MarkWest Energy Partners Announces Sale of Common Units under Equity Distribution Agreement

  MarkWest Energy Partners Announces Sale of Common Units under Equity
  Distribution Agreement

Business Wire

DENVER -- December 17, 2013

MarkWest Energy Partners, L.P. (NYSE: MWE) (“MarkWest”) announced today that
it has agreed to sell approximately 4,750,000 common units pursuant to a terms
agreement under its equity distribution agreement with Citigroup Global
Markets Inc. (the “Sales Agent”) for total gross proceeds of approximately
$301.15 million. In addition, 250,000 common units will be sold by M&R MWE
Liberty, LLC (the “Selling Unitholder”). MarkWest has granted the Sales Agent
a 30-day option to purchase a maximum of 712,500 additional common units, and
the Selling Unitholder has granted the Sales Agent a 30-day option to purchase
a maximum of 37,500 additional common units. MarkWest intends to use the net
proceeds of this offering for general partnership purposes, which may include,
among other things paying or refinancing a portion of its outstanding
indebtedness and funding working capital, its capital expenditure program or
acquisitions. MarkWest will not receive any of the proceeds from the sale of
common units by the Selling Unitholder. The offering is expected to close on
December 23, 2013.

The Sales Agent may offer the common units from time to time in one or more
transactions on the New York Stock Exchange, in the over-the-counter market,
through negotiated transactions or otherwise at market prices or negotiated
prices.

The offering is being made pursuant to an effective registration statement on
Form S-3 previously filed with the Securities and Exchange Commission. Copies
of the prospectus supplement, the accompanying base prospectuses and the free
writing prospectus related to this offering may be obtained from Citigroup
Global Markets Inc., c/o Broadridge Financial Solutions, 1155 Long Island
Avenue, Edgewood, NY 11717 (tel: 800-831-9146).

This press release shall not constitute an offer to sell or the solicitation
of an offer to buy, nor shall there be any sale of the securities described
above in any state or jurisdiction in which such offer, solicitation, or sale
would be unlawful prior to registration or qualification under the securities
laws of such state or jurisdiction.

MarkWest Energy Partners, L.P. is a master limited partnership engaged in the
gathering, transportation, and processing of natural gas; the transportation,
fractionation, marketing, and storage of natural gas liquids; and the
gathering and transportation of crude oil. MarkWest has extensive natural gas
gathering, processing, and transmission operations in the southwest, Gulf
Coast, and northeast regions of the United States, including the Marcellus
Shale, and is the largest natural gas processor and fractionator in the
Appalachian region.

This press release includes “forward-looking statements.” All statements other
than statements of historical facts included or incorporated herein may
constitute forward-looking statements. Actual results could vary significantly
from those expressed or implied in such statements and are subject to a number
of risks and uncertainties. Although MarkWest believes that the expectations
reflected in the forward-looking statements are reasonable, MarkWest can give
no assurance that such expectations will prove to be correct. The
forward-looking statements involve risks and uncertainties that affect
operations, financial performance, and other factors as discussed in filings
with the Securities and Exchange Commission. Among the factors that could
cause results to differ materially are those risks discussed in the periodic
reports filed with the SEC, including MarkWest’s Annual Report on Form 10-K
for the year ended December 31, 2012 and its Quarterly Reports on Form 10-Q
for the quarters ended March 31, 2013, June 30, 2013 and September 30, 2013.
You are urged to carefully review and consider the cautionary statements and
other disclosures made in those filings, specifically those under the heading
“Risk Factors.” MarkWest does not undertake any duty to update any
forward-looking statement except as required by law.

Contact:

MarkWest Energy Partners, L.P.
Frank Semple, 866-858-0482
Chairman, President & CEO
or
Nancy Buese, 866-858-0482
Executive VP & CFO
or
Josh Hallenbeck, 866-858-0482
VP of Finance & Treasurer
investorrelations@markwest.com