cleanup of any PCB contamination that may have migrated to the Flushing River from the site, but such liability may be substantial.
Gowanus Canal In August 2009, CECONY received a notice of potential liability and request for information from the EPA about the operations of the company and its predecessors at sites adjacent or near the 1.8 mile Gowanus Canal in Brooklyn, New York.
The company understands that the EPA also has provided or will provide notices of potential liability and information requests to other parties.
In March 2010, the EPA added the Gowanus Canal to its National Priorities List of Superfund sites.
The canal’s adjacent waterfront is primarily commercial and industrial, currently consisting of concrete plants, warehouses, and parking lots, and the canal is near several residential neighborhoods.
In February 2011, the EPA released a report of its remedial investigation that confirmed there was significant contamination in the Gowanus Canal.
In December 2011, the EPA released a draft feasibility study that evaluated remedial alternatives.
The company expects that the cost of assessment and remediation of hazardous substances in and around the Gowanus Canal will be substantial.
CECONY is unable to predict its exposure to liability with respect to the Gowanus Canal site.
Other Superfund Sites CECONY is a potentially responsible party (PRP) with respect to other Superfund sites where there are other PRPs and where it is generally not responsible for managing the site investigation and remediation.
Work at these sites is in various stages, with the company participating in PRP groups at some of the sites.
Investigation, remediation and monitoring at some of these sites have been, and are expected to continue to be, conducted over extended periods of time.
The company does not believe that it is reasonably likely that monetary sanctions, such as penalties, will be imposed upon it by any governmental authority with respect to these sites.
The following table lists each of CECONY’s other Superfund sites for which the company anticipates it may have a liability.
The table also shows for each such site, its location, the year in which the company was designated or alleged to be a PRP or to otherwise have responsibilities with respect to the site (shown in the table under “Start”), the name of the court or agency in which proceedings with respect to the site are pending and CECONY’s estimated percentage of total liability for each site.
The company currently estimates that its potential liability for investigation, remediation, monitoring and environmental damages at each site is less than $0.2 million, with the exception of the Cortese Landfill site, for which the estimate is $1.1 million and the Curcio Scrap Metal site, for which the estimate is $0.3 million.
Superfund liability is joint and several.
The company’s estimate of its liability for each site was determined pursuant to consent decrees, settlement agreements or otherwise and in light of the financial condition of other PRPs.
The company’s actual liability could differ substantially from amounts estimated.
## Table 0 ##
O&R Superfund The sites at which O&R has been asserted to have liability under Superfund include its manufactured gas sites, its West Nyack site, the Newark Bay site, and other Superfund sites discussed below.
There may be additional sites as to which assertions will be made that O&R has liability.
For a further discussion of claims and possible claims against O&R under Superfund, see Note G to the financial statements in Item 8 (which information is incorporated herein by reference).
Manufactured Gas Sites O&R and its predecessors formerly owned and operated manufactured gas plants at seven sites (O&R MGP Sites) in Orange County and Rockland County, New York.
Three of these sites are now owned by parties other than O&R, and have been redeveloped by them for residential, commercial or industrial uses.
The NYSDEC is requiring O&R to develop and implement remediation programs for the O&R MGP Sites including any neighboring areas to which contamination may have migrated.
Through the end of 2011, O&R has completed remedial investigations at all seven O&R MGP Sites.
O&R has completed the remediation at one of its sites and a portion of another.
O&R has received NYSDEC’s decision regarding the remedial work to be done at three other sites and the remaining portion of a site where remediation has been completed.
Remedial design is ongoing for these sites and remedial construction is planned at one of the sites in 2012.
Feasibility studies will be completed for two sites in 2012.
West Nyack Site In 1991, 1994 and 1997, O&R entered into consent orders with the NYSDEC pursuant to which O&R agreed to conduct a remedial investigation and remediate certain property it owns in West Nyack, New York at which PCBs were discovered.
Petroleum contamination related to a leaking underground storage tank was found as well.
O&R has completed all
Electric O&R’s results of electric operations for the year ended December 31, 2018 compared with the year ended December 31, 2017 were as follows
## Table 1 ##
O&R’s electric sales and deliveries in 2018 compared with 2017 were
## Table 2 ##
(a) O&R’s New York electric delivery revenues are subject to a revenue decoupling mechanism, as a result of which, delivery revenues are generally not affected by changes in delivery volumes from levels assumed when rates were approved.
O&R’s electric sales in New Jersey are not subject to a decoupling mechanism, and as a result, changes in such volumes do impact revenues.
(b) “Residential/Religious” generally includes single-family dwellings, individual apartments in multi-family dwellings, religious organizations and certain other not-for-profit organizations.
