@Joy1101 That's a very generous refund for not having hot water for a total of about 15 hours, 8 of which they were presumably asleep.
In the future, it's best to offer what you feel is an appropriate refund for a non-working amenity early on, like when they report it and you start working on getting it fixed. "So sorry about that, we should be able to get it all working again by midday tomorrow and we'll be giving you a 50% refund for the first night for the inconvenience."
If you wait for them to ask for a refund, then you've kind of put the ball in their court, instead of acting confident and matter-of-fact about what you should do as a host in that situation.
And the ones who report a problem and in the same breath demand some refund are just scammers.
You don't have to worry that they might not have asked if you hadn't offered- guests who take things in stride without expecting to get money back for a minor inconvenience will say "Oh no, that's not necessary, we know things can go on the blink without warning, it was only a few hours, no big deal."
I've had guests who missed their first night due to overbooked flights, and since they had booked 10 days with me, even though it certainly wasn't my doing, I offered to reffund them that first night. In both cases the response was "Oh heavens no, it wasn't your fault".
But do try to avoid throwing refunds at guests for every minor inconvenience- it sets a bad precedent for guests thinking anything that isn't perfect deserves monetary compensation. Simple apologies and maybe a gift card for a local cafe can be appropriate and enough for many little glitches. Hotels certainly don't refund guests because something in their room isn't working properly- they just go in and fix it.
Nor does refunding guests, or running around trying to please fussy guests guarantee a good review, as many a host has found out.