The federal market has been a source of strong energy service company (ESCO) industry growth over the last decade as traditional "MUSH" markets – municipal/state governments, universities, schools and hospitals – have matured. Federal alternative financing programs – Utility Energy Services Contracts (UESC) and Department of Energy (DOE) Super, Army and Air Force Energy Savings Performance Contracts (ESPC) – have enabled this growth, but recent events threaten the ESPC programs. We compare the federal and MUSH markets by analyzing ~1550 completed projects and interviewing ESCO representatives. Federal ESPC market activity is estimated at ~$1.6 billion (B) over 10-15 years; activity in 2002 was ~$230 million (M). MUSH markets have produced ~ $12-16B in projects over 20 years, and ~$0.8-1.0B in 2002. Federal sector projects have longer average contract terms than MUSH (14 vs. 9.5 years respectively). Federal projects are larger (median costs are $1.85M vs. $0.98M for MUSH), but costs per square foot are lower (median costs are $2.08/ft vs. $2.93/ft for MUSH), and annual energy savings are higher (18 vs. 14 kBtu/ft). Non-energy savings are more often counted in federal projects (58% vs. 35% of MUSH projects) but when counted represent a higher proportion of savings in MUSH projects. Median payback times in the federal market are shorter than MUSH (7.7 vs. 8.8 years) and calculated net economic benefits of 214 federal projects amount to ~$550M, compared to ~$1.2B for 965 MUSH projects.