Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Comparison of Predicted to Measured Module Performance.



Arthur H. Fanney, Brian P. Dougherty, Mark W. Davis


Computer simulation models to accurately predict the electrical performance of photovoltaic modules are essential. Without such models, potential purchasers of photovoltaic systems have insufficient information to judge the relative merits and cost effectiveness of photovoltaic systems. The purpose of this paper is to compare the predictions of a simulation model, developed by Sandia National Laboratories, to measurements from photovoltaic modules installed in a vertical wall facade in Gaithersburg, MD. The photovoltaic modules were fabricated using monocrystalline, polycrystalline, tandem-junction amorphous, and copper-indium diselenide cells. Polycrystalline modules were constructed using three different glazing materials - 6 mm low-iron glass, 2 mm ethylene-tetrafluoroethylene copolymer (ETFE), and 2 mm polyvinylidene fluoride (PVDF). In order to only assess the simulation model's ability to predict photovoltaic module performance, measured solar radiation data in the plane of the modules is initially used. Additional comparisons are made using horizontal radiation measurements. The ability of the model to accurately predict the temperature of the photovoltaic cells is investigated by comparing predicted energy production using measured versus predicted photovoltaic cell temperatures. The model was able to predict the measured annual energy production of the photovoltaic modules, with the exception of the tandem-junction amorphous modules, to within 6% using vertical irradiance measurements. The model overpredicted the annual energy production by approximately 14% for the tandem-junction amorphous panels. Using measured horizontal irradiance as input to the simulation model, the agreement between measured and predicted annual energy predictions varied between 1% and 8%, again with the exception of the tandem-junction amorphous silicon modules. The large difference between measured and predicted results for the tandem-junction modules is attributed to performance
Proceedings Title
Energy Sustainability (ES2007). Session: 11-2 Solar Power Testing. Proceedings
Conference Dates
June 27-30, 2007
Conference Location
Long Beach, CA


computer simulation, photovaltaic module, specifications, parameters, irradiance, temperature, radiation measurements


Fanney, A. , Dougherty, B. and Davis, M. (2007), Comparison of Predicted to Measured Module Performance., Energy Sustainability (ES2007). Session: 11-2 Solar Power Testing. Proceedings, Long Beach, CA, [online], (Accessed June 23, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created June 27, 2007, Updated February 17, 2017