If you already are cooking on an electric stove (resistance coils or IR) you already have the higher voltage/amperage circuit - and induction is a definite 'step up' - so it's a no-brainer. For those of us who have gas, in the US/CAN, that's most probably on a 115VAC 30 (or even 15 or 20) amp circuit. Very much *not* enough to run an induction stove. For those in other countries, you already have high enough voltage but the conductors in the wires might not be thick enough to run the needed amperage (power is volts times amps) - but you quite possibly do. In the US, max allowable load on a circuit is 80% of its rating. In the US or not, the simplest thing might be to make sure you have a stove hood that takes exhaust out of the building - and be sure to use it. I've lived in Normandy so I'm quite aware that putting a vent through that kind of construction is a major deal. Ditto log construction (Maine North woods).
Also, if you're deciding on which induction stove / cooktop, if you need 'burners' that can match your gas stove, you need relatively large diameter magnetic coils. Many of the lower priced units are IMO undersized. Tri-layer cookware can somewhat make up for that (conducting heat from the inner area to the rest of the pan) but cast iron is a poor heat conductor. On top of that, heating just the center makes it stupidly easy to warp a pan - and pans need to sit flat to work on induction. Also get used to using a spatula rather than just picking the pan up to flip things with wrist action. Some induction units shut off when you lift the pan and stay off. The others just stop while the pan is up.
As usual, just my $0.02