11 min readOn September 15, 2022, Ethereum’s transition to proof-of-stake (PoS) ended its reliance on general-purpose graphics (GPU) based proof-of-work (PoW) mining, a model Ethereum had employed since the network went live on July 30, 2015.
Bitcoin may still command the bulk of PoW, but when Ethereum’s GPU farms fell silent, they scattered across niche chains and hybrid compute hubs. The below analysis follows that journey, spotlighting 2025’s leading PoW networks, mining economics, new hotspots and why cost-driven security keeps PoW battle-tested.
Aftermath of the Ethereum merge
Proof-of-Work vs. Proof-of-Stake
PoW requires miners to solve cryptographic puzzles by performing repeated hash computations. This process secures the Bitcoin network’s integrity by making block creation computationally costly. PoS replaces computational effort with financial stake where validators lock up native tokens as collateral and are randomly selected to produce blocks, reducing energy consumption.
GPU exodus
Ethereum’s PoW network reached a peak hash rate of roughly 1.24 PH/s (petahashes per second) in mid-June 2022 . When the Merge retired GPU mining on September 15, over 1.2 PH/s of that capacity went offline.
In the following weeks, GPU hashpower shifted decisively to four leading PoW chains:
Ethereum Classic: Climbed from 26 TH/s to 236 TH/s, an 808 % increase.
Ravencoin: Rose from 2.76 TH/s to 16.88 TH/s, a 511 % increase.
Ergo: Jumped from 14.46 TH/s to 99.59 TH/s, a 589 % increase.
Flux: Grew from 1.34 MH/s to 9 MH/s, a 571 % increase.
Freed GPUs couldn’t switch to Bitcoin because BTC’s SHA-256 PoW relies on ASIC chips, making GPU mining unprofitable. Instead, miners migrated to four GPU-friendly algorithms:
Ethash (Ethereum Classic): Memory-intensive mining designed to prevent specialized ASICs and keep GPU rigs profitable.
KAWPOW (Ravencoin): Regularly changing calculations ensure GPUs remain competitive and resist specialized mining equipment.
Autolykos v2 (Ergo): Structured for simple GPU operations, making mining accessible without specialized hardware.
ZelHash (Flux): Tailored specifically for GPU mining, optimizing energy efficiency and profitability.
PoW chain survivors
Kaspa (KAS)
Kaspa positions itself as an alternative to networks like Bitcoin, branding itself as a form of "digital silver" to Bitcoin’s digital gold. The name "Kaspa" derives from the ancient Aramaic word for "silver" or “money,” underscoring the complementary relationship.
Technically, Kaspa is built on the GHOSTDAG protocol. This structure supports fast transaction speeds and produces one block per second, with ambitions to scale further, potentially up to 10 or even 100 blocks per second.
Monero (XMR)
Launched in 2014, Monero emphasizes user privacy and fungibility, ensuring transactions remain anonymous through technologies like ring signatures and stealth addresses. Monero utilizes RandomX , a PoW algorithm developed by Monero contributors and integrated since release 0.15. Ultimately, Monero enables fast, affordable transactions that remain free from interference or censorship.
Ravencoin (RVN)
Ravencoin launched January 3, 2018 as an open-source Bitcoin fork tailored for peer-to-peer asset transfers. Key parameters include a 21 billion coin supply, one-minute block intervals and an issuance schedule starting at 5,000 RVN per block. Mining algorithm KAWPOW uses GPU memory and compute cycles to deter ASIC centralization.
Ergo (ERG)
Ergo launched in July 2019 uses Autolykos algorithm, designed for GPU mining. Alongside this, Ergo enables advanced smart contracts and privacy tools, positioning it as a flexible foundation for decentralized applications.
Flux (FLUX)
Flux is a mineable PoW cryptocurrency that powers a decentralized cloud infrastructure designed for Web3. Flux supports a wide range of use cases, including paying for resources, collateralizing FluxNodes, and facilitating transactions on FluxOS. With over 13,500 nodes and vast computing capacity, Flux operates one of the largest decentralized networks globally.
