Hi tub-time,
I don't have a ton of time to respond with a long answer right now, but I can give you a short answer. Don't trust the Bullfrog documentation! As you mentioned, they assume $0.10/kW and the test they did was in standby mode, meaning the jet and filter pumps weren't on. So, if all you want to do is fill your tub and look at the pretty water every day then you can use their baseline numbers. However, if you want to actually get it and use the jets, then you can throw the brochure, and their claims, out the window.
I have an A8 and my electrical went up about $125-$175/month depending on if it was a normal usage month or a month where I emptied and refilled the tub. It takes a lot of energy to bring ambient air temperature water up to 100 degrees! On my A8, the heater will raise the temperature about 4 degrees/hr. So, if you have 70-degree water and want to raise it to 100 degrees, it will take over 7.5 hours to do that with the heater (and power) running at full throttle the entire time. And mind you, I'm in the Central Coast California with probably similar electrical rates and we rarely drop into the 30's at night during the winter. So, in terms of outside environment, I'm probably as ideal as you'll get during the winter.
Since you're looking at an A6L or A7L you won't use as much electricity as I am with an A8, but it's still going to be a lot more expensive than the $12/month that Bullfrog is advertising.
Also, while it seems like I'm bagging on Bullfrog, I do like the hot tub and one of the reasons I picked it was because of the insulation and energy efficiency. If my electricity bill is $125-$175/month with a Bullfrog, I can't imagine what it would be with another hot tub that isn't as energy efficient.
What Bullfrog, and every other manufacturer needs to do, is post real world energy usage stats. For example. If you use both jets on high for 20 minutes a day, twice a week, and the filtration pump runs for 4 hours a day, this is how much energy you would use in a month. It would also be nice if everyone also published individual stats like: Each pump on high will chew up 3k of power, so 6kW total. The filtration pump uses 200 watts. The heater uses 7kW and typically will average 2 hours a day over 30 days based off using it 2 times a week in 70-degree weather for 20 minutes each time.
This is longer than I wanted, but it gives you an idea. I'll follow up with more when I have more time to write because I actually hooked up an Emporia circuit breaker current
measurement device to my breaker box so I can measure the energy I'm using on just the hot tub circuits. With this device, I know exactly how much energy the hot tub is using every month, day, hour, minute, and even real time every second. I probably went overboard on this, but I wanted to know the exact breakdown on things so no-one, including Bullfrog, can come back and say well, everyone's energy fluctuates from month-to-month so how do you know it's the hot tub that's raising your bill so high. With this device installed, I know with 100% certainty how much the hot tub is costing me every month to use and it's nowhere near the $12/month Bullfrog claims. So definitely throw those numbers out the window :-)
Hope that helps for now and I'll follow up when I have more time to respond.
