Derivative Instruments (Tables)

6 Months Ended

Jun. 30, 2018

Derivative Instruments

Schedule of notional volume of natural gas derivatives that is expected to settle or mature each year

Year	Natural Gas Swaps (MMBTUs) (in millions)
2018	15.4
2019	21.6
2020	18.4
2021	16.8
2022	10.7
2023	0.2
Total	83.1

Schedule of fair value of derivative instruments and effect on consolidated balance sheets

The table below reflects the fair value of derivative instruments and their effect on our consolidated balance sheets at June 30, 2018 and December 31, 2017.

	Balance Sheet Location		Fair Value
			2018		2017
			(dollars in thousands)
Assets:
Natural gas swaps	Other current assets	$	1,228	$	412
Liabilities:
Natural gas swaps	Other current liabilities	$	747	$	1,575
Natural gas swaps	Other deferred credits	$	11,863	$	5,165

Schedule of the realized gains and (losses) on derivative instruments recognized in margin

	Statement of Revenues and Expenses Location		Three months ended June 30,						Six months ended June 30,
			2018			2017			2018			2017
			(dollars in thousands)
Natural Gas Swaps	Fuel	$	359		$	1,897		$	1,751		$	2,736
Natural Gas Swaps	Fuel		(111	)		(73	)		(859	)		(817	)
Total		$	248		$	1,824		$	892		$	1,919

Schedule of unrealized losses on derivative instruments deferred on the balance sheet

The following table presents the unrealized losses on derivative instruments deferred on the balance sheet at June 30, 2018 and December 31, 2017.

	Balance Sheet Location		2018			2017
			(dollars in thousands)
Natural gas swaps	Regulatory asset	$	(11,382	)	$	(6,328	)
Total		$	(11,382	)	$	(6,328	)