So which is better, copper or stainless steel hot water cylinders? It’s the question we hear most often from installers. The honest answer is that there’s no one-size-fits-all winner, but each material brings distinct advantages depending on your project.
We’ve been manufacturing copper cylinders since 1977 and stainless steel since 2012, which means we’ve seen both materials perform across hundreds of installations. Below, we’ve broken down the key features and benefits to help you choose the right material for your application.
Copper
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.
Affordability
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.
Flexibility
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.
Recyclability
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.
| Solar Coil Tube Length | 6m |
| HP Coil Tube Length | 12m |
| Surface Area Solar | 1.62m² |
| Surface Area HP | 3.24m² |
| Volume Solar | 1.28L |
| Volume HP | 2.56L |
Stainless Tube Spec.
| Solar Coil Tube Length | 14.5m |
| HP Coil Tube Length | 29m |
| Surface Area Solar | 1.5m² |
| Surface Area HP | 3m² |
| Volume Solar | 5.3L |
| Volume HP | 10.6L |
Still not sure if stainless steel or copper is best for your system? Get in touch with us!