yes electronic ballasts are going to be the most efficient it has been a long time since i have dealt with ballasts but you deff want one that will carry the curent that your bulbs will use weather it be 2 bulbs at 35 watts each you will need a ballast thats rated 70 + 10 % or the next higher output whichever is there you can also get a ballast thats sized for four and only put 2 on it flr later expansion if that is what you want to do

there aer a ton of types of ballasts out there as far as charecterisitcs there are cold temp starting ballasts there are ballasts the need starters there are ballasts that dont require starters etc...

the basic ballast that you will need is dependant on load and what temps you are going to be running it in aka room temp so i would get norm temp range and get one rated for the load you will be putting on it

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