This paper describes data and algorithms to estimate typical average interior illuminance from daylighting using a hybrid of Hay, Davies, Klucher, Reindl (HDKR) method for calculating total solar radiation on a tilted surface and the Illuminating Engineering Society (IES) Lumen Method for estimating interior illuminance from daylighting. This hybrid algorithm, in conjunction with typical meteorological data, directly accounts for shading and typical local cloud cover effects on an hour-by-hour basis, which is difficult to do using the IES sky-cover or sky-ratio methods. Several experiments show reasonable agreement between measured and calculated results. Case study examples demonstrate of use of the method, when incorporated into software, to quickly analyze daylighting potential in industrial facilities, and the use of this information to develop specific recommendations for cost-effectively reducing lighting energy use in industrial facilities by improving the utilization of natural lighting.