Segment Information and Concentration of Risk	6 Months Ended
Jun. 30, 2018
Risks and Uncertainties [Abstract]
Segment Information and Concentration of Risk	Segment Information and Concentration of Risk Segments and the Chief Operating Decision Maker (CODM) The Company’s chief operating decision makers (CODMs), the Chief Executive Officer and the Chief Financial Officer, review financial information presented on a consolidated basis for purposes of allocating resources and evaluating financial performance. The CODMs allocate resources and make operational decisions based on direct involvement with the Company’s operations and product development efforts. The Company is managed under a functionally-based organizational structure with the head of each function reporting to the Chief Executive Officer. The CODMs assess performance, including incentive compensation, based upon consolidated operations performance and financial results on a consolidated basis. As such, the Company has a single reporting segment and operating unit structure. Concentration of Geographic Risk Substantially all of the Company’s revenue and long-lived assets are attributable to operations in the United States for all periods presented. Concentrations of Credit Risk Financial instruments that potentially subject the Company to a concentration of credit risk consist primarily of cash and cash equivalents, short-term investments, accounts receivables, customer financing lease receivables and counterparties to derivative instruments. The Company only invests cash and cash equivalents in institutions which maintain the highest ratings of creditworthiness. Short-term investments consist of U.S. Treasury Bills. The Company conducts periodic evaluations of the creditworthiness of its customers and the collectability of its accounts receivable and financing leases receivable and provides for potential credit losses as necessary in the consolidated financial statements. The Company limits its credit risk on derivative instruments by dealing only with counterparties that are considered to be of high credit quality. To date, the Company has neither provided an allowance for uncollectible accounts nor experienced any credit loss. Concentrations of Customer Risk The Company's Energy Servers are sold at a significant purchase price with few numerical sales in any given quarter. Consequently in any particular period, a substantial proportion of total revenue is concentrated in a relatively small number of customers. In subsequent periods, the same is true for a different set of customers. Therefore, although revenue is highly concentrated in a few customers in a single quarterly period, such is not the case when examining revenue over longer terms. In the three months ended June 30, 2018, total revenue from Macerich and The Southern Company represented 19% and 16% of the Company’s total revenue, respectively. In the six months ended June 30, 2018, total revenue from The Southern Company and Korea Energy represented 53% and 17% of the Company's total revenue, respectively. In the three months ended June 30, 2017, total revenue from Macerich and The Southern Company, represented 19% and 16% of the Company’s total revenue, respectively. In the six months ended June 30, 2017, total revenue from The Southern Company and Korea Energy represented 53% and 17% of total revenue, respectively. Concentrations of Supply Risk The Company’s products are manufactured using a rare earth mineral. The suppliers for this raw material are primarily located in Asia. A significant disruption in the operations of one or more of these suppliers could impact the production of the Company’s products which could have a material adverse effect on its business, financial condition and results of operations. Cybersecurity Risk All of the Company's installed Energy Servers are connected to and controlled and monitored by the Company's centralized remote monitoring service. Additionally, the Company relies on internal computer networks for many of the systems used to operate the business generally. The Company may be vulnerable to breaches, unauthorized access, misuse, computer viruses or other malicious code and cyber-attacks. The Company takes protective measures and endeavors to modify these internal systems as circumstances warrant to prevent unauthorized intrusions or disruptions.

Segment Information and Concentration of Risk

Segments and the Chief Operating Decision Maker (CODM)

The Company’s chief operating decision makers (CODMs), the Chief Executive Officer and the Chief Financial Officer, review financial information presented on a consolidated basis for purposes of allocating resources and evaluating financial performance. The CODMs allocate resources and make operational decisions based on direct involvement with the Company’s operations and product development efforts. The Company is managed under a functionally-based organizational structure with the head of each function reporting to the Chief Executive Officer. The CODMs assess performance, including incentive compensation, based upon consolidated operations performance and financial results on a consolidated basis. As such, the Company has a single reporting segment and operating unit structure.

Concentration of Geographic Risk

Substantially all of the Company’s revenue and long-lived assets are attributable to operations in the United States for all periods presented.

Concentrations of Credit Risk

Financial instruments that potentially subject the Company to a concentration of credit risk consist primarily of cash and cash equivalents, short-term investments, accounts receivables, customer financing lease receivables and counterparties to derivative instruments.

The Company only invests cash and cash equivalents in institutions which maintain the highest ratings of creditworthiness. Short-term investments consist of U.S. Treasury Bills. The Company conducts periodic evaluations of the creditworthiness of its customers and the collectability of its accounts receivable and financing leases receivable and provides for potential credit losses as necessary in the consolidated financial statements. The Company limits its credit risk on derivative instruments by dealing only with counterparties that are considered to be of high credit quality.

To date, the Company has neither provided an allowance for uncollectible accounts nor experienced any credit loss.

Concentrations of Customer Risk

The Company's Energy Servers are sold at a significant purchase price with few numerical sales in any given quarter. Consequently in any particular period, a substantial proportion of total revenue is concentrated in a relatively small number of customers. In subsequent periods, the same is true for a different set of customers. Therefore, although revenue is highly concentrated in a few customers in a single quarterly period, such is not the case when examining revenue over longer terms.

In the three months ended June 30, 2018, total revenue from Macerich and The Southern Company represented 19% and 16% of the Company’s total revenue, respectively. In the six months ended June 30, 2018, total revenue from The Southern Company and Korea Energy represented 53% and 17% of the Company's total revenue, respectively. In the three months ended June 30, 2017, total revenue from Macerich and The Southern Company, represented 19% and 16% of the Company’s total revenue, respectively. In the six months ended June 30, 2017, total revenue from The Southern Company and Korea Energy represented 53% and 17% of total revenue, respectively.

Concentrations of Supply Risk

The Company’s products are manufactured using a rare earth mineral. The suppliers for this raw material are primarily located in Asia. A significant disruption in the operations of one or more of these suppliers could impact the production of the Company’s products which could have a material adverse effect on its business, financial condition and results of operations.

Cybersecurity Risk

All of the Company's installed Energy Servers are connected to and controlled and monitored by the Company's centralized remote monitoring service. Additionally, the Company relies on internal computer networks for many of the systems used to operate the business generally. The Company may be vulnerable to breaches, unauthorized access, misuse, computer viruses or other malicious code and cyber-attacks. The Company takes protective measures and endeavors to modify these internal systems as circumstances warrant to prevent unauthorized intrusions or disruptions.