These screw-ups happen when ConEd charges you based on an estimate of your power consumption -- not an actual meter reading.
Estimated bills are not uncommon, according to ConEd spokesman Allan Drury. They can happen for a number of reasons, typically when the power company can’t gain access to your building to check out the actual meter -- or, like in 2012, when utility workers went on strike and no one was around to do a real reading.
According to Drury, these estimates are based mainly on your prior usage, which obviously can vary based on any number of factors, like changing seasons.
If it seems unfair to charge customers based on little more than an educated guess, well, ConEd agrees. Sort of. On its website, the utility company offers some guidance on how to avoid estimated bills -- it even allows you to submit your own meter readings over the phone or online so you don’t get overcharged.