--- description: What is Efficiency (η)? It is the proportion of usable energy leaving a machine to energy entering it. It is expressed as a percentage. title: What is Efficiency (η)? - Energy Theory image: https://energytheory.com/wp-content/uploads/2023/04/What-is-Efficiency.jpg --- [ Close Menu ](#) * [About](https://energytheory.com/about-us/) * [EV](https://energytheory.com/category/electric-vehicles/) * [FAQs](https://energytheory.com/category/faqs/) * [Glossary](https://energytheory.com/category/glossary/) * [Green](https://energytheory.com/category/green/) * [Renewable](https://energytheory.com/category/renewable/) * [Sustainable](https://energytheory.com/category/sustainable/) * [Energy Economy](https://energytheory.com/category/energy-economy/) * [Energy Services](https://energytheory.com/category/energy-services/) * [Solar](https://energytheory.com/category/solar/) * [Sustainable](https://energytheory.com/category/sustainable/) * [News](https://energytheory.com/category/latest-news/) * [Language](#) [ ![Energy Theory](https://energytheory.com/wp-content/uploads/2022/11/2e3rtgthghnm.png) ](https://energytheory.com/ "Energy Theory") ![en](https://cdn.gtranslate.net/flags/svg/en.svg)English [![es](https://cdn.gtranslate.net/flags/svg/es.svg) Spanish](#) [![fr](https://cdn.gtranslate.net/flags/svg/fr.svg) French](#) [![en](https://cdn.gtranslate.net/flags/svg/en.svg) English](#) [![it](https://cdn.gtranslate.net/flags/svg/it.svg) Italian](#) [![zh-CN](https://cdn.gtranslate.net/flags/svg/zh-CN.svg) Chinese (Simplified)](#) [![nl](https://cdn.gtranslate.net/flags/svg/nl.svg) Dutch](#) [![fi](https://cdn.gtranslate.net/flags/svg/fi.svg) Finnish](#) [![de](https://cdn.gtranslate.net/flags/svg/de.svg) German](#) [![hi](https://cdn.gtranslate.net/flags/svg/hi.svg) Hindi](#) [![ja](https://cdn.gtranslate.net/flags/svg/ja.svg) Japanese](#) [![pl](https://cdn.gtranslate.net/flags/svg/pl.svg) Polish](#) [![pt](https://cdn.gtranslate.net/flags/svg/pt.svg) Portuguese](#) [![ru](https://cdn.gtranslate.net/flags/svg/ru.svg) Russian](#) [ ![Energy Theory](https://energytheory.com/wp-content/uploads/2022/11/2e3rtgthghnm.png) ](https://energytheory.com/ "Energy Theory") ![en](https://cdn.gtranslate.net/flags/svg/en.svg)English [![es](https://cdn.gtranslate.net/flags/svg/es.svg) Spanish](#) [![fr](https://cdn.gtranslate.net/flags/svg/fr.svg) French](#) [![en](https://cdn.gtranslate.net/flags/svg/en.svg) English](#) [![it](https://cdn.gtranslate.net/flags/svg/it.svg) Italian](#) [![zh-CN](https://cdn.gtranslate.net/flags/svg/zh-CN.svg) Chinese (Simplified)](#) [![nl](https://cdn.gtranslate.net/flags/svg/nl.svg) Dutch](#) [![fi](https://cdn.gtranslate.net/flags/svg/fi.svg) Finnish](#) [![de](https://cdn.gtranslate.net/flags/svg/de.svg) German](#) [![hi](https://cdn.gtranslate.net/flags/svg/hi.svg) Hindi](#) [![ja](https://cdn.gtranslate.net/flags/svg/ja.svg) Japanese](#) [![pl](https://cdn.gtranslate.net/flags/svg/pl.svg) Polish](#) [![pt](https://cdn.gtranslate.net/flags/svg/pt.svg) Portuguese](#) [![ru](https://cdn.gtranslate.net/flags/svg/ru.svg) Russian](#) [Glossary](https://energytheory.com/category/glossary/) # What is Efficiency (η)? By [Elliot Clark](https://energytheory.com/author/elliot%5Fclark/)November 17, 20233 Mins Read ![What is Efficiency \(η\)?](https://energytheory.com/wp-content/uploads/2023/04/What-is-Efficiency-1024x683.jpg "What is Efficiency (η)?") Efficiency (η) is the proportion of usable energy leaving a machine to energy entering it; it is typically expressed as a percentage. The more sunlight will be turned into electrical energy by solar panels the more efficient they are. High efficiency solar panels are more expensive but require less space, making them a good option for homeowners with small roof spaces. Photovoltaic (PV) cell efficiency, based on silicon type and cell design, and **total panel efficiency**, based on cell layout, configuration, and panel area, are the two primary determinants of solar panel efficiency. By creating a larger surface area to catch the sunlight, increasing the panel size can also