15 VAC transformers (mostly using a 115-120VAC primary, since you're in the USA)

https://www.ebay.com/sch/i.html?_from=R40&_sacat=0&_nkw=15VAC+transformer&_sop=15
Electric-T, you seem to have multiplied your primary (input) voltage times your secondary (output) voltage, but I can't imagine why. The product gives no meaningful measure.

V×I=P, yes that's correct, and 120×15=1800 is correct but it's just arithmetic without units to make it meaningful. If you meant 120

**A **x 15

**V**=1800

**W**, then it's a meaningful equation but it begs the question of where you got the 120 Amps current draw you're using in the calculation. An application with that kind of current draw would usually use the 120V without stepping it down; or better yet, use a 240V outlet and less current.

But I suspect you're not using 120 A in your project and you're still unclear about how to calculate current? If that's the case, then say so and it'll help us to advise you.

For future reference, any time you're doing algebraic calculation, use the units of measure. It stops a lot of nonsense equations.