Water heater may be the culprit.

Fior a 30 day billing period that averages out to ~107 amps at 240 V continuously.

A meter mis-read could be the cause.

An electric water heater is normally protected by a 30 A 240 V breaker, so even if it was completely on the whole time it would barely be 28% of the power on the bill.

Are you sure there are not other new account charges on the bill?
Or it is for more than one month?

I have seen first new bills be high since they start charging on the day ownership changes, but the billing department lags enough the bill covers almost 60 days.

Also, if you are getting any kind of shock at the sink, you need to have an electrician check it out pronto. It could be related to the old water heater, but in any case, don't delay on this one.

"that averages out to ~107 amps at 240 V continuously"

Your math is flawed.

770Kwh in 30 days (30 X 24hrs=720hours) is an average draw of just over 1kw. A defective WH element could easily dissipate that, along with night lighting etc.

My house has half that much in parasitic loads.

Wayne, I agree with your math, but I want to come to your house to play. 500W of parasitic loads means you have lots of toys :-) With 8 computers sleeping, routers, clocks, inactive appliances and battery chargers, my house adds up to less than 100W.

Yes- I have lots of stuff, but parasitic load was perhaps not the phrase I should have used. Some things I could shut off, but choose not to, for instance a battery charger for the standby generator, and a couple of substantial UPS devices.

To me, there is no point in having a UPS if it isn't a "U"PS, so call it self imposed parasitic load.

One of the first things you should do is find out why that sink shocks its user, what was a little tingle yesterday could be a heart stopper the nest time someone uses it. Maybe the water heater as others suggested, or maybe a worn bare wire etc.

If the sink is shocking you, you have current going to ground. Check to make sure the disposal is not reverse phased. Turn off each circuit breaker one at a time while watching the meter. It should be obvious when you get the right circuit as the meter will slow down considerably. Once you isolate the circuit you should be able to determine the culprit

All the other suggestions are valid and definitely have the shocking sink checked. Something to consider also, was the first bill an actual read or was it estimated? I just bought a house myself and the first bill, for 12 days was $115 and had usage of about 1100 kwh.....it was estimated and when I checked the meter it was over estimated by 1015 kwh.....just something to consider.

"Your math is flawed."

Unit conversion error.

It is ~4.5 Amps at 240 V, but 8.9 A at 120 V.

Remember that while there is 240 V across the element, the voltage to ground is only 120 V.

Almost 9 amps to ground is a little high for a defective heating element.