The specialist tank, known as a VIE (Vacuum Insulated Evaporator), holds two and a half million litres of oxygen and is due to be fully operational on Monday.
The oxygen will be piped round the hospital so that more Covid-19 patients can be treated in the county.
This will reduce the need for acute hospital admission, and support patients to return to the county from District General Hospitals for their continued care.
Powys Teaching Health Board Medical Director Wyn Parry said, “Our Five Point Plan for coronavirus includes the expansion of the skills and services available in our community hospitals.”
“The VIE oxygen tank is a critical part of this. It will allow us to provide oxygen therapy for patients at Breconshire War Memorial Hospital.
“One of the typical features of Covid-19 is hypoxemia – or low oxygen in the blood. Providing patients with supplemental oxygen using oxygen therapy helps to ensure that the right amounts of oxygen are getting into the bloodstream.”
“This is a central element of therapy and helps to ensure that patients remain stable and can be cared for locally.”