X0306 4 2016-01-20 0 0001549922 Summit Midstream Partners, LP SMLP 0001558915 ENERGY CAPITAL PARTNERS II, LLC 51 JOHN F. KENNEDY PARKWAY SUITE 200 SHORT HILLS NJ 07078 1 0 1 0 See Remarks 0001456360 ENERGY CAPITAL PARTNERS II, LP 51 JOHN F. KENNEDY PARKWAY SUITE 200 SHORT HILLS NJ 07078 0 0 1 0 0001456364 ENERGY CAPITAL PARTNERS II-A, LP 51 JOHN F. KENNEDY PARKWAY SUITE 200 SHORT HILLS NJ 07078 0 0 1 0 0001558920 ENERGY CAPITAL PARTNERS II-B IP, LP 51 JOHN F. KENNEDY PARKWAY SUITE 200 SHORT HILLS NJ 07078 0 0 1 0 0001558930 ENERGY CAPITAL PARTNERS II-C (SUMMIT IP), LP 51 JOHN F. KENNEDY PARKWAY SUITE 200 SHORT HILLS NJ 07078 0 0 1 0 0001532708 Energy Capital Partners II (Summit Co-Invest), LP 51 JOHN F. KENNEDY PARKWAY SUITE 200 SHORT HILLS NJ 07078 0 0 1 0 COMMON UNITS (LIMITED PARTNER INTERESTS) 2016-01-20 4 P 0 57614 14.58 A 1059347 I BY: SMLP HOLDINGS, LLC COMMON UNITS (LIMITED PARTNER INTERESTS) 2016-01-21 4 P 0 30901 15.12 A 1090248 I BY: SMLP HOLDINGS, LLC COMMON UNITS (LIMITED PARTNER INTERESTS) 2016-01-21 4 P 0 76075 14.71 A 1166323 I BY: SMLP HOLDINGS, LLC COMMON UNITS (LIMITED PARTNER INTERESTS) 2016-01-22 4 P 0 44492 16.39 A 1210815 I BY: SMLP HOLDINGS, LLC COMMON UNITS (LIMITED PARTNER INTERESTS) 151160 I BY: SUMMIT MIDSTREAM PARTNERS, LLC COMMON UNITS (LIMITED PARTNER INTERESTS) 5293571 I BY: SUMMIT MIDSTREAM PARTNERS HOLDINGS, LLC Units were purchased pursuant to a 10b5-1 plan entered into on December 15, 2015. These common units were purchased in multiple transactions ranging from $14.23 to $14.95, inclusive. The price reported in Column 4 is a weighted average price. The Reporting Persons undertake to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of common units purchased at each separate price within the ranges set forth in footnotes 2, 4, 5 and 6. These common units were purchased in multiple transactions ranging from $15.10 to $15.17, inclusive. These common units were purchased in multiple transactions ranging from $14.10 to $15.08, inclusive. These common units were purchased in multiple transactions ranging from $15.89 to $16.78, inclusive. Energy Capital Partners II, LP (''ECP II''), Energy Capital Partners II-A, LP (''ECP II-A''), Energy Capital Partners II-B (SMLP IP), LP (''ECP II-B SMLP IP'') and Energy Capital Partners II-C (SMLP IP), LP (''ECP II-C SMLP IP'' and together with ECP II, ECP II-A and ECP II-B SMLP IP the ''SMLP Holdings Owners'') collectively hold all of the membership interests in SMLP Holdings, LLC (''SMLP Holdings''). Energy Capital Partners II, LLC (''ECP'') indirectly controls the SMLP Holdings Owners. Accordingly, ECP and the SMLP Holdings Owners may be deemed to indirectly beneficially own the 1,210,815 common units held by SMLP Holdings but disclaim beneficial ownership except to the extent of their pecuniary interest therein. ECP II, ECP II-A, Energy Capital Partners II-B IP, LP (''ECP II-B''), Energy Capital Partners II-C (Summit IP), LP (''ECP II-C''), Energy Capital Partners II (Summit Co-Invest), LP ("ECP Summit Co-Invest" and together with ECP II, ECP II-A, ECP II-B and ECP II-C, the ''ECP Funds''), collectively hold greater than a majority of the membership interest in Summit Midstream Partners, LLC ("Summit") and are entitled to elect five of the five directors of Summit. Summit is the sole member of Summit Midstream Partners Holdings, LLC (''SMPH'') and as such, may be deemed to have indirect beneficial ownership of the 5,293,571 common units held by SMPH in addition to the 151,160 common units held directly. Accordingly, ECP and the ECP Funds may be deemed to indirectly beneficially own the 5,444,731 common units held by Summit and SMPH but disclaim beneficial ownership except to the extent of their pecuniary interest therein. The common units do not include 24,409,850 subordinated units held by SMPH. The subordinated units may be converted into common units on a one-for-one basis upon the termination of the subordination period as set forth in the Issuer Partnership Agreement. Energy Capital Partners II, LP By: Energy Capital Partners GP II, LP Its: General Partner By: Energy Capital Partners II, LLC Its: General Partner By: /s/ Enoch O. Varner, Counsel 2016-01-22 Energy Capital Partners II-A, LP By: Energy Capital Partners GP II, LP Its: General Partner By: Energy Capital Partners II, LLC Its: General Partner By: /s/ Enoch O. Varner, Counsel 2016-01-22 Energy Capital Partners II-B IP, LP By: Energy Capital Partners GP II, LP Its: General Partner By: Energy Capital Partners II, LLC Its: General Partner By: /s/ Enoch O. Varner, Counsel 2016-01-22 Energy Capital Partners II-C (Summit IP), LP By: Energy Capital Partners GP II, LP Its: General Partner By: Energy Capital Partners II, LLC Its: General Partner By: /s/ Enoch O. Varner, Counsel 2016-01-22 Energy Capital Partners II (Summit Co-Invest), LP By: Energy Capital Partners GP II Co-Investment (Summit), LLC Its: General Partner By: Energy Capital Partners II, LLC Its: Managing Member By: /s/ Enoch O. Varner, Counsel 2016-01-22 Energy Capital Partners II, LLC By: /s/ Enoch O. Varner, Counsel 2016-01-22