How can thermal efficiency impact operational costs?

The correct choice underscores a critical relationship between thermal efficiency and operational costs, particularly concerning fuel consumption. When thermal efficiency is lower, it indicates that the boiler is not converting the energy from fuel into useful work as effectively as it could. This inefficiency means that more fuel must be burned to produce the same amount of steam or heat output, directly increasing fuel costs.

In practical terms, for a boiler operating under lower thermal efficiency, the additional fuel consumption results in escalating expenses, which significantly impact the overall cost of operation. Consequently, maintaining or improving thermal efficiency is vital for reducing fuel costs and enhancing economic performance in boiler operations.

The other options do not accurately represent the relationship between thermal efficiency and operational costs, as they either misunderstand the implications of efficiency on consumption and costs or assert that efficiency has no effect at all, which contradicts fundamental principles of energy management.