It should be worth about €1,890 to you.
It has nothing to do with tax credits in your case, as you'll use up all of your own credits if you earn €23k.
The benefit is the standard rate cut off point; you are each entitled to earn €32,800 before you hit the 41% rate of income tax.
Married people can transfer up to €9k of this €32,800 between them.
So, since you only need €23k of your band, you can transfer most of the remaining €9,800 to your husband.
He will then pay tax at 20% instead of 41% on an additional €9k of his income - end result is his take home pay increases by 21% of €9k, which is €1,890.