MWP Markwest Hydrocarbon,

MarkWest Energy Partners, L.P. (NYSE:MWE) and MarkWest Hydrocarbon, Inc. (AMEX:MWP) today announced the preliminary results of the merger consideration elections for the previously announced Agreement and Plan of Redemption and Merger (the �Redemption and Merger Agreement�) between the two companies. Approximately 12,025,399 shares of MarkWest Hydrocarbon common stock were outstanding on February 20, 2008, and entitled to participate in the election of merger consideration. Of this amount, preliminary tabulations indicate 1,767,805 shares elected to receive cash consideration, 2,814,320 shares elected to receive common units of MarkWest Energy Partners, 6,285,940 shares elected to receive the stated consideration of 1.285 common units and $20.00 cash per share, and 622,271 made no election. In addition, elections representing 535,063 shares were made pursuant to the notice of guaranteed delivery procedure, of which preliminary tabulations indicate 25,516 shares elected to receive cash, 267,764 shares elected to receive common units of MarkWest Energy Partners, and 241,783 elected to receive the stated consideration of 1.285 common units of MarkWest Energy Partners and $20.00 cash per share. Based on the preliminary tabulation of elections received prior to the deadline for submitting merger consideration election forms under the Redemption and Merger Agreement, the cash election is oversubscribed by less than one percent. As a result of the oversubscription, the elections will be subject to agreed-upon proration procedures described in the Redemption and Merger Agreement. MarkWest Hydrocarbon stockholders who elected to receive all of their merger consideration in cash will receive a combination of cash consideration and common unit consideration. However, the amount of the oversubscription and the exact allocation of the merger consideration will not be known until final results of the election process are determined at the end of the guaranteed delivery period described below. With respect to the elections that were made pursuant to the notice of guaranteed delivery procedure, which elections may be duplicative and supersede the prior election, such procedure requires the delivery of the share certificates representing such shares of MarkWest Hydrocarbon common stock (or a confirmation evidencing the book-entry transfer of such shares) to the exchange agent by 5:00 p.m., New York City time, on February 25, 2008. If the exchange agent does not receive the required stock certificates or confirmation by the guaranteed delivery deadline with respect to any such election, the shares of MarkWest Hydrocarbon common stock subject to such election will be treated as shares that did not make a valid election. After the final results of the merger consideration election process are determined following the expiration of the guaranteed delivery period, the actual merger consideration and the cash and common unit allocation will be computed using the formula contained in the Redemption and Merger Agreement. The formula will be based on, among other things, the actual number of shares of MarkWest Hydrocarbon common stock outstanding immediately prior to the completion of the transaction, the final results of the election process, and the volume weighted average price of MarkWest Energy Partners common units during the ten-day trading period ending Friday, February 15, 2008, of $32.25. A more complete description of the merger consideration and the proration procedures is contained in the Joint Proxy Statement/Prospectus dated January 7, 2008, that was first mailed to MarkWest equityholders on or about January 18, 2008. MarkWest equityholders are urged to read the Joint Proxy Statement/Prospectus carefully and in its entirety. Copies of the Joint Proxy Statement/Prospectus may be obtained free of charge by directing a request to the MarkWest investor relations department at 866-858-0482, by accessing the companies� website at www.markwest.com, or from the website of the Securities and Exchange Commission at www.sec.gov. MarkWest Energy Partners, L.P. (NYSE:MWE) is a publicly traded master limited partnership with a solid core of midstream assets and a growing core of gas transmission assets. It is one of the largest processors of natural gas in the Northeast and is the largest gas gatherer of natural gas in the prolific Carthage field in east Texas. It also has a growing number of other gas gathering and intrastate gas transmission assets in the Southwest, primarily in Texas and Oklahoma. MarkWest Hydrocarbon, Inc. (AMEX:MWP) controls and operates MarkWest Energy Partners, L.P. (NYSE:MWE), a publicly traded limited partnership engaged in the gathering, processing and transmission of natural gas; the transportation, fractionation and storage of natural gas liquids; and the gathering and transportation of crude oil. We also market natural gas and NGLs. This press release includes �forward-looking statements� within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended. All statements other than statements of historical facts included or incorporated herein may constitute forward-looking statements. Although we believe that the expectations reflected in the forward-looking statements, specifically those including those referring to future performance, growth, cash flow, operating income, distributable cash flow (DCF), distributions, or other factors, are reasonable, these forward-looking statements are not guarantees of future performance and we can give no assurance that such expectations will prove to be correct and that projected performance or distributions may not be achieved. Among the factors that could cause results to differ materially are those risks discussed in our joint proxy statement/prospectus, dated January 7, 2008, as filed with the SEC. You are also urged to carefully review and consider the cautionary statements and other disclosures, including those under the heading �Risk Factors,� made in the joint proxy statement/prospectus, which identify and discuss significant risks, uncertainties and various other factors that could cause actual results to vary significantly from those expressed or implied in the forward-looking statements. We do not undertake any duty to update any forward-looking statement. Investors and security holders are urged to read the joint proxy statement/prospectus carefully because it contains important information regarding MarkWest Energy Partners, MarkWest Hydrocarbon, and the transaction. Investors and security holders may obtain a free copy of the joint proxy statement/prospectus and other documents containing information about MarkWest Energy Partners and MarkWest Hydrocarbon, without charge, at the SEC�s website at www.sec.gov. Copies of the joint proxy statement/prospectus and the SEC filings that will be incorporated by reference in the joint proxy statement/prospectus may also be obtained free of charge by directing a request to the entities' investor relations department at 866-858-0482, or by accessing the companies� website at www.markwest.com. MarkWest Energy Partners, MarkWest Hydrocarbon, the officers and directors of the general partner of MarkWest Energy Partners, and the officers and directors of MarkWest Hydrocarbon may be deemed to be participants in the solicitation of proxies from their security holders. Information about these persons can be found in the Annual Report on Form 10-K/A for the year ended December 31, 2006, for each of MarkWest Energy Partners and MarkWest Hydrocarbon, as filed with the SEC, and additional information about such persons may be obtained from the joint proxy statement/prospectus. This document shall not constitute an offer to sell or the solicitation of an offer to buy any securities, nor shall there be any sale of securities in any jurisdiction in which such offer, solicitation, or sale would be unlawful prior to registration or qualification under the securities laws of any such jurisdiction. No offering of securities shall be made except by means of a prospectus meeting the requirements of the Securities Act of 1933, as amended.