installment rate vs rate of payment

installment rate and rate of payment both are nouns.

Word	Noun	Adjective	Verb	Adverb
installment rate	Yes	No	No	No
rate of payment	Yes	No	No	No

As nouns, installment rate and rate of payment are synonyms defined as:

installment rate and rate of payment: the amount of money paid out per unit time

Other synonyms of installment rate include payment rate, repayment rate.

installment rate (noun)	rate of payment (noun)
the amount of money paid out per unit time	the amount of money paid out per unit time