Based on an original dataset of 651 households in the informal settlement of Kibera in Nairobi, Kenya, this article examines household electricity use, drivers of uptake and willingness to pay (WTP) for efficient compact fluorescent lamp (CFL) lighting technology. Informal and illegal electricity consumption, euphemistically referred to by residents as "electricity borrowing", is common. This removes the metered electricity price lever upon which to influence consumer behaviour and demand for energy-efficient technologies. However, as this study demonstrates, the comparative durability of efficient lighting technologies presents economic benefits for uptake even in a context of fixed-rate electricity payments. While bulb uptake and stated WTP are independent of demographic characteristics such as income activity, gender, education and other factors, they are significantly correlated with informal electricity consumption, beliefs related to bulb durability, knowledge of past energy efficiency outreach, and other contextual factors, underlining a need for tailored approaches to energy efficiency in informal settlements.