{"id":8616,"date":"2021-11-25T05:28:57","date_gmt":"2021-11-25T05:28:57","guid":{"rendered":"https:\/\/www.elgi.com\/eu\/?post_type=wiki&#038;p=8616"},"modified":"2026-04-21T06:34:12","modified_gmt":"2026-04-21T06:34:12","slug":"fixed-or-variable-compressors","status":"publish","type":"wiki","link":"https:\/\/www.elgi.com\/eu\/wiki\/fixed-or-variable-compressors\/","title":{"rendered":"Why to choose for a variable speed compressor vs. fixed speed compressor?"},"content":{"rendered":"<p>Having participated in hundreds of projects around <strong>compressed air<\/strong>, the question why to choose for a variable speed compressor vs. a fixed speed compressor is one of the most difficult questions to answer and surely one of the main of customers in all industries, ranging from <a href=\"https:\/\/www.elgi.com\/eu\/air-compressor-food-beverage\/\">Food &#038; Beverage<\/a>, <a href=\"https:\/\/www.elgi.com\/eu\/air-compressor-automotive\/\">Automotive<\/a>, General Manufacturing, etc. The answer depends on energy efficiency of the <strong>compressed air<\/strong> system, the cost of maintenance and the initial investment for the next 10 years. <\/p>\r\n<p>The answer to this question is not obvious in the case of a new installation, since there is no consumption history that can be studied to be able to categorically state &#8220;the best thing for you is a variable speed compressor &#8221; or &#8220;the best thing for you is a <a href=\"https:\/\/www.elgi.com\/eu\/air-compressor-resources\/variable-frequency-drive-vs-fixed-speed-drive\/\">fixed speed compressor<\/a>&#8220;. There are different theories that claim that, if there is any uncertainty about compressed air consumption, the most efficient would be a variable speed compressor, but I ask myself: to what extent is this true? Will it be valid? In the graph below we see the study of energy efficiency between a variable speed compressor and a fixed speed compressor similar to the power of a typical manufacturer:<\/p>\r\n<div class=\"row\">\r\n   <aside class=\"col-md-6\"><img loading=\"lazy\" decoding=\"async\" title=\"CTP\" src=\"https:\/\/www.elgi.com\/eu\/wp-content\/uploads\/2021\/11\/elgi-wiki-img1.png\" alt=\"CTP\" width=\"1079\" height=\"521\" class=\"img-fluid\" \/><\/aside>\r\n   <aside class=\"col-md-6\">\r\n      <p>The last part of the graph shows how the two curves intersect and it turns out that a fixed speed compressor with an average utilisation above 94% would be more efficient than a variable speed compressor. However, if the usage is less than 94%, then the <a href=\"https:\/\/www.elgi.com\/eu\/air-compressor-resources\/variable-frequency-drive-vs-fixed-speed-drive\/\">variable speed compressor<\/a> would be the solution that would save more energy for the same flow of compressed air consumed.<\/p>\r\n   <\/aside>\r\n   <!-- <aside class=\"col-md-3\"><\/aside> -->\r\n<\/div>\r\n<p><\/p>\r\n<p>With this information we could help our customer by claiming that a variable speed compressor would be more efficient with 94% certainty, although there are other possibilities which raise further questions: what if we used two compressors at an industrial plant to provide all the compressed air flow required? Would this be a more or less effective combination for the compressed air system? This is another big question and to answer it I carried out the following study with different combinations of industrial compressors from the same manufacturer for a total compressed air power of 110 kW.<\/p>\r\n<div class=\"row\">\r\n   <aside class=\"col-md-6\"><img loading=\"lazy\" decoding=\"async\" title=\"CTP\" src=\"https:\/\/www.elgi.com\/eu\/wp-content\/uploads\/2021\/11\/elgi-wiki-img2.png\" alt=\"CTP\" width=\"831\" height=\"539\" class=\"img-fluid\" \/><\/aside>\r\n   <aside class=\"col-md-6\">\r\n      <p>The graph gives us the following results on the best energy efficiency of the <strong>compressed air<\/strong> system for the same consumption rate:<\/p>\r\n      <img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/www.elgi.com\/eu\/wp-content\/uploads\/2021\/11\/elgi-wiki-img3.png\" width=\"834\" height=\"283\" class=\"img-fluid\">\r\n   <\/aside>\r\n   <!-- <aside class=\"col-md-3\"><\/aside> -->\r\n<\/div>\r\n<p><\/p>\r\n<p>In conclusion, if we do not know the average flow rate that we are going to consume, we have a 70% probability of obtaining the best energy efficiency if our compressed air system consists of a fixed speed compressor accompanied by a variable speed compressor. The rest of the options may also be viable, but the chances of getting the best energy efficiency in the entire system are much lower.<\/p>\r\n<p>When a compressed air system is required, it is always good to have an expert who can advise and help define the complete system.<\/p>\r\n<p>Questions about compressed air? Do not hesitate to contact us at  <a href=\"mailto:euenquiry@elgi.com\" rel=\"noopener\" target=\"_blank\">euenquiry@elgi.com<\/a>.<\/p>","protected":false},"featured_media":8173,"template":"","categories":[139],"class_list":["post-8616","wiki","type-wiki","status-publish","has-post-thumbnail","hentry","category-knowledge-center"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/www.elgi.com\/eu\/wp-json\/wp\/v2\/wiki\/8616","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.elgi.com\/eu\/wp-json\/wp\/v2\/wiki"}],"about":[{"href":"https:\/\/www.elgi.com\/eu\/wp-json\/wp\/v2\/types\/wiki"}],"version-history":[{"count":1,"href":"https:\/\/www.elgi.com\/eu\/wp-json\/wp\/v2\/wiki\/8616\/revisions"}],"predecessor-version":[{"id":51698,"href":"https:\/\/www.elgi.com\/eu\/wp-json\/wp\/v2\/wiki\/8616\/revisions\/51698"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.elgi.com\/eu\/wp-json\/wp\/v2\/media\/8173"}],"wp:attachment":[{"href":"https:\/\/www.elgi.com\/eu\/wp-json\/wp\/v2\/media?parent=8616"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.elgi.com\/eu\/wp-json\/wp\/v2\/categories?post=8616"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}