It depends on the heated area, the system you choose and how much of the building you heat at once. The figure that matters is peak demand: the load when everything you intend to run is running together.
Work it out before you commit to a system. Add up the rated output of the heaters for the zones you will use at the same time, then compare that against the capacity of your incoming supply. Your electrician or the manufacturer can do this from a plan of the building and a note of which areas need heat.
Zoning changes the answer. A church that heats only the nave for a Sunday service needs far less capacity than one heating nave, aisles and hall together, so a zoned design can bring a scheme inside an existing supply that would otherwise fail.
Where the supply falls short, an upgrade is one route and battery storage is another. Whether your existing wiring can carry the load is a separate question worth asking at the same time.