Contemporary mining economics
Mining profitability hinges on multiple factors including token price, network difficulty, and electricity costs. While ASIC-based Bitcoin mining can remain viable at industrial scale due to energy efficiency and access to preferential power rates, GPU mining is more sensitive to fluctuations in token value and energy pricing.
Following Ethereum’s shift away from PoW, demand for GPUs fell sharply, prompting a wave of hardware decommissioning and consolidation. Today, most miners rely on pools to reduce income variability, as solo mining on smaller PoW chains carries high risk and often yields delayed or inconsistent returns.
Geographic shifts & regulatory climate
As Bitcoin’s hashrate continues climbing, global mining operations have strategically relocated to regions offering favorable energy conditions and regulatory clarity. Paraguay, for example, has emerged as a South American mining hub thanks to ultra-low hydroelectric rates from the Itaipu Dam, hosting up to 1.45% of global hashrate in mid-2025.
Similarly, Kazakhstan saw an increase in miners after China’s 2021 ban, drawn by deregulated energy and large-scale warehouse space. In Africa, countries like Ethiopia, Kenya, and Nigeria are leveraging local renewables in the form of hydropower, mini-grids, and solar, to power mining clusters and community infrastructure alike, signaling a broader trend of decentralizing hashpower into emerging markets.
How altcoin miners navigate energy politics and global regulation
Beyond Bitcoin, GPU-based altcoin miners are also adapting to energy politics and compliance demands. With regulatory pressures intensifying in the U.S. and Europe, many operations are relocating to regions with lighter oversight or surplus energy.
GPU-based miners are adapting to regional energy landscapes, with some turning to solar partnerships or low-cost rural power sources to remain viable. In Paraguay, GPU farms are teaming up with solar grid operators, while in the Middle East, miners are repurposing flared gas for efficient energy use. These adaptations reflect a broader trend where policy, energy economics, and decentralized infrastructure are becoming tightly interwoven.
Dual-use computing models
As mining margins tighten, operators are repurposing infrastructure for dual-use applications. One example is Hive Digital Technologies, which uses its GPU arrays for machine learning tasks during crypto market downturns. These GPUs switch back to PoW mining when token prices rise, offering a flexible model that balances blockchain validation with AI compute contracts. This approach improves capital efficiency and reduces reliance on volatile mining revenues.
Meanwhile, TerraVerde Energy is integrating Bitcoin mining with solar infrastructure through real-time optimization software. By dynamically shifting surplus solar power between the grid, battery storage, and mining hardware, this model ensures profitability by minimizing energy waste.
PoW’s enduring security model
Despite environmental scrutiny, PoW remains the most battle-tested mechanism for decentralized consensus. Here's why PoW is still the gold standard for trustless validation:
Externally verifiable work: PoW requires real, measurable computation making fraud and manipulation close to impossible.
Censorship resistance by design: To interfere with block production, an attacker must expend massive energy and capital, making censorship economically unviable under PoW.
Permissionless participation: Anyone with access to standard hardware can mine, reducing the risk of centralization and gatekeeping.
Proven resilience at scale: Bitcoin’s hashrate, exceeding 0.8 Billion TH/s, serves as real-time proof of PoW’s unmatched security and the scale of global miner participation.
Conclusion
PoW remains the most battle-tested and censorship-resistant consensus mechanism in crypto. From solar-powered rigs to AI-integrated clusters, alternative miners are innovating within the mining space out of necessity, to reduce cost.
The Ethereum Merge forced GPU miners to adapt, sparking new dynamics across niche PoW networks and hybrid compute models. While Bitcoin’s ASIC mining dominates in scale and security, smaller chains like Kaspa, Monero, and Ravencoin have become hubs for experimentation and community-driven resilience. Alternative mining isn’t competing with Bitcoin but adapting and focusing on flexibility and local utility.
