The right home is the one that’s right for you. Don’t let anyone tell you otherwise.
Your best bet to keeping your home heated during the winter months is to set your comfort level temperature and leave it at that.
While it’s unlikely this trade-off is a perfect 1:1, the real question you need to ask is: are we upgrading, or downsizing? One of those will impact your negotiation options, while the other may cost you even more as a result of timing.