The Umbrel Home is basically a $400 NUC whose power draw should idle around 10-12 watts, with activity around 30-40 watt or so.
The Dell Optiplex power supply can accomodate up to 180 watt draw if ever needed. Id speculate itd idle a little higher around 14 watts and actively be pushing around 65-70. Where im at that translates to an operational cost difference of about $40/year. So in theory, if this node remains in service longer than 5 years it may be cheaper to have gotten a NUC.
Umbrel on raspberry *
Look at bill and consumtions: 
where are you getting 100w?
Thats the power supply. Its limit is 180w. It doesnt draw that much on the regular.
Yes minimum is 90w without load but I put 100w because I think the server have programs running in background . Raspberry usually have less than 10w but I choose 15w because same programs need a lot o power from raspberry. Is just an estimation, not real but I want to show you that solution with optiplex is not good solution for server if you don’t have cheap energy or free.
In 2 years you pay another optiplex ( by bill of power consumtion)
Long term is ok to have raspberry.
If you have free energy from solar pannels is ok to have what that optiplex
