What’s producing heat under bonnet overnight?

[dash]

Two defrosted circles on the bonnet suggest some heat beneath, but from where? As far as I’m aware there’s only the injectors anywhere close (and there are 3 of them!!).
Battery seems ok (monitored regularly using BM6), so not a significant energy drain.
Anyone else noticed this?

[APS]

As the outside temperature drops, the engine will take longer to cool down than the bonnet and is effectively giving off heat until it is the same as the ambient temperature.

[dash]

Not this time. Car has been unused for 2 days.

[APS]

Re-read my reply. This is just a question of thermal inertia. The same will apply to the ground underneath the car which will also contribute some heat that flows up thought the engine bay.

[Kental]

Are the frosted bits where the sound deadening is so blocking the ground effect

[APS]

1 minute ago, Kental said:

Are the frosted bits where the sound deadening is so blocking the ground effect

Exactly. There will be openings in the sound deadening for the wash nozzles and these areas will be kept warm by the engine and ground beneath while the frost forms.

[flash22]

2 minutes ago, APS said:

Exactly. There will be openings in the sound deadening for the wash nozzles and these areas will be kept warm by the engine and ground beneath while the frost forms.

the washer jets are in the scuttle tho

It is more likely RTF/paint contamination it just froze at different rates

or the local fox/cat has sat on the car when it was still warm

parked under a carport or tree may explain the 4 drop marks in a row