Reducing our energy use has the dual benefit of lowering costs and greenhouse gas (GHG) emissions, and it is a central focus of both our environment, health, safety and social responsibility (EHS & SR) strategy and our Lean approach to managing the business. We generate and purchase energy primarily for power, processing, heating and cooling. In 2018 energy consumption from Hess-operated assets was approximately 31 million gigajoules, 7 percent lower than in 2017. This decrease was primarily related to reduced energy use resulting from asset sales in Equatorial Guinea and the Permian Basin and partially offset by increased energy use in our North Dakota, North Malay Basin and Gulf of Mexico operations related to a 30 percent production increase. Eighty-two percent of Hess’ energy use was directly generated from our operations, primarily at the Tioga Gas Plant and at our production facilities in North Dakota, North Malay Basin, Denmark and the Gulf of Mexico. The remaining 18 percent was indirect energy (energy used by utilities to provide net purchased electricity) purchased for the North Dakota production operations and the Tioga Gas Plant.
We seek opportunities to promote energy efficiency where feasible. As one example, we have been working to streamline the management of flights to our offshore assets in the Gulf of Mexico. Over the past five years our aviation contractors have moved more passengers while reducing the number of flights by 35 percent and reducing overall flying hours by 25 percent. This emphasis on improved logistics and flight management in the Gulf of Mexico operations has resulted in a reduction in fuel usage of approximately 103,000 gallons between 2017 and 2018, resulting in a reduction of approximately 1,000 tonnes of carbon dioxide equivalent (CO2e). This represents approximately 13 percent of Hess’ CO2e emissions from aviation fuels, excluding the Hess charter operated by United Airlines.
In 2018 our U.S. operations accounted for all of our purchased electricity – approximately 600,000 megawatt hours (MWh), or a 23 percent decrease from last year, primarily attributable to the sale of the Seminole Gas Plant (as part of the Permian Basin asset). Based on U.S. electricity generation profiles, we estimate that approximately 27 percent of this electricity was generated from renewable sources, primarily wind power. We also support renewable energy through the purchase of renewable energy certificates (RECs) equivalent to at least 10 percent of the net electricity used in our operations. In 2018 we purchased 70,000 Green-e Energy certified RECs for wind power, equivalent to 70,000 MWh or about 12 percent of the electricity purchased for our operated exploration and production assets. In total, including the RECs, approximately 39 percent of our indirect energy use came from renewable sources. In 2019 we are expanding our support of renewable energy by purchasing enough RECs to offset 100 percent of our purchased electricity.