A Data Warehouse is needed when:
Excel or Access cannot meet your reporting needs.
- Too much data for Excel or Access to handle
- The level of sophistication/complexity that you require for your reports is more complex that what you can do in Excel/Access
You are wasting too much time building reports.
A data warehouse can be something simple at a very low cost solution or one that runs the IRS. The point being how much time are you spending on developing the reports vs having it automated for you which is among the primary objectives of a Data Warehouse.
Number of data sources are many.
Do you have to pull data for your reports from one source or many? Do you have to copy data manually or can it be pulled in automatically for you. If you have pull data from a number of sources (each case is different) then a Data Warehouse makes sense. Imagine you pay for an employee to copy and paste data from one report to another all day long? A Data Warehouse automates it.
Assurance of Reports is critical.
A final point to consider when looking at creating data warehouse. If your employee (s) leaves the company are you able to assure that the reports being created manually will work? If you need the reports regardless of the cost, then a data warehouse is the way to go.