With the right chemicals, it's possible to build an absorption fridge, which requires only a small heat source and no electricity. Failing that, I'm sure you could do something creative with ice magic.
This does again raise the question of where the blood reagents are going to come from, if there are requirements for it to be human. Tish seems to be offering to quench the immediate need, but longer term? They may have to wait until someone is executed, I fear...
EDIT: Actually, does Leo even count as human, given his liony nature? If so, does he still have human blood while he's a cat?
Tish is closer to human than a scaler is, but it seems a bit premature to assume she'll do...
Like I mentioned on twitter, Leo is a human. Leo is sometimes a lion, but he is a human. Weres are some ridiculous magic, mainly because Gaea's fault.