QuickLinks -- Click here to rapidly navigate through this document

Exhibit 12.1

MarkWest Energy Partners, L.P.
Calculation of Earnings to Fixed Charges
(Dollar amounts in thousands)

	2007			2008			2009			2010			2011
Total fixed charges	$	49,191		$	86,559		$	112,981		$	120,711		$	123,893
Earnings:
Earnings from continuing operations before income taxes	$	(59,155	)	$	273,602		$	(155,370	)	$	34,291		$	119,894
Add:
Fixed charges		49,191			86,559			112,981			120,711			123,893
Amortization of capitalized interest		478			1,110			1,444			1,583			1,639
Cash distributions from equity method investments		10,840			445			—			2,508			300
(Income) Loss from equity method investments		(5,309	)		(90	)		(3,505	)		(1,562	)		1,095
Subtract:
Interest capitalized		(3,344	)		(9,486	)		(12,228	)		(2,766	)		(1,121	)
Total earnings	$	(7,299	)	$	352,140		$	(56,678	)	$	154,765		$	245,700
Ratio		(0.15	)		4.07			(0.50	)		1.28			1.98
Deficit	$	(56,490	)	$	—		$	(169,659	)	$	—		$	—

QuickLinks

Exhibit 12.1

MarkWest Energy Partners, L.P. Calculation of Earnings to Fixed Charges (Dollar amounts in thousands)