increase efficiency. The most potent solar panels can now produce up to 700W of electricity. The two factors, PV Cell efficiency and Panel efficiency are described further below: **Photovoltaic (PV) Cell Efficiency** The cell structure and the substrate used—which is typically either P-type silicon or N-type silicon—determine the efficacy of the cell. The **fill factor** (FF), which is the highest conversion efficiency of a PV cell at the best operating voltage and current, is used to determine cell efficiency. The efficiency (η) of the panel is significantly influenced by the cell architecture. The silicon variety, [busbar](https://energytheory.com/what-is-a-busbar/) configuration, junction, and passivation type are important characteristics. Due to the high purity N-type silicon substrate and the absence of busbar shading losses, panels constructed using expensive **IBC cells presently have the highest efficiency** (21-23%). However, panels made with the most recent monocrystalline PERC, N-Type TOPCON, and advanced heterojunction (HJT) cells have efficiency values that are significantly higher than 21%. **Also Read:** [What is an Electrochemical Cell?](https://energytheory.com/what-is-an-electrochemical-cell/) **Panel Efficiency** Under standard test circumstances (STC), a solar panel’s efficiency is calculated using a cell temperature of 25°C, [solar irradiance](https://www.nasa.gov/mission%5Fpages/sdo/science/solar-irradiance.html) of 1000W/m2, and an air mass of 1.5. The maximum power rating, or Pmax (W) at STC, is effectively determined by **dividing the total panel area**, expressed in square meters, by the efficiency (%) of the panel. Numerous variables, such as temperature, irradiance level, cell type, and cell interconnection, can affect the overall effectiveness of a panel. The most effective panels are those made with cutting-edge Interdigitated back contact or IBC cells, which are followed by heterojunction (HJT) cells, TOPcon cells, half-cut and multi-busbar monocrystalline PERC cells, shingled cells, and 60-cell (4-5 busbar) mono cells. The least effective and least expensive panels are typically 60-cell polycrystalline or multicrystalline panels. Share. 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With a background in environmental science, he has a deep understanding of the issues facing our planet and is committed to educating others on how they can make a difference. #### Related Posts [![Post-consumer recycled (PCR) content](https://energytheory.com/wp-content/uploads/2024/04/Post-consumer-recycled-PCR-content.png "What is Post-Consumer Recycled (PCR) Content?")](https://energytheory.com/what-is-post-consumer-recycled-pcr-content/ "What is Post-Consumer Recycled (PCR) Content?") #### [What is Post-Consumer Recycled (PCR) Content?](https://energytheory.com/what-is-post-consumer-recycled-pcr-content/) April 9, 2024 [![Heating Seasonal Performance Factor (HSPF)](https://energytheory.com/wp-content/uploads/2024/02/Heating-Seasonal-Performance-Factor-HSPF.jpg "What is Heating Seasonal Performance Factor (HSPF)?")](https://energytheory.com/what-is-heating-seasonal-performance-factor-hspf/ "What is Heating Seasonal Performance Factor (HSPF)?") #### [What is Heating Seasonal Performance Factor (HSPF)?](https://energytheory.com/what-is-heating-seasonal-performance-factor-hspf/) February 3, 2024 [![What is Annual Fuel Utilization Efficiency (AFUE)](https://energytheory.com/wp-content/uploads/2024/02/What-is-Annual-Fuel-Utilization-Efficiency-AFUE.jpg "What is Annual Fuel Utilization Efficiency (AFUE)?")](https://energytheory.com/what-is-annual-fuel-utilization-efficiency-afue/ "What is Annual Fuel Utilization Efficiency (AFUE)?") #### [What is Annual Fuel Utilization Efficiency (AFUE)?](https://energytheory.com/what-is-annual-fuel-utilization-efficiency-afue/) February 2, 2024 [Add A Comment ](#) Leave A Reply [Cancel Reply](https://energytheory.com/what-is-efficiency-%CE%B7/#respond) Save my name, email, and website in this browser for the next time I comment. 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