Is liquid oxygen cheaper than a PSA plant?

Assist International, on Open Critical Care, says liquid oxygen is generally more expensive than PSA because of equipment, supporting infrastructure and distribution, with costs falling over time for very large systems.

Does a PSA plant remove all cylinder costs?

No. WHO interim guidance (2020) called it best practice to keep cylinders as a backup supply for a PSA plant, so some cylinder costs remain.

What running costs does a PSA plant have?

Global Fund guidance lists spare parts, scheduled maintenance, repairs, electricity, diesel, distribution and staff salaries.

On-site oxygen vs delivered oxygen: how do costs compare?

Q: On-site oxygen vs delivered oxygen: how do costs compare?

On-site oxygen costs include the plant and its running (electricity, maintenance, spare parts, staff), while delivered oxygen costs include recurring payments for gas, cylinder or tank rental and transport, plus losses; which is cheaper depends on local context, demand and costs.

PATH and CHAI (July 2021) advised researching local demand and understanding the operating requirements and costs of the equipment under consideration. A Global Fund briefing note on centralised and decentralised supply (August 2023) says cost effectiveness depends on local context and conditions.

What each option pays for

Cost item	On-site PSA plant	Delivered cylinders or liquid oxygen
Equipment	Plant, installation, housing or shelter, ventilation, air conditioning and heating, diesel generator, high-pressure cylinders and accessories (WHO, 2023)	Providers generally handle cylinder procurement, filling and maintenance under a lease, with a deposit before a monthly rental fee (PATH and CHAI, 2021)
The gas itself	Made from air with electricity: about 1.22 kWh per m³ of total flow, a rule of thumb in 2020 WHO COVID-19 interim guidance	Refill fees, with transport, inspection and maintenance often bundled into the refill cost (PATH and CHAI)
Logistics	No deliveries for the daily supply	Supplier networks set response times from hours to days and logistics costs (PATH and CHAI)
Losses	Part of the product gas is used to regenerate the sieve beds and is allowed for when sizing (HTM 02-01)	Liquid oxygen vaporises continuously, as much as about 5% a day depending on the tank (WHO, 2023)
Running costs	Spare parts, scheduled maintenance, repairs, electricity, diesel, distribution and staff salaries (Global Fund)	Contracts with a third party; accessories such as regulators are paid by the lessee (WHO; PATH and CHAI)
Planning horizon	WHO (2023): detailed financial planning for about 20 years; Global Fund: life cycle on average 10 years	WHO (2023): detailed financial planning for about 20 years

What the sources say about the balance

Assist International, answering on Open Critical Care, says liquid oxygen is generally more expensive than PSA because of the cost of equipment, supporting infrastructure and distribution, although after the initial investment in a very large-scale system the cost diminishes over time. The Global Fund note lists the elimination of transport costs as an advantage of plants at each facility, and substantial investment in trucks, garages, cylinders and storage as a drawback of central filling. NHS England guidance, HTM 02-01 (2026), says PSA systems should only be considered where geographical or environmental constraints prevent liquid oxygen or compressed-gas supply.

Pressure, purity and electricity

The ULTRAOX datasheet states that each extra bar of compressor pressure adds 7% to total electricity consumption. Purity also counts: a Global Fund note (April 2024) states that a plant specified for 95% ±1% needs larger equipment, with higher capital and power costs, than one specified for 93% ±3% for the same flow. WHO (2020) said to use the manufacturer's technical specification for a detailed power estimate.

Ultra Controlo states that ULTRAOX can cut oxygen costs by up to 70% over 10 years compared with cylinder or cryogenic supply. The ULTRAOX datasheet states that local production minimises the cost of handling and storing high-pressure cylinders and avoids rental, transport and evaporation costs, and notes that oxygen left in returned cylinders is paid for as if it had been consumed. ULTRAOX is designed for a minimum lifecycle of 150,000 hours.