investment tax credits have been deferred by the regulated utility subsidiaries and are being amortized to income over the average estimated service lives of the related assets . the company recognizes accrued interest and penalties related to tax positions as a component of income tax expense and accounts for sales tax collected from customers and remitted to taxing authorities on a net basis . see note 14 2014income taxes for additional information . allowance for funds used during construction afudc is a non-cash credit to income with a corresponding charge to utility plant that represents the cost of borrowed funds or a return on equity funds devoted to plant under construction . the regulated utility subsidiaries record afudc to the extent permitted by the pucs . the portion of afudc attributable to borrowed funds is shown as a reduction of interest , net on the consolidated statements of operations . any portion of afudc attributable to equity funds would be included in other , net on the consolidated statements of operations . afudc is provided in the following table for the years ended december 31: .
by how much did allowance for other funds used during construction increase from 2016 to 2018?
environmental costs the company 2019s water and wastewater operations and the operations of its market-based businesses are subject to u.s . federal , state , local and foreign requirements relating to environmental protection , and as such , the company periodically becomes subject to environmental claims in the normal course of business . environmental expenditures that relate to current operations or provide a future benefit are expensed or capitalized as appropriate . remediation costs that relate to an existing condition caused by past operations are accrued , on an undiscounted basis , when it is probable that these costs will be incurred and can be reasonably estimated . a conservation agreement entered into by a subsidiary of the company with the national oceanic and atmospheric administration in 2010 and amended in 2017 required the subsidiary to , among other provisions , implement certain measures to protect the steelhead trout and its habitat in the carmel river watershed in the state of california . the subsidiary agreed to pay $ 1 million annually commencing in 2010 with the final payment being made in 2021 . remediation costs accrued amounted to $ 4 million and $ 6 million as of december 31 , 2018 and 2017 , respectively . derivative financial instruments the company uses derivative financial instruments for purposes of hedging exposures to fluctuations in interest rates . these derivative contracts are entered into for periods consistent with the related underlying exposures and do not constitute positions independent of those exposures . the company does not enter into derivative contracts for speculative purposes and does not use leveraged instruments . all derivatives are recognized on the balance sheet at fair value . on the date the derivative contract is entered into , the company may designate the derivative as a hedge of the fair value of a recognized asset or liability ( fair-value hedge ) or a hedge of a forecasted transaction or of the variability of cash flows to be received or paid related to a recognized asset or liability ( cash-flow hedge ) . changes in the fair value of a fair-value hedge , along with the gain or loss on the underlying hedged item , are recorded in current-period earnings . the gains and losses on the effective portion of cash-flow hedges are recorded in other comprehensive income , until earnings are affected by the variability of cash flows . any ineffective portion of designated cash-flow hedges is recognized in current-period earnings. .