At saved game load:

Exception processing alert Power_Alerts.Alerts.Alert_GeneratorFuelLow: System.NullReferenceException: Object reference not set to an instance of an object
at Power_Alerts.Alerts.Alert_GeneratorFuelLow.<GetLowFuelGenerators>b__0_4 (RimWorld.CompPowerTrader pc) [0x00028] in <be3a0ec0cc2e421eb4567318efa8ad51>:0
at System.Linq.Enumerable+WhereListIterator`1[TSource].MoveNext () [0x00037] in <351e49e2a5bf4fd6beabb458ce2255f3>:0
at System.Linq.Enumerable+SelectManySingleSelectorIterator`2[TSource,TResult].MoveNext () [0x0006f] in <351e49e2a5bf4fd6beabb458ce2255f3>:0
at System.Linq.Enumerable+SelectEnumerableIterator`2[TSource,TResult].MoveNext () [0x00029] in <351e49e2a5bf4fd6beabb458ce2255f3>:0
at System.Collections.Generic.List`1[T]..ctor (System.Collections.Generic.IEnumerable`1[T] collection) [0x00077] in <eae584ce26bc40229c1b1aa476bfa589>:0
at System.Linq.Enumerable.ToList[TSource] (System.Collections.Generic.IEnumerable`1[T] source) [0x00018] in <351e49e2a5bf4fd6beabb458ce2255f3>:0
at Power_Alerts.Alerts.Alert_GeneratorFuelLow.GetReport () [0x00042] in <be3a0ec0cc2e421eb4567318efa8ad51>:0
at RimWorld.Alert.Recalculate () [0x00000] in <99518a644a3e4a7ea3fde566568df84a>:0
at RimWorld.AlertsReadout.CheckAddOrRemoveAlert (RimWorld.Alert alert, System.Boolean forceRemove) [0x00000] in <99518a644a3e4a7ea3fde566568df84a>:0
UnityEngine.StackTraceUtility:ExtractStackTrace ()
Verse.Log:Error (string)
Verse.Log:ErrorOnce (string,int)
RimWorld.AlertsReadout:CheckAddOrRemoveAlert (RimWorld.Alert,bool)
RimWorld.AlertsReadout:AlertsReadoutUpdate ()
RimWorld.UIRoot_Play:UIRootUpdate ()
(wrapper dynamic-method) Verse.Root:Verse.Root.Update_Patch1 (Verse.Root)
Verse.Root_Play:Update ()

I guess it may be related to the generator from Crash Landing, but it's just a guess.

Your intuition was correct, it's related to Crash Landing. I need to get setup again to make changes to fix the issue, but in the meantime if you claim any generators that crash landed the exception should disappear.

@star Or you can just update the mod if you are running 1.3, all instances of unclaimed power buildings throwing errors should now be fixed. Thanks for reporting the issue and let me know if you see anything else!