An ozonator provides supplemental oxidation to get rid of bather waste and also to kill some pathogens faster (but they have to find their way to the ozonator via circulation and cannot be stuck on spa surfaces). If you use the spa every day, then having an ozonator may cut your chlorine usage roughly in half (if you are using bromine instead, it will cut that usage down as well).
On the other hand, if you don't use the spa frequently, then an ozonator will increase chlorine demand, perhaps doubling it (either from oxidizing chlorine to chlorate or having faster chlorine outgassing) so instead of losing 25% of FC each day when the spa is not in use you would lose 50% each day with an ozonator.
The extra chlorine demand would be having 2 ppm FC per day instead of 1 ppm FC per day assuming you were trying to keep 4 ppm FC as your chlorine level. However, it might not be as bad as I describe since it depends on the strength of your ozonator so you might as well try things out for a while to see how it goes.
My tub has an ozonator. I would also recommend leaving it hooked up. My FC consumption is minimal (see attached log) and our usage is about what yours is. However, with that being said when or if it quits working, I probably will not replace it since the BBB method has served me well ever since I learned about it.
I'm a new tub owner - one week today - we have an ozonator, and I'd say over the past week I've put about 6 tsps of chlorine granuals in our tub and I've not been able to get any FC reading on my test strips. Last night I tested after we got out - the total chlorine was higher than the free chlorine so I put in 2 tsp of non-chlorine shock as suggested by the book that came with my test strip kit. I read on another forum that ozonators use up FC - how much chlorine do I need to get a FC reading in the safe range?
Just about to buy a softub and I can have the option for the ozone unit, I'm almost certain I will have it installed and it looks like I can turn it on and off as required. In most cases would use say it's a good idea? I have never owned a hot tub before so really unsure how this all works. They will install the softub and show us how to use it and supply a starter kit of chemicals to get us going.
Ozonators are good if you are using the spa every day or two. They aren't good if you are using chlorine and only use the spa infrequently, once or twice a week or less. The reason is that while ozone oxidizes bather waste, it also oxidizes chlorine so it decreases chlorine demand from bather waste while increasing daily loss in between soaks. Which one wins out depends on your bather load (how many bathers for how long how often).