Don't forget that our air is somewhat drier than most places (in Alberta we call 15% humidity "rain") so although I agree 25g seems like a lot of evap it's not completely implausible. I go through about 5g per day on my 75g right now, about 5g every two days over my 72g, and about 5g per week over my 20g. This is ... I would estimate about 2, 3 times as fast now, as compared to the winter months.
What does concern me a little is that 25g every couple of days is a lot of water being added to the ambient air. Teevee, it's a good thing you have a ceiling fan, that way you can keep the air moving and prevent mildew from taking hold...
(But then, I suppose with that greenhouse attached to your house, you probably already know a thing or two about controlling excessive humidity.
)