The sentiment toward cryptocurrency mining in the provided passage appears to be negative. The passage mentions several concerns and challenges associated with cryptocurrency mining, including:

Growing electricity demand: The passage highlights the rapid growth in electricity demand associated with cryptocurrency mining, which can be seen as a concern for energy consumption.

Attention from policymakers and grid planners: Policymakers and grid planners are concerned about the impact of cryptocurrency mining on electricity costs, reliability, and emissions, indicating a negative sentiment.

Concerns about the energy-intensive nature: The passage mentions concerns about the energy-intensive nature of cryptocurrency mining and its effects on the U.S. electric power industry, including strains on the electricity grid, potential for higher electricity prices, and effects on carbon dioxide emissions.

Requests for mandatory disclosure: Members of Congress have expressed a desire for a "mandatory disclosure regime" regarding emissions and energy use by cryptocurrency miners, which suggests a negative view of the industry's transparency.

Challenges in estimating energy use: The passage discusses the difficulty in accurately estimating the electricity use of cryptocurrency miners, which can be seen as a challenge and a potential issue.

Overall, the passage portrays cryptocurrency mining in a negative light due to its perceived impact on electricity consumption, the environment, and the challenges associated with tracking and regulating it.