I posted this to the Escapees forum, but think some of my fellow Allegro owners might be interested...(There were "mixed" reviews):

I thought I wanted the Hydro Hot system in my next MH and I got one. (For those not in the 'know', a Hydro Hot is the no longer manufactured little brother to the Aqua Hot, and, over-simplified, they use a diesel burner to provide hot water and heat to the RV, there is no LP water heater or LP furnace). I haven't made up my mind yet whether it was a good idea or not. Leaning towards not! For one thing, it is stinky sometimes, and if I was a neighbor to me I'd probably move to another site! The noise is no worse (maybe quieter) than LP furnaces. The heat is wonderfully even, and I can set the bedroom to be a different temp from the rest of the MH. Hot water in the shower for as long as you want, water is heated as it is used. Aqua Hot's advantage over the Hydro Hot is that because of the larger tanks, the heat doesn't 'quit' when the hot water is being used.

Getting accurate operating costs is not an easy task. The burner does not have to operate all the time. The manufacturer says owners report between 1 to 3 gallons per day use, and the rate used when the burner is operating is about .5 gal per hour.

I'm furnishing our figures for anybody interested with the costs of operating the system: For two months we've been in Apache Junction, AZ. It's been cooler than usual this year, but not 'cold'. Most days haven't required heat. We turn on the heat in the evenings if we're home, but turn it totally off at night. So it essentially runs about two hours in the morning, and starting about 7 PM until bedtime, which could be after midnight. Sometimes, rarely, we'll turn it on to heat for an afternoon shower if we missed the morning one. We filled the motorhome with a full tank on December 5th, and filled it again today, February 1st. Subtracting mileage to the station, our fuel usage for the 2 months was 52 gallons, (26 gals per month), or .9 gals per day for 58 days.

Just in case you were wondering....


If anybody else has tried to 'quantify' their AQ or HH I'd like to hear about it.

So what would the cost be for a typical LP system? Do you have a total hours number -- so $$ per hour can be compared for both?

That was great information Gary. I had never seen anyone compile their real life useage before.

We also debated between propane and AquaHot when we were comtemplating between ordering a Phaeton or Bus. Both LP and Aquahot have their advantages and disadvantages. LP burns cleaner with no odor and the furnaces usually require less maintenance. AquaHot offers the unlimited hot water and even heat.

Without going through all the pro's and con's, since the topic pertains to fuel useage, one important item to mention is the BTU content of the two fuels.

1 Gal of Propane contains 91,600 BTU of energy

1 Gal of #2 Fuel contains 139,000 BTU of energy

When considering fuel consumption engineers calculate the BTU loss of a residence, calculated to the 1 Million BTU.

So hypothetically, if 1 Million BTU kept your coach warm for 1 week, you know how many gallons of each fuel are used to generate the 1 Million BTU

For Propane, you'd burn 10.917 gallons, and you'd burn 7.194 gallons of #2 fuel oil. Sooo...during the same time period, of heating with 1 Million BTU, you'd burn 3.723 more gallons of Propane if the efficiency of both heat sources was the same. (which it probably isn't)

Gary's experiment determined the burn rate for fuel, so if (and it's a big if) the efficiency of the two heaters was the same, you'd use a little over 1-1/2 times as much propane for heat.

BTU compariswion -- why didn't I think of that -- good job!

Can you extend that comparison to cost for each fuel type?

My question would be why didn't you just switch over to the electric side of the Aqua-Hot? When I'm parked and pluged in I just hit the switch and run the A-H off of electric.

Also the smell you mentioned might mean that your system needs to be adjusted or burner needs servicing, something you should do every year.

For cb5300: Guess you missed the part where I said I have a Hydro-Hot not an Aqua Hot. The HH has a much smaller tank than 2 of the 3 AH's.(FYI, the HH is now redesignated as the smallest AH). The electric element isn't able to keep up with on-demand hot water or heat...if left on a while, it will provide enough for a semi-large load of dishes, that's about all. Be happy you have the Aqua Hot and it's advantages, but I do like my HH anyway. I have the parts and I'll be installing a new nozzle and fuel filter soon as I can. Thanx for your response.

Cute kid in your avatar!

Even if it couldn't keep up, I would think that it would still take some of the load off the diesel burner therefore saving some on the fuel. But you're right, I am glad that I have the Aqua-hot.

A lot depends upon how well insulated et al and the outside temps. We have the HH and find that if the outside temp is >40 then electric only will heat the caoch fine and is good for one shower and then wait...if below 40 we turn on the diesel as well

Anybody know exactly how large the hot water tank is on an HH? We've tried to heat with just the elec element, but it just couldn't keep up. Think we might get a shower out of the elec if we were some stingy with the water...but letting the water run on diesel can certainly spoil a body and make you think twice about a Navy shower!

We were parked next to a MH with either HH or AH, I can't remember which one, but the smell was rather offencive when it was on. We would go inside & close all our windows when it was on.
When we are hooked up to electric we usually run our basement heatpump. It saves on propane and heats evenly & quieter.