Use 'bank up' when talking about preparing for future needs or uncertainties.

Future Planning

'Bank up' is often used with money-related topics, suggesting accumulation of funds.

Financial Context

Can also refer to non-material things, like energy or time, being conserved.

Indicates the act of piling up materials like soil, sand, or snow.

Often used when the aim is to prevent something, like water or cold air, from getting in.

Suggests a proactive step taken to guard against natural elements.

Use 'bank up' to describe making something, often a fire or heat, stronger or more intense.

Implies maintaining heat over a period, especially in a fireplace or stove.

'Bank up' in this sense may be more common in informal conversation, not formal writing.