The main heat sources in the core are secular cooling (i.e. losing primordial heat), latent heat due to the ongoing solidification of the inner region, compositional energy (essentially gravitational energy, the lighter elements in the core do not solidify and some fraction of the core solidify these elements rise up to the liquid part) and radioactive decay.

The estimates in Earth's Core (by Cormier et al., nice book) are around 0.3 TW for radioactive decay and a few TW (2 to 6) each for the others.

As an order of magnitude estimation, compositional changes, phase transition and original heat loss contributes equally, while radiogenic heat is only a minor contribution.

The heat balance we measure at the surface has obviously much more than this. We have to take into account the secular cooling of the mantle itself (16 TW), plus the heat production of continents (8TW) and again the mantle (11 TW), which are mainly radiogenic (data here from the Encyclopedia of Solid Earth Geophysics).
Note that every estimate, despite being in line with scientific consensus, is subject to high uncertainties, due to the very difficult nature of these kind of measures/models.

To close going slightly OT, this combination of heat production and heat loss is the driving force of hot spots and plate tectonics. Which means that the cooling dynamics of the earth is responsible for essentially the entirity of what we observe in the solid earth. Earthquakes, volcanic eruptions, tectonic movement, but also interactions with surface geomorphology are all byproducts of a ball of molten rock cooling.