The purchase price is the number that gets the most attention, but it is only the first bill. A treatment system draws on consumables, salt, electricity, and sometimes water it discards on purpose. Over the life of the equipment, those running costs can outweigh the difference between two install quotes. This explainer shows what to price and how to put two providers on the same footing.
The main running costs
Most systems carry some combination of these recurring costs. Replacement cartridges or media are the most visible, and their interval depends on how much water your household uses and what the water contains. A softener uses salt on a schedule set by hardness and regeneration settings. Reverse osmosis units discard reject water during production. UV systems need replacement lamps and sleeves, and pumps or control heads draw electricity every day.
Ask for the replacement interval and its basis
A replacement interval is only useful if you know what it assumes. Ask whether it is measured in gallons used or in months, since a larger household reaches a gallon limit sooner than a smaller one. Ask whether the interval assumes a specific water test result, and if so, whether you need to supply a current test to keep the estimate accurate. An interval that quietly assumes soft or clean water will undercount your costs in a harder or dirtier supply.
Build a same-basis worksheet
Ask each provider to fill in the same worksheet so the totals can be compared. List each consumable part by name, its replacement interval, and its unit price. Add the expected monthly salt use for any softener, the reject ratio for any reverse osmosis unit, and the power rating for any pump or UV lamp. Include the cost of one routine service visit per year. Put the totals for five years side by side, and check that each provider used the same household size and water assumptions.
Watch for the costs that hide in the fine print
Some quotes omit the cost of a replacement that is not part of the standard schedule, such as a sediment pre-filter or a lamp housing. Others leave out the labor for a scheduled change. Ask directly whether any routine item is excluded from the quote and whether the provider charges a trip fee for each replacement visit. A low quote with a high consumable schedule is often the more expensive choice.
Use the total, not the sticker
Once you have the five-year figures, compare the totals and not the purchase prices. A higher install quote with lower consumable and salt costs can be the better buy. If a provider will not complete the worksheet, treat that as information too. You can start your comparison in the provider directory and then ask each shortlisted company for the same written figures.