What's the difference between modeling pre-tax versus post-tax?

When modeling post-tax we basically treat all project cash flows as either increases or decreases to income. For example, if the first-year energy savings is $20,000, and your customer has a federal tax rate of 30%, then that will result in a negative $6,000 ($20,000 * 30%) of cash flow resulting from tax consequences. When modeling pre-tax we don’t treat any cash flows as an increase or decrease in income. Note: the user specifies the ‘Tax Treatment’ for their proposal, in the 'General Information' section of the proposal editor.