The 2025 Review of ASIC Miners: New Models vs. Older Ones with Immersion Cooling.

Many operators running the previous generation or older ASICs in 2025 are concerned if these machines can remain relevant in the present state of the mining industry, which is very different from the situation in 2021, when Bitcoin price was at the peak of the bull market. 

Back then, it seemed that mining would yield rewards even with not the most efficient ASICs. Now, mining devices of older generations that run on factory settings won’t be able to compete with new flagship models - that is a hard fact, a reality of 2025. 

Nevertheless, it does not mean that these miners should be salvaged to be used as spare parts or e-waste recycled, let alone go to a scrapyard. Give them good firmware and a better cooling system, and some older ASICs could give new ones a run for their satoshis. 

The following blog post analyzes the modern mining environment and offers a review of 2025 ASICs in comparison to older models that feature an immersion cooling system. By its end, you will find out whether the previous generation still has what it takes to earn Bitcoin.         

The mining industry in 2025: Keeping up with the highest efficiency standard 

Now, efficiency is the name of the Bitcoin mining game. The Bitcoin mining difficulty is at the highest ever recorded, and average global electricity prices are not showing a tendency to decrease, given the growing demand coming from data centers, AI projects, and the EV industry. 

Despite Bitcoin briefly reaching the once highly anticipated $100,000 threshold, it did not translate to easier earnings for Bitcoin miners as the network difficulty outpaced the price movement.  

The consequence of network difficulty outpacing price in 2025 is that inefficient mining operations are at a disadvantage. Presently, yield-making BTC mining depends directly on energy efficiency, a factor often expressed as Joules per Terahash (J/TH). This metric measures the electricity consumed per unit of computing power.

Therefore, minimizing power consumption is now a key thing for ensuring operational sustainability in Bitcoin mining. With network difficulty at record highs and electricity prices remaining stable or increasing, the cost of energy per terahash is the most significant operational expense. It means that optimizing J/TH is super important for maintaining profitability and remaining competitive in 2025 and in the short-term future.

The latest generation of Bitcoin mining ASICs are now creating a new standard for energy efficiency. Models such as the Antminer S21, Antminer T21, and Whatsminer M6X series are capable of hitting the efficiency levels in the range of 17 to 20 Joules per Terahash. Such a low J/TH figure is basically the benchmark against which older mining hardware must compete to stay relevant.

The challenges older generations of ASIC miners are facing at the moment 

The high efficiency standard set by the latest ASICs indeed pose a problem for older mining hardware. To showcase this problem, we are going to review a widely used model like the Antminer S19 Pro.

The Antminer S19 Pro, a very popular ASIC, is a good example of performance on stock settings with air cooling. This model operates at a hashrate of around 110 Terahashes per second (TH/s). Its power consumption under these standard conditions is approximately 3250 Watts. This results in a stock energy efficiency of about 29.5 Joules per Terahash (J/TH).

Air cooling, the method used in many older ASIC models, including Antminer S19 Pro, becomes problematic when managing the heat coming from powerful processing chips, sometimes resulting in heat buildup. When temperatures rise too high, thermal throttling kicks in, a mechanism that reduces performance to prevent hardware damage. Prolonged exposure to high temperatures is also harmful for internal components, shortening the ASIC’s lifespan. 

Apart from the problems of heat management, air cooling has several other drawbacks for mining farms:

• High noise levels from powerful fans required for air cooling.

•  An airflow through the miners pulls in particles and moisture, resulting in buildup, corrosion, reduced performance, and possibly even hardware failures.

• Air-cooled setups require facility-level cooling systems and regular maintenance.

You would be right to point out that these issues are also true for the latest generation of air-cooled ASICs, such as Antminer S21, Antminer T21, and Whatsminer M6X series. However, the higher energy efficiency of these newer models is a big advantage that balances out these drawbacks, allowing the latest ASICs to maintain overall cost-effectiveness and profitability. Miners who rely on older machines find it harder to cope with additional costs. 

The challenge for older hardware becomes even clearer when comparing performance metrics directly. The table below illustrates the difference between a standard Antminer S19 Pro on air cooling and a new generation Antminer S21.

The efficiency gap and higher operational costs clearly demonstrate the challenge older ASICs face in today's BTC mining realities. But there are options for improvement, such as advanced cooling methods that can squeeze out extra capabilities from existing hardware.

Immersion cooling could keep older ASICs in the game 

The immersion cooling technique means submerging mining hardware directly in a dielectric fluid that does not conduct electricity. It absorbs and transfers heat away from the ASIC chips and components and greatly improves the energy efficiency of the mining hardware that translates to lower J/TH figures. 

This method also reduces or completely mutes the loud noise produced by air-cooled miners by eliminating the need for high-RPM stock fans. The heat is instead transferred from the fluid to external cooling systems, which are usually placed outside the mining area. 