(c)  Other electric operating revenues generally reflect changes in regulatory assets and liabilities in accordance with the company’s electric rate plan.
See Note B to the financial statements in Item 8.
(d) After adjusting for weather and other variations, electric delivery volumes in O&R’s service area increased 0.3 percent in 2018 compared with 2017.
Purchased power expenses increased $17 million in 2018 compared with 2017 due to higher purchased volumes ($15 million) and unit costs ($3 million).
Other operations and maintenance expenses increased $1 million in 2018 compared with 2017 due primarily to the reduction of a regulatory asset associated with certain site investigation and environmental remediation costs ($6 million), offset in part by lower surcharges for assessments and fees that are collected in revenues from customers ($3 million) and lower healthcare costs ($2 million).
Depreciation and amortization increased $5 million in 2018 compared with 2017 due primarily to higher electric utility plant balances.
Taxes, other than income taxes decreased $1 million in 2018 compared with 2017 due primarily to lower property taxes.
Gas O&R’s results of gas operations for the year ended December 31, 2018 compared with the year ended December 31, 2017 were as follows:
WESTROCK COMPANY NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued) 99 Consistent with prior years, we consider a portion of our earnings from certain foreign subsidiaries as subject to repatriation and we provide for taxes accordingly.
However, we consider the unremitted earnings and all other outside basis differences from all other foreign subsidiaries to be indefinitely reinvested.
Accordingly, we have not provided for any taxes that would be due.
As of September 30, 2019, we estimate our outside basis difference in foreign subsidiaries that are considered indefinitely reinvested to be approximately $1.6 billion.
The components of the outside basis difference are comprised of purchase accounting adjustments, undistributed earnings, and equity components.
Except for the portion of our earnings from certain foreign subsidiaries where we provided for taxes, we have not provided for any taxes that would be due upon the reversal of the outside basis differences.
However, in the event of a distribution in the form of dividends or dispositions of the subsidiaries, we may be subject to incremental U. S.  income taxes, subject to an adjustment for foreign tax credits, and withholding taxes or income taxes payable to the foreign jurisdictions.
As of September 30, 2019, the determination of the amount of unrecognized deferred tax liability related to any remaining undistributed foreign earnings not subject to the Transition Tax and additional outside basis differences is not practicable.
A reconciliation of the beginning and ending amount of gross unrecognized tax benefits is as follows (in millions)
## Table 3 ##
(1) Amounts in fiscal 2019 relate to the KapStone Acquisition.
Amounts in fiscal 2018 and 2017 relate to the MPS Acquisition.
(2) Additions for tax positions taken in current fiscal year includes primarily positions taken related to foreign subsidiaries.
(3) Amounts in fiscal 2019 relate to the settlements of state and foreign audit examinations.
Amounts in fiscal 2018 relate to the settlement of state audit examinations and federal and state amended returns filed related to affirmative adjustments for which there was a reserve.
Amounts in fiscal 2017 relate to the settlement of federal and state audit examinations with taxing authorities.
As of September 30, 2019 and 2018, the total amount of unrecognized tax benefits was approximately $224.3 million and $127.1 million, respectively, exclusive of interest and penalties.
Of these balances, as of September 30, 2019 and 2018, if we were to prevail on all unrecognized tax benefits recorded, approximately $207.5 million and $108.7 million, respectively, would benefit the effective tax rate.
We regularly evaluate, assess and adjust the related liabilities in light of changing facts and circumstances, which could cause the effective tax rate to fluctuate from period to period.
Resolution of the uncertain tax positions could have a material adverse effect on our cash flows or materially benefit our results of operations in future periods depending upon their ultimate resolution.
See “Note 18.
Commitments and Contingencies — Brazil Tax Liability” We recognize estimated interest and penalties related to unrecognized tax benefits in income tax expense in the consolidated statements of income.
As of September 30, 2019, we had liabilities of $80.0 million related to estimated interest and penalties for unrecognized tax benefits.
As of September 30, 2018, we had liabilities of $70.4 million, related to estimated interest and penalties for unrecognized tax benefits.
Our results of operations for the fiscal year ended September 30, 2019, 2018 and 2017 include expense of $9.7 million, $5.8 million and $7.4 million, respectively, net of indirect benefits, related to estimated interest and penalties with respect to the liability for unrecognized tax benefits.
As of September 30, 2019, it is reasonably possible that our unrecognized tax benefits will decrease by up to $8.7 million in the next twelve months due to expiration of various statues of limitations and settlement of issues.

