When two providers quote different totals, the first question is whether they are offering the same equipment. Brand names alone do not settle it. Two units from the same maker can have different tank sizes, media volumes, or flow ratings, and two providers can quote the same brand with different models underneath.
Get the model number and the spec sheet for each quote
Ask every provider for the exact model number of the unit they propose, then find the manufacturer's spec sheet for that model. Read the rated capacity, the rated flow, the media or resin volume, and the listed operating pressure range. Write these numbers beside each quote. If a provider cannot give you a model number, treat the quote as incomplete.
Check what the rated capacity was tested against
Spec sheets state capacity under stated conditions, such as a particular water hardness or contaminant level and a particular flow. Ask each provider what water conditions they used to size the unit. If the conditions differ from your own water test results, the capacity figure does not describe your home. Ask them to explain the sizing in plain terms.
Match the replacement and service terms
Some quotes include the first replacement of media, filters, or cartridges and some do not. Ask how often the consumables must be replaced for the model they quoted, what each replacement costs, and whether the provider or the manufacturer supplies them. Compare these terms as carefully as the equipment itself, because they set the cost of ownership for years.
Check the provider, not just the price
Confirm that each provider holds the license or registration your local rules require for this kind of work, and ask whether they carry liability insurance. Ask for references from installs of the same model type. You can begin a shortlist in the provider directory, and if you want to understand how listed providers are reviewed before you rely on them, read our methodology page.
Make the final comparison on one sheet
Line up the model number, rated capacity, rated flow, consumable plan, warranty terms, and total price for each quote in the same columns. Any quote that cannot fill every column is the one to question first.