Buying power is defined as the cash dollar amount available for trading in the account. For unrestricted cash accounts, all buy trades are debited and all sell trades are credited from the cash available to trade balance as soon as the trade executes, not when the trade settles.
For example, if the account has $10,000 settled funds, a deposit of $10,000 is received today, and the account has a $10,000 credit balance from unsettled activity, the account buying power would be $30,000.
For cash accounts restricted for good faith violations, the buying power will not include unsettled cash account sale proceeds.