Immersion cooling protects ASIC components against dust and humidity by fully covering the hardware in a non-conductive dielectric fluid, thus preventing the accumulation of dust and lowering the risk of corrosion. This protective barrier reduces the need for frequent cleaning and maintenance.

It also allows reusing the heat generated by mining hardware in other applications by capturing and concentrating it in the dielectric fluid. From then on, the heat can be directed to facility spaces, greenhouses, or used in different industrial processes. 

Optimized firmware for better performance of older ASIC miners 

Firmware is the software that directly controls ASIC components. Factory firmware is pre-installed with default settings, whereas custom or optimized firmware is a piece of software designed to control and modify operational parameters. It functions as a layer of software control, allowing operators to tweak the ASIC's parameters in specific ways. These parameters include the voltage supplied to the chips and their operating frequency. By modifying these settings, operators can directly influence the miner's hash rate output and its power consumption. 

Optimized firmware, when combined with immersion cooling, takes ASIC performance beyond standard settings. It allows for overclocking, which can increase hash rate, sometimes by 30% or more. Through algorithm optimization, custom firmware allows for automatic frequency tuning and profile generation.

Apart from managing performance, ASIC firmware allows real-time monitoring of individual chip performance and temperatures through management systems like BiXBiT AMS. Firmware also contributes to improved stability and error handling, providing notifications for critical events, such as hashrate drops, high temperatures, or unauthorized pool changes. 

The firmware also provides safety features: it can automatically halt mining if critical temperatures are reached on specific units. This helps protect the hardware and maintain stable operation. Quality firmware also has security feats like embedded antivirus, 2FA authentication, and SSH access control.

How non-optimized and optimized ASICs compare against the latest model 

We can now analyze how combining advanced cooling and custom firmware improves the operational profile of an older ASIC like the Antminer S19 Pro. The firmware provides the control to adjust hardware parameters safely, while the cooling ensures temperatures remain low and stable so that the hardware can handle increased power loads.

The table below provides an approximate comparison of key technical and operational aspects between an Antminer S19 Pro on stock air cooling, the same model optimized with advanced cooling and custom firmware, and a current generation Antminer S21 on stock settings. 

The obvious results of optimization are seen in increased hash rate and improved energy efficiency. Optimized firmware allows the ASIC to operate at higher frequencies and voltages than factory settings permit, creating means for overclocking. 

For an Antminer S19 Pro, this can mean a significant increase in hash rate from its stock ~110 TH/s to an achievable ~155 TH/s through optimization. While power consumption increases to approximately 3400 Watts at this higher output, the better thermal management from advanced cooling, combined with precise firmware control, results in improved energy efficiency. The operational efficiency (J/TH) can be reduced from the stock ~29.5 J/TH to approximately 25.2 J/TH.

Beyond performance numbers, the optimized setup can increase uptime thanks to better stability and the reduction of thermal problems that can cause shutdowns or errors in air-cooled systems. Furthermore, by maintaining lower, more stable temperatures and protecting ASIC’s components, advanced cooling translates to lower long-term maintenance needs and londer estimated lifespan of the older mining hardware compared to new models like Antminer S21 with air cooling and stock settings.  

Conclusion: Don’t give up on older ASICs 

The current state of the Bitcoin mining space, characterized by high difficulty and the efficiency standard set by the latest hardware, indeed poses some challenges for older generation ASICs. But it does not mean the equipment of the previous generation would soon become obsolete.

We have showcased that advanced cooling solutions, particularly immersion, and optimized custom firmware can keep older miners competitive by boosting performance, improving operational efficiency, and enhancing reliability. For Bitcoin miners who want to get the most value from their current hardware, incorporating these advanced solutions can help them maintain a competitive mining operation.

 FAQ

Is it worth buying older ASICs like Antminer S17 in 2025? 

Buying and running older ASICs like the Antminer S17 in 2025 will be challenging due to their low energy efficiency compared to current hardware. Their potential worth depends heavily on implementing advanced cooling and optimized firmware, along with very low electricity costs.

How does immersion cooling improve mining profits?

Immersion cooling improves the performance of mining by reducing operational temperatures and promoting higher hash rates. It also lowers operational expenses through decreased maintenance needs, extended hardware lifespan, and heat reuse.

Which Bitcoin miner has the fastest payback?

While newer, efficient models have lower running expenses per terahash, older models have a much lower purchase price, which determines how quickly the investment is returned under different operational conditions.

What is the best electricity rate for profitable mining?

Taking into account the average global electricity rates and Bitcoin mining difficulty, an electricity rate of $0.03 per kilowatt-hour or less is considered necessary for optimal cost-effectiveness.