The most common and most likely answer to this crossword clue is the 11 letter word INSULATIONS
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Buddy explains!
The straight part
We know that "They’ll save on heating bills" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case they’ll save on heating bills = insulations.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does INSULATIONS mean?
INSULATIONS noun- The act of insulating; detachment from other objects; isolation.
- The state of being insulated; detachment from other objects; isolation.
- Any of a variety of materials designed to reduce the flow of heat, either from or into a building.
- The act of separating a body from others by nonconductors, so as to prevent the transfer of electricity, heat, or sound
- The state of a body so separated.
- A medium in which it is possible to maintain an electrical field with little supply of energy from additional sources.