 Targeting about 4% of Delaware's total state owned or managed building stock, the SEU bond issue included contractual guarantees of $148 million in savings which cut energy use in participating buildings by more than 25% for 20 years.The 2011 bond issue average payback period was almost 14 years and the longest maturity was 20 years, while average performance guarantees were greater than 20 years.SEUs present a different paradigm in energy governance, and they can present unique challenges.