Method and boundaries
Annualized reserve for each separately charged item = final replacement cost × 12 ÷ repeat interval in months. Scheduled spend counts replacements due from month 0 through month 11, then adds one entered annual-plan fee and your extra visit count × final visit price. A change due exactly at month 12 belongs to the following period.
Example arithmetic, not Dubai market prices: a cartridge set costing AED 150 every six months, next due in three months, needs two changes in this window: AED 300. Two separate visits at AED 80 add AED 160, giving AED 460. A membrane costing AED 600 every 24 months, next due in 18 months, adds AED 300 to the annualized reserve but nothing to this period’s scheduled spend.
Avoid counting included work twice
Mark a component covered by the annual plan only if every required change within the budget period is covered. Partial coverage of an item’s replacement events is not supported: if a plan pays for only some changes, request a separate itemized budget instead of changing the true maintenance interval to make the result fit. Do not add a visit already included in a cartridge replacement or service plan. This tool assumes one uniform extra-visit rate and one annual plan fee payable in the period; it does not prorate a mid-term contract or subtract past payments.
Assumptions and input limits
All amounts are final AED prices including any VAT and delivery; tax is never added automatically. Amounts allow two decimal places and are capped at AED 1,000,000 per input. Up to eight component rows, intervals/next due dates of up to 120 whole months, and up to 24 extra visits are supported. These limits catch entry errors and are not maintenance recommendations. Annualized lines are rounded to two decimal places before summation. Blank inputs and unresolved scope prevent a complete budget.
Replacement may be governed by time, usage, capacity or condition under the manufacturer’s instructions. The calculator does not prescribe an interval or verify water safety. Repairs, unexpected failures, future price changes and whole-system replacement are not included.
Read the cartridge replacement and maintenance guide · Water filter maintenance services