IEA Reports: PV Systems Recover Embedded Costs in 1.6 to 3.3 Years

September 05, 2006 by Jeff Shepard

The International Energy Agency (IEA) is reporting that rooftop solar photovoltaic (PV) systems recover their energy content (from manufacturing and recycling) within 1.6 to 3.3 years, depending on location. Although solar electricity is pollution-free, PV systems require a certain amount of energy which must be 'reimbursed' before they can be considered as renewable and clean, according to "Compared assessment of selected environmental indicators of photovoltaic electricity in OECD cities" an assessment by IEA's Photovoltaic Power Systems Program. The energy is needed to manufacture and install PV systems and, later, dismantle and recycle them.

PV systems mounted on rooftops produce the amount of energy needed to recover their energy content in the range of 1.6 to 3.3 years, and generate (during their service life) between 17.9 and 8 times their initial energy content. Once they have reimbursed their initial energy input, rooftop PV systems can avoid the emission of 40 tons of CO2, depending on their location and on the local electricity mix available. The report was prepared in order to provide "clear and well-documented answers to politicians, decision-makers and the general public about what PV can and cannot achieve in terms of renewable, clean energy production and environmental protection.".

The results for solar PV facades are slightly worse than for roof-top PV systems since they generate less energy for the same installed capacity. They produce the amount of energy to recover their energy content within 2.7 to 4.7 years, and produce (during their service life) between 10.1 and 5.4 times their initial energy content. The contribution of PV facades to CO2 emissions mitigation can be up to 23 tons of CO2 per kW installed.

The energy payback time (EPBT) and energy return factor (ERF) depend on the location of the PV installation, and the performance of PV systems is assessed on a country-by-country basis in the report, and on a city-by-city approach in larger countries "where the potential for urban-scale integrated PV is highest with a view to both better reflect the varying reality and to facilitate the use of the results at national and local levels." The global range for 41 cities in 26 OECD countries are examined, and the data "clearly demonstrate how beneficial urban-scale PV systems are for reducing the use of highly-polluting conventional energy sources and for contributing to improving the general efficiency of large cities wherever they are located worldwide." Country results can be used to "raise the awareness of politicians and decision-makers at national level in order to accelerate the development and the deployment of PV technologies in a given country."

The study examines only grid-connected PV-systems that are made of mainstream components available on the market (standard multi-crystalline silicon modules and standard grid-tied inverters) and architecturally integrated in buildings. The average lifetime of PV modules is estimated at 30 years, although actual power production from the modules is generally over 25 years while the inverter (the "weakest part of a grid-connected PV system") is ten years.