Smart Electric Meters are pretty accurate and are probably even more accurate than your old mechanical electric meter of years ago.
The smart electric meter has no mechanical moving parts which makes the smart electric meter pretty accurate when it comes to metering.
My electric bill has remained the same amount since I've had my smart electric meter installed by the electric utility so the smart electric meter must be just as accurate as my old electric meter was.
It is possible that an electric meter could be defective and cause a non accurate meter reading and then the new meter could be more accurate and your bill spikes but in most cases the new electric smart meter will be just as accurate as your old electric meter.
You should not see an increase in your electric bill just because a smart meter was installed and if you did see an increase you either used more electricity or something is wrong with the meter or something was wrong with the old meter.