There is, an inverter sized for the load with an auto transfer switch attached to a set of 100ah batteries will do what you're looking for. And that is what a U

There is, an inverter sized for the load with an auto transfer switch attached to a set of 100ah batteries will do what you're looking for. And that is what a UPS is on the inside. They just tend to use terribly small batteries. Such setups are easy to build if you want it and running a 100-200w blower doesn't require too many batteries either. However, if you need to run a compressor, the number of batteries required to power that for 6hours would start to get cost prohibitive. https://www.amazon.com/s?k=2000w+pure+sine+wave+inverter+auto+transfer+switch https://www.amazon.com/s?k=2000w+pure+sine+wave+inverter+aut... https://www.amazon.com/s?k=220v+automatic+transfer+switch+50amp https://www.amazon.com/s?k=220v+automatic+transfer+switch+50... https://www.amazon.com/s?k=100ah+lifepo4+battery https://www.amazon.com/s?k=100ah+lifepo4+battery This guy has accumulated essentially everything you could want to know about such setups, at any voltage, any reasonable power range, in various applications: backup systems, full off-grid, mobile power. https://www.youtube.com/@WillProwse https://www.youtube.com/@WillProwse https://www.mobile-solarpower.com/ https://www.mobile-solarpower.com/ For a 240v load, there are inverters that output 220v or you can use one inverter to power each hot line, just buy the batteries at the same time from the same manufacturer and ensure they will stay balanced. In your case you could also use a cheaper manual transfer switch if you don't mind going into the closet to flip it when the power goes out.