Why do stable compounds have a lower heat of combustion?

My brain somehow doesn't accept that more stable compounds require have less enthalpy. Isn't it like, if a compound is stable, it requires more energy to break the bonds because the compound doesn't want to react. However does have a less stable compound more energy so it doesn't require so much energy to break the bonds?




To answer the additional comment:


Heat of combustion is related to energy released by forming bonds of products and energy spent by breaking bond of reagents. 


Cyclopropane has more of stress on its bonds, that are therefore weaker and less energy was released by their forming. 


By burning, less energy must be spent to break them, while energy released by forming products is the same ( per CH2 ). Therefore the specific heat of combustion in MJ/kg is bigger.




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Chemical stability and stored chemical energy are 2 independent parameters.


Stability relates to energy needed to release the stored energy.


Typical fossil fuel like coal has energy typically about $\pu{40 MJ/kg}$. Explosives like TNT have typical energy $\pu{4 MJ/kg}$, so about 1 tenth.




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It has a direct mechanical analogy:


Stored potential energy is related to how deep can the centre of object mass fall.


Stability is related to energy needed to make the object to fall.


If you stood on 1 foot on an edge of a small stone, you would have relatively low potential energy, but low stability. All, what is needed, is a light touch.


If you stood on both feet on a floor of tourist watch tower, you would have relatively high potential energy, but also high stability. To make you fall, the tower would have to be destroyed or you would have to be thrown over the fence or through a window.


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