We use propane with our 48" Viking. It seems fine. I believe, when I was looking into this almost 4 years ago, other brand(s) (Wolf for one) claimed that no btu's were lost with the switch from natural gas to propane. This wasn't true with Viking. I have nothing to compare our range with but I never find myself wishing I had more btu's.

You would only "need" dual fuel if your propane tank was close to the limit of it's delivery potential for the other gas appliances in your home. Upgrading to a larger propane tank would seem to make more sense at that point, as if it's marginal already, you're probably already having some issues with peak demand times.

I started out looking at dual fuel ranges, but determined that all gas was best for this house. I bought an American Range. I spent some time looking at DCS based on a blurb I ran across where the person had propane and several appliance places recommended DCS because of the higher BTUs. She was thrilled with her range. I agree that it makes sense to go dual fuel to cut down on the propane usage. Besides what's not to like about electric ovens?

We have a 36" Bluestar and use propane. No issues.

I do not know why you need dual fuel; Bluestar comes with natural gas or propane options--you need to specify. Unlike other manufacturers, there is no conversion kit, so you do not lose any BTUs with propane.

Make sure your propane tank has the pressure specified by the manufacturer. Do call Bluestar with your concerns--they'll steer you correctly.

We decided not to go with dual fuel (when looking 18 months ago) because they all had closed burners, and we wanted open burners. That might be different now.

I installed a 48" DCS in my last house (full remodel). Using propane. I had a giant propane tank that I never needed to refill in those 3 years. I chose it based on Rosengarten and its BTUs. I never had a single problem with it that needed to be fixed. But I don't think I would go DCS again. Firstly, because you can get 18,000+ BTUs from other ranges these days (my DCS was 3 years ago). Secondly, because the flame diameter was too darn wide for anything less than a 10+ inch cooking pan. Yes, I know I can turn it down, but what is the point of 18,000 BTUs if you have to turn it down because your pan is too small??? I have 25 year old LeCreuset pans that are still going strong and I like using them. The only way I was able to crank up my DCS was with a wok, a stock pot or my enormous LeCreust dutch oven. Or my copper crepe pan, but that would ruin the crepes! Also, the grates sit much closer to the flame, so the "flame spread" or whatever it is called is greater. Basically, you have to use really big pans or use really low (relatively speaking) heat. Simmer worked great. I could wok with the best. I had 4 burners, a grill and a griddle. Rarely used the grill because my @#$% Vent-A-Hood that the salesguy assured me would be more than adequate was not. Plus the grill heat was kind of uneven. The griddle took FOREVER to heat up and was very hot at the top and very not at the bottom. Plus it was a pain to clean. So I didn't. I can't comment on the DCS ovens, as I had the rangetop and wolf double ovens (which I loved, but in retrospect not sure they were worth the extra money). There are currently other ranges that get you the BTUs with better flame configuration (Blue Star, Dacor, and Wolf all gas come to mind...).