Possible Clues:

• --- heater, off-peak electrical device
• Attic's purpose, often
• Silo's purpose
• Stowage
• Rate other gases differently, but they keep you warm
• Depository space for goods
• It's for the South to get furious at being kept in like this
• Charge for keeping silver in warehouse
• Where the shop keeps silver?
• Turns bad when kept there over time (7)