A regular full size electric oven uses much more electricity per hour than a small electric toaster oven does.
The average electric full size oven uses around 5,000 watts of electricity per hour of run time.
So if your electric rates are 10 cents per KWH that means that running your oven for 1 hour would use 50 cents per hour.
If you run your oven for 5 hours then the regular oven at 5,000 watts would use $2.50 per 5 hours of run time.
A toaster oven uses around 1,500 watts so running the toaster oven for an hour would use around 13 cents per hour.
Or if you used the toaster oven for 5 hours it would cost you roughly 65 cents which is cheaper than the regular full size oven.
If you only need to bake a few cookies or something small then a toaster oven is much better but of course if you need to bake something such as Turkey, Chicken etc or something large like a big cake then cooking in the oven would be required.