Copper vs Stainless Steel – Which is Better?

An often asked question is which material is better suited for manufacturing hot water cylinders; copper or stainless steel.

We have been manufacturing Copper Cylinders since 1977 and Stainless Steel Cylinders since 2012 and although there is no definitive answer, each material has its own unique advantages.

We have compiled a list of the features and benefits below to allow you to make an informed decision on which material is best suited for your application.


Stainless Steel

Antibacterial Properties

Copper has been renowned for its excellent antibacterial and antimicrobial properties for centuries; copper will eradicate E-Coli, MRSA, Avian Flu, Legionella and 99% of bacteria within just 5 hours of contact.

Although Stainless Steel is still perfectly safe for use, tests have concluded that bacteria takes longer to deteriorate on a stainless steel surface than a copper one.

Heat Conductivity

Copper is one of the most efficient conductors of heat. It has a thermal conductivity of 401W/mK.

Thermal efficiency is vital for the efficiency of lower temperature, renewable heat sources such as Solar Thermal Panels and Heat Pumps.

Stainless steel has a much lower thermal conductivity than copper at just 14w/mK; this means that there is less heat transferred, but we compensate for this by specifying appropriately-larger coils.


Due to recent surges in copper prices, cylinders made from this material can be restrictively more expensive than their stainless steel alternatives.

This is particularly true for high-pressure/unvented cylinders which require thicker copper for their construction.

From a cost point of view, we would now suggest that copper should only be considered for higher-pressure units, if using a stainless steel version is impossible.

Although stainless steel cylinders have an initially lower upfront cost, the slight reduction coil conductivity could make them slightly more costly to run.

However, when you also consider that slightly less heat will conduct through their walls, everything probably balances out quite equally.


As copper is a very flexible material, it allows for a wide range of customisation options. Generally speaking, if a bespoke specification isn’t possible in stainless steel, it’s probably possible in copper.

We are one of the few companies in the UK able to manufacture bespoke stainless cylinders.

As such, we are usually able to accommodate any requirements our customers have, but stainless steel can be slightly more difficult to work with.


Copper is valuable as scrap as it’s an elemental metal. This makes recycling copper easy and cost-effective.

As stainless steel is an alloy, it requires separating into its key elements before it can be recycled, this is a more difficult and costly process.

Ability To Withstand High Pressure

Copper is suitable for use as a manufacturing material for unvented or pressurised units, but only if the thickness is adequately increased.

Stainless steel is a much stronger material than copper, so even the thinnest grades that we stock can be used for high pressure units.

Life Expectancy

Both copper and stainless steel are very resistant to corrosion when holding pH neutral water.

Private water sources however, tend not to be neutral, so cylinders in either material can corrode prematurely.

Copper Tube Spec.
Finned Copper Tube
Solar Coil Tube Length6m
HP Coil Tube Length12m
Surface Area Solar1.62m²
Surface Area HP3.24m²
Volume Solar1.28L
Volume HP2.56L
Stainless Tube Spec.
Convoluted Stainless Tube
Solar Coil Tube Length14.5m
HP Coil Tube Length29m
Surface Area Solar1.5m²
Surface Area HP3m²
Volume Solar5.3L
Volume HP10.6L

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