You are incorrect. The post above this is very helpful in explaining.
The non-refundable language doesn't mean you won't get a bigger check in April. I told you, I got a $12,000 check for my 2018 taxes.
Non-refundable means this:
If your Total Tax liability was only $5,000 for the year, then you can only use $5,000 of the credit and the remaining $2,500 is lost. The lost $2,500 is the non-refundable part. If the credit was "refundable" then any unused portion would also be paid to you.
If your Total Tax liability was $10,000 for the year, then you can use $7,500 of the credit, to offset it.
Total Tax is not what you necessarily what you owe in April. Most US tax payers either pay taxes on every paycheck (W2), they pay quarterly taxes or they pay it all in April. In April, if your Total Tax is $7,500 or more, you will get to use all of it. If you overpaid taxes during the year, then you will get a a refund. The credit is additional money in your refund check. If you happen to owe money, the credit will reduce that amount.
Look at your last year 1040 Line 24. Is that number bigger than $7,500?
Stop looking at line 34/35a (Refund), or 37 (Owed) it is unrelated to those.