Annual report pursuant to Section 13 and 15(d)

Stockholders' Equity (Deficit) (Details Textual)

v2.4.1.9
Stockholders' Equity (Deficit) (Details Textual) (USD $)
1 Months Ended 12 Months Ended 1 Months Ended 0 Months Ended
Apr. 30, 2014
Dec. 31, 2014
Dec. 31, 2013
Mar. 31, 2014
Dec. 15, 2014
Mar. 26, 2014
Mar. 07, 2014
Apr. 02, 2014
Class of Stock [Line Items]                
Common Stock, Shares Authorized   50,000,000us-gaap_CommonStockSharesAuthorized 40,000,000us-gaap_CommonStockSharesAuthorized     60,000,000us-gaap_CommonStockSharesAuthorized    
Preferred Stock, Shares Authorized   10,000,000us-gaap_PreferredStockSharesAuthorized 0us-gaap_PreferredStockSharesAuthorized     10,000,000us-gaap_PreferredStockSharesAuthorized    
Proceeds from Issuance Initial Public Offering   $ 24,872,170us-gaap_ProceedsFromIssuanceInitialPublicOffering $ 0us-gaap_ProceedsFromIssuanceInitialPublicOffering          
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount   3,261,360us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount 3,525,904us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount          
Sale of Stock, Price Per Share             $ 0.0001us-gaap_SaleOfStockPricePerShare  
Proceeds from Other Equity 700,000us-gaap_ProceedsFromOtherEquity 900,000us-gaap_ProceedsFromOtherEquity 0us-gaap_ProceedsFromOtherEquity          
Payments for Commissions 100,000us-gaap_PaymentsForCommissions 100,000us-gaap_PaymentsForCommissions            
Payments of Stock Issuance Costs   2,816,149us-gaap_PaymentsOfStockIssuanceCosts            
Common Stock [Member]                
Class of Stock [Line Items]                
Stock Issued During Period, Shares, New Issues   4,600,000us-gaap_StockIssuedDuringPeriodSharesNewIssues
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_CommonStockMember
           
Proceeds from Issuance or Sale of Equity 1,000,000us-gaap_ProceedsFromIssuanceOrSaleOfEquity
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_CommonStockMember
    1,000,000us-gaap_ProceedsFromIssuanceOrSaleOfEquity
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_CommonStockMember
       
Stock Issued During Period, Shares, Issued for Services 210,527us-gaap_StockIssuedDuringPeriodSharesIssuedForServices
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_CommonStockMember
210,527us-gaap_StockIssuedDuringPeriodSharesIssuedForServices
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_CommonStockMember
  210,527us-gaap_StockIssuedDuringPeriodSharesIssuedForServices
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_CommonStockMember
       
Proceeds from Other Equity 700,000us-gaap_ProceedsFromOtherEquity
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_CommonStockMember
    300,000us-gaap_ProceedsFromOtherEquity
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_CommonStockMember
       
IPO [Member]                
Class of Stock [Line Items]                
Stock Issued During Period, Shares, New Issues 4,600,000us-gaap_StockIssuedDuringPeriodSharesNewIssues
/ us-gaap_SubsidiarySaleOfStockAxis
= us-gaap_IPOMember
             
Shares Issued, Price Per Share               $ 6.00us-gaap_SharesIssuedPricePerShare
/ us-gaap_SubsidiarySaleOfStockAxis
= us-gaap_IPOMember
Proceeds from Issuance or Sale of Equity   25,214,596us-gaap_ProceedsFromIssuanceOrSaleOfEquity
/ us-gaap_SubsidiarySaleOfStockAxis
= us-gaap_IPOMember
           
Payments for Underwriting Expense   177,404us-gaap_PaymentsForUnderwritingExpense
/ us-gaap_SubsidiarySaleOfStockAxis
= us-gaap_IPOMember
           
Proceeds from Issuance Initial Public Offering   24,783,851us-gaap_ProceedsFromIssuanceInitialPublicOffering
/ us-gaap_SubsidiarySaleOfStockAxis
= us-gaap_IPOMember
    20,993,759us-gaap_ProceedsFromIssuanceInitialPublicOffering
/ us-gaap_SubsidiarySaleOfStockAxis
= us-gaap_IPOMember
     
Common Stock, Discount on Shares               2,208,000us-gaap_CommonStockDiscountOnShares
/ us-gaap_SubsidiarySaleOfStockAxis
= us-gaap_IPOMember
Payments of Stock Issuance Costs   430,745us-gaap_PaymentsOfStockIssuanceCosts
/ us-gaap_SubsidiarySaleOfStockAxis
= us-gaap_IPOMember
           
Over-Allotment Option [Member]                
Class of Stock [Line Items]                
Stock Issued During Period, Shares, New Issues   600,000us-gaap_StockIssuedDuringPeriodSharesNewIssues
/ us-gaap_SubsidiarySaleOfStockAxis
= us-gaap_OverAllotmentOptionMember
           
Secondary Offering [Member]                
Class of Stock [Line Items]                
Sale of Stock, Price Per Share         $ 7.00us-gaap_SaleOfStockPricePerShare
/ us-gaap_SubsidiarySaleOfStockAxis
= watt_SecondaryOfferingMember
     
Payments of Stock Issuance Costs         246,239us-gaap_PaymentsOfStockIssuanceCosts
/ us-gaap_SubsidiarySaleOfStockAxis
= watt_SecondaryOfferingMember
     
Stock Issued During Period, Value, Other         3,285,714us-gaap_StockIssuedDuringPeriodValueOther
/ us-gaap_SubsidiarySaleOfStockAxis
= watt_SecondaryOfferingMember
     
Secondary Offering [Member] | Underwriter [Member]                
Class of Stock [Line Items]                
Proceeds from Issuance or Sale of Equity         21,239,998us-gaap_ProceedsFromIssuanceOrSaleOfEquity
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= watt_UnderwriterMember
/ us-gaap_SubsidiarySaleOfStockAxis
= watt_SecondaryOfferingMember
     
Payments for Underwriting Expense         150,000us-gaap_PaymentsForUnderwritingExpense
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= watt_UnderwriterMember
/ us-gaap_SubsidiarySaleOfStockAxis
= watt_SecondaryOfferingMember
     
Common Stock, Discount on Shares         $ 1,610,000us-gaap_CommonStockDiscountOnShares
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= watt_UnderwriterMember
/ us-gaap_SubsidiarySaleOfStockAxis
= watt_SecondaryOfferingMember
     
Initial Public Offering Warrant [Member]                
Class of Stock [Line Items]                
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount   460,000us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
/ us-gaap_StatementClassOfStockAxis
= watt_InitialPublicOfferingWarrantMember
           
Investment Warrants, Exercise Price   $ 7.50invest_InvestmentWarrantsExercisePrice
/ us-gaap_StatementClassOfStockAxis
= watt_InitialPublicOfferingWarrantMember