entergy texas , inc . and subsidiaries management 2019s financial discussion and analysis gross operating revenues , fuel and purchased power expenses , and other regulatory charges gross operating revenues increased primarily due to the base rate increases and the volume/weather effect , as discussed above . fuel and purchased power expenses increased primarily due to an increase in demand coupled with an increase in deferred fuel expense as a result of lower fuel refunds in 2011 versus 2010 , partially offset by a decrease in the average market price of natural gas . other regulatory charges decreased primarily due to the distribution in the first quarter 2011 of $ 17.4 million to customers of the 2007 rough production cost equalization remedy receipts . see note 2 to the financial statements for further discussion of the rough production cost equalization proceedings . 2010 compared to 2009 net revenue consists of operating revenues net of : 1 ) fuel , fuel-related expenses , and gas purchased for resale , 2 ) purchased power expenses , and 3 ) other regulatory charges ( credits ) . following is an analysis of the change in net revenue comparing 2010 to 2009 . amount ( in millions ) .
from the growth in revenue , what percentage is attributed to the change in net wholesale revenue?
the net wholesale revenue variance is primarily due to increased sales to municipal and co-op customers due to the addition of new contracts . the volume/weather variance is primarily due to increased electricity usage primarily in the residential and commercial sectors , resulting from a 1.5% ( 1.5 % ) increase in customers , coupled with the effect of more favorable weather on residential sales . billed electricity usage increased a total of 777 gwh , or 5% ( 5 % ) . the rough production cost equalization variance is due to an additional $ 18.6 million allocation recorded in the second quarter of 2009 for 2007 rough production cost equalization receipts ordered by the puct to texas retail customers over what was originally allocated to entergy texas prior to the jurisdictional separation of entergy gulf states , inc . into entergy gulf states louisiana and entergy texas , effective december 2007 , as discussed in note 2 to the financial statements . the retail electric price variance is primarily due to rate actions , including an annual base rate increase of $ 59 million beginning august 2010 as a result of the settlement of the december 2009 rate case . see note 2 to the financial statements for further discussion of the rate case settlement . the securitization transition charge variance is due to the issuance of securitization bonds . in november 2009 , entergy texas restoration funding , llc , a company wholly-owned and consolidated by entergy texas , issued securitization bonds and with the proceeds purchased from entergy texas the transition property , which is the right to recover from customers through a transition charge amounts sufficient to service the securitization bonds . the securitization transition charge is offset with a corresponding increase in interest on long-term debt with no impact on net income . see note 5 to the financial statements for further discussion of the securitization bond issuance. .