Exhibit 99.10

PINNACLE WEST CAPITAL CORPORATION
NON-GAAP FINANCIAL MEASURE RECONCILIATION — OPERATING INCOME
(GAAP MEASURE) TO GROSS MARGIN (NON-GAAP FINANCIAL MEASURE)
(in thousands)

	THREE MONTHS ENDED
	JUNE 30,				Increase (Decrease)
	2007		2006		Pretax			After Tax
RECONCILIATION OF REGULATED ELECTRICITY SEGMENT GROSS MARGIN
Operating income (closest GAAP measure)	$	158,686	$	191,197	$	(32,511	)	$	(19,815	)
Plus:
Operations and maintenance		177,310		168,332		8,978			5,472
Real estate segment operations		46,174		98,412		(52,238	)		(31,839	)
Depreciation and amortization		92,835		89,297		3,538			2,156
Taxes other than income taxes		34,757		32,700		2,057			1,254
Other expenses		8,803		8,430		373			227
Marketing and trading fuel and purchased power		74,533		72,716		1,817			1,107
Less:
Real estate segment revenues		48,352		112,603		(64,251	)		(39,161	)
Other revenues		11,153		9,782		1,371			836
Marketing and trading revenues		92,637		89,925		2,712			1,653
Regulated electricity segment gross margin	$	440,956	$	448,774	$	(7,818	)	$	(4,766	)

	SIX MONTHS ENDED
	JUNE 30,				Increase (Decrease)
	2007		2006		Pretax			After Tax
RECONCILIATION OF REGULATED ELECTRICITY SEGMENT GROSS MARGIN
Operating income (closest GAAP measure)	$	226,675	$	248,360	$	(21,685	)	$	(13,217	)
Plus:
Operations and maintenance		348,888		346,759		2,129			1,298
Real estate segment operations		107,617		169,742		(62,125	)		(37,865	)
Depreciation and amortization		182,456		176,918		5,538			3,375
Taxes other than income taxes		69,476		68,273		1,203			733
Other expenses		17,291		16,952		339			207
Marketing and trading fuel and purchased power		132,477		146,891		(14,414	)		(8,785	)
Less:
Real estate segment revenues		125,602		220,457		(94,855	)		(57,814	)
Other revenues		20,516		21,006		(490	)		(299	)
Marketing and trading revenues		165,108		174,927		(9,819	)		(5,985	)
Regulated electricity segment gross margin	$	773,654	$	757,505	$	16,149		$	9,844