Supplemental Balance Sheet Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013 Criteria Product	Dec. 31, 2012
Restricted Cash [Abstract]
Restricted cash	$ 129	$ 0
Receivables [Abstract]
Trade receivables	18,006	18,350
Allowance for doubtful accounts	446	488
Accounts receivable, net	17,560	17,862
Inventory [Abstract]
Raw materials	7,089	6,983
Work in process	2,527	2,429
Finished goods	1,641	3,516
Allowances for obsolescence	(1,827)	(1,849)
Inventories	9,430	11,079
Property and Equipment [Line Items]
Property and equipment, gross	24,830	24,671
Accumulated depreciation	(22,403)	(22,213)
Property and equipment, net	2,427	2,458
Accrued Expenses [Abstract]
Compensation and benefits	1,591	2,199
Warranty liability	699	694
Property, income, state, sales and franchise tax	656	320
Professional fees	558	502
Other	1,421	1,233
Accrued expenses	4,925	4,948
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	755
Warranty expense	182
Warranty charges incurred	(170)
Ending Balance	767
Warranty liability included in accrued expenses	699	694
Long-term warranty liability	68
Warranty accrual at end of period	767
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	10,400	10,298
Demonstration Units [Member]
Property and Equipment [Line Items]
Property and equipment, gross	1,810	1,828
Computers and Purchased Software [Member]
Property and Equipment [Line Items]
Property and equipment, gross	4,303	4,251
Furniture and Fixtures [Member]
Property and Equipment [Line Items]
Property and equipment, gross	457	444
Leasehold Improvements [Member]
Property and Equipment [Line Items]
Property and equipment, gross	7,753	7,662
Construction in Progress [Member]
Property and Equipment [Line Items]
Property and equipment, gross	$ 107	$ 188