This paper presents a valuation study of hydropower investment opportunities in the Norwegian context. According to NVE (Norwegian Water Resources and Energy Directorate, the regulator), there is a potential of 39 TWh not yet developed (generation in a normal year is approximately 120 TWh). By using the conceptual real option framework of Dixit and Pindyck [1994. Investment Under Uncertainty. Princeton University Press, Princeton, NJ] one can estimate the value of investment opportunities to NOK 11 million/GWh (EUR 1.4 million/GWh). Furthermore, the optimal trigger price for initiating an investment based on electricity forward prices is calculated to NOK 0.32/kWh (EUR 0.04/kWh). The analysis shows consistency between real option theory and aggregate investment behaviour in Norwegian hydropower. (C) 2007 Elsevier Ltd. All rights reserved.