Which statement is true regarding electric boilers?

Electric boilers do not require a chimney because they do not produce combustion gases as traditional fuel-fired boilers do. Instead, electric boilers generate heat through electrical resistance, converting electrical energy directly into thermal energy without the need for combustion. Since no fuel is burned, no flue gases are released, allowing for the absence of a chimney or flue system. This design feature not only simplifies installation but also makes electric boilers an environmentally friendly option, as they typically have lower emissions compared to their combustion counterparts.

In contrast, other options misrepresent certain features or operational characteristics of electric boilers. While electric boilers can be designed for low pressure, they aren't limited to only that type. Although gauge glasses are not always required for electric boilers, particularly those designed with safety interlocks and controls that display water levels electronically, some installations might still use them. Lastly, the economic operation of electric boilers can vary significantly based on local electricity rates and usage patterns, so they may not universally be considered economical to operate.