What is the term for the sum of money set aside for items like electrical and plumbing fixtures whose actual costs are unknown?

The term that accurately describes the sum of money set aside for items like electrical and plumbing fixtures, for which actual costs are not precisely known, is "allowance." In construction and contracting contexts, an allowance is a specific amount of money included in a budget to cover the cost of particular items. This is often used when the exact price is uncertain at the time of budgeting, allowing flexibility to account for variations in costs later in the project.

In contrast, escrow refers to a financial arrangement where a third party holds funds until certain conditions are met, which doesn't apply here. Allocation typically refers to the distribution of resources or funds within a budget but does not specifically designate a sum for unknown costs of specific items. The option that combines both escrow and allowance would not fit, as they serve different purposes in financial terms. Therefore, allowance is the best term to use in this context.