable, net	17,666	11,163
Inventory [Abstract]
Raw materials	6,897	6,493
Work in process	2,769	3,085
Finished goods	942	1,680
Allowances for obsolescence	(1,246)	(1,819)
Inventories	9,362	9,439
Property and Equipment [Line Items]
Property and Equipment, Gross	25,061	24,255
Accumulated depreciation	(22,165)	(21,394)
Property and equipment, net	2,896	2,861
Accrued Expenses [Abstract]
Compensation and benefits	1,844	3,037
Warranty liability	614	583
Property, income, state, sales and franchise tax	336	529
Professional fees	466	463
Other	589	739
Accrued expenses	3,849	5,351
Warranty Liability [Abstract]
Standard power quality products warranty period from date of commissioning	12 months
Standard power quality products warranty period from date of shipment	18 months
Standard products warranty period for primary OEM customer	12 months
Extended products warranty period from date of shipment to primary OEM customer, Maximum	36 months
Changes in warranty liability [Roll Forward]
Beginning Balance	613
Warranty expense	1,060
Warranty charges incurred	(1,009)
Ending Balance	664
Warranty liability included in accrued expenses	614	583
Long-term warranty liability	50
Ending Balance	664
Revenue Recognition [Abstract]
Number of criteria to be met for revenue recognition	4
Minimum number of CleanSource UPS or PowerHouse products included in significant MEAs	1
Minimum number of second tier products included in significant MEAs	1
Commissioning and installation period	6 months
EMAs, consumables, repair, maintenance and consulting services general deliverable period, minimum	1 year
EMAs, consumables, repair, maintenance and consulting services general deliverable period, maximum	5 years
Equipment [Member]
Property and Equipment [Line Items]
Property and Equipment, Gross	10,060	9,980
Demonstration Units [Member]
Property and Equipment [Line Items]
Property and Equipment, Gross	2,149	1,345
Computers and Purchased Software [Member]
Property and Equipment [Line Items]
Property and Equipment, Gross	4,177	4,029
Furniture and Fixtures [Member]
Property and Equipment [Line Items]
Property and Equipment, Gross	375	369
Leasehold Improvements [Member]
Property and Equipment [Line Items]
Property and Equipment, Gross	7,647	7,425
Construction in Progress [Member]
Property and Equipment [Line Items]
Property and Equipment, Gross	$ 653	$ 1,107