<table><tr><td> Site</td><td> Location</td><td> Start</td><td> Court or Agency</td><td> % of Total Liability</td></tr><tr><td>Maxey Flats Nuclear</td><td>Morehead, KY</td><td>1986</td><td>EPA</td><td>0.8%</td></tr><tr><td>Curcio Scrap Metal</td><td>Saddle Brook, NJ</td><td>1987</td><td>EPA</td><td>100%</td></tr><tr><td>Metal Bank of America</td><td>Philadelphia, PA</td><td>1987</td><td>EPA</td><td>0.97%</td></tr><tr><td>Cortese Landfill</td><td>Narrowsburg, NY</td><td>1987</td><td>EPA</td><td>6.0%</td></tr><tr><td>Global Landfill</td><td>Old Bridge, NJ</td><td>1988</td><td>EPA</td><td>0.3%</td></tr><tr><td>Borne Chemical</td><td>Elizabeth, NJ</td><td>1997</td><td>NJDEP</td><td>0.7%</td></tr></table>
<table><tr><td></td><td colspan="3">For the Years Ended December 31,</td></tr><tr><td>(Millions of Dollars)</td><td>2018</td><td>2017</td><td>Variation</td></tr><tr><td>Operating revenues</td><td>$642</td><td>$642</td><td>$—</td></tr><tr><td>Purchased power</td><td>208</td><td>191</td><td>17</td></tr><tr><td>Other operations and maintenance</td><td>233</td><td>232</td><td>1</td></tr><tr><td>Depreciation and amortization</td><td>56</td><td>51</td><td>5</td></tr><tr><td>Taxes, other than income taxes</td><td>52</td><td>53</td><td>-1</td></tr><tr><td>Electric operating income</td><td>$93</td><td>$115</td><td>$-22</td></tr></table>
<table><tr><td></td><td colspan="4">Millions of kWh Delivered</td><td colspan="4">Revenues in Millions (a)</td></tr><tr><td></td><td colspan="2">For the Years Ended</td><td colspan="2"></td><td colspan="2">For the Years Ended</td><td colspan="2"></td></tr><tr><td>Description</td><td>December 31, 2018</td><td>December 31, 2017</td><td>Variation</td><td>Percent Variation</td><td>December 31, 2018</td><td>December 31, 2017</td><td>Variation</td><td>PercentVariation</td></tr><tr><td>Residential/Religious (b)</td><td>1,713</td><td>1,567</td><td>146</td><td>9.3%</td><td>$326</td><td>$311</td><td>$15</td><td>4.8%</td></tr><tr><td>Commercial/Industrial</td><td>799</td><td>763</td><td>36</td><td>4.7</td><td>115</td><td>113</td><td>2</td><td>1.8</td></tr><tr><td>Retail choice customers</td><td>2,974</td><td>2,976</td><td>-2</td><td>-0.1</td><td>201</td><td>201</td><td>—</td><td>—</td></tr><tr><td>Public authorities</td><td>131</td><td>105</td><td>26</td><td>24.8</td><td>12</td><td>9</td><td>3</td><td>33.3</td></tr><tr><td>Other operating revenues (c)</td><td>—</td><td>—</td><td>—</td><td>—</td><td>-12</td><td>8</td><td>-20</td><td>Large</td></tr><tr><td>Total</td><td>5,617</td><td>5,411</td><td>206</td><td>3.8%(d)</td><td>$642</td><td>$642</td><td>$0</td><td>—</td></tr></table>
<table><tr><td></td><td>2019</td><td>2018</td><td>2017</td></tr><tr><td>Balance at beginning of fiscal year</td><td>$127.1</td><td>$148.9</td><td>$166.8</td></tr><tr><td>Additions related to purchase accounting<sup>-1</sup></td><td>1.0</td><td>3.4</td><td>7.7</td></tr><tr><td>Additions for tax positions taken in current year<sup>-2</sup></td><td>103.8</td><td>3.1</td><td>5.0</td></tr><tr><td>Additions for tax positions taken in prior fiscal years</td><td>1.8</td><td>18.0</td><td>15.2</td></tr><tr><td>Reductions for tax positions taken in prior fiscal years</td><td>- 0.5</td><td>- 5.3</td><td>- 25.6</td></tr><tr><td>Reductions due to settlement<sup>-3</sup></td><td>- 4.0</td><td>- 29.4</td><td>- 14.1</td></tr><tr><td>(Reductions) additions for currency translation adjustments</td><td>-1.7</td><td>-9.6</td><td>2.0</td></tr><tr><td>Reductions as a result of a lapse of the applicable statute oflimitations</td><td>- 3.2</td><td>- 2.0</td><td>- 8.1</td></tr><tr><td>Balance at end of fiscal year</td><td>$224.3</td><td>$127.1</td><td>$148.9</td></tr></table>

Question: What is the difference between the greatest Revenues in Millions (a) in December 31, 2018 and December 31, 2017？ (in million)
Answer: 15