First work out what you want it to run! A (camping type) small generator will probably do you for providing lights and small power tools, but you have to remember that the starting load of motors of any kind is a lot higher than that needed to keep them running. If you want to run a typical fridge plus a water pressure system for example, plus a few lights, you are looking at an absolute minimum of about 2kva, and if you want to be able to run this plus a freezer and perhaps a welder, look for at least 6kva. If you want to run aircon as well, you are looking at double this. 
Automatic start is probably not worth the cost unless you need to have uninterrupted power. Electric start is probably not worthwhile for blackout use, unless the person who has to start it is not strong enough. Note that hand starting above about 6kva becomes fairly difficult if you are not pretty athletic. But the problem with electric start is the battery needs to be charged! Can you rely on this to be kept up? Depends how long between blackouts I suppose.
For occasional blackout use, diesel is not worth the cost, but if using it at all consistently, the cost will be repaid - petrol generators use a lot more fuel - running the same load, my ten year old petrol generator uses twice as much fuel as my fifty year old diesel!  
Get a reputable brand - you want it to start when you need it.
Hope this helps,
John
				
			 
			
		 
			
				
			
			
				John
JDNSW
1986 110 County 3.9 diesel
1970 2a 109 2.25 petrol
			
			
		 
	
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