Hot Water Heater on electric or gas

Winnebago has "Motor-Aid" on a lot of their motorhomes. A hose carrying antifreeze from the engine is routed to a pipe in the water heater that carries the antifreeze through the center of the water heater, heating the water as you drive. When you get to the campground, the water is pre-warmed, if not pre-heated.

The MH I sold today had that feature. It worked.

I disagree with a lot of the posts here.

To burn gasoline to make electricity to turn around and make heat is generally inefficient- particularly with a small engine.

Gas engines are not all that efficient...lots of heat blows out the exhaust, lots of heat blows off from cylinder heads and crank case and etc. Then your generator even has a cooling fan, and the wires to the water heater can heat up...lots of waste.

Lots of good heat that could OTHERWISE been used to heat water.

The water heater isn't 100% efficient either, but the burning gas goes 'directly' to heat up the water, instead of being blown off from a cylinder head, muffler etc. (At least it goes a lot MORE directly).

Now, I also get it that there's additional layers of complication. "The generator is already running"...that might move the scales some. LP from the camp store can sometimes be pricy versus gasoline- and $ wise? Who knows.

Also, there's a lazy factor...filling the gasoline tank can be easier than unhooking the LP tank, hauling it to the refill place, hauling it back, reinstalling it.

Still- small gasoline generators operate well below 50% efficiency while water heaters are generally above 50% in their energy conversion / transfer.

This is a geeky and pure engineering thought, but I've always wondered if there'd be significant energy harvested (and efficiency increases) if an 'exhaust pipe' could be routed into a boiler (or water heater)...Then we'd really be on to something :-)

The water heater rods typically draw 1200 watts. That's a large additional draw.

After market kits such as the "hot rod" are lower wattage.

wildtoad wrote:
If you are running the gen anyway to power the AC or charge batteries the wh will not add much of an additional draw. I would not start the gen just to get hot water.

If you're camping/snowbirding for months at a time and have to pay separately for your electricity, how do you determine which is more cost-effective or efficient?

Thanks all... It confirms what I had thought, and what I was already doing...

DutchmenSport wrote:
If you are powering with a generator, you'll probably want your water heater running on gas.

If you are plugged into shore power, it doesn't really matter which way you run your water heater, or even if you run both. Gas will recover faster than electric, and Gas will heat from cold faster than electric too. But gas and electric together are best for fastest recovery.

It's all a matter of how fast you want to heat your water and the available of electricity (shore power or generator).

exactly what we do.

If you are running the gen anyway to power the AC or charge batteries the wh will not add much of an additional draw. I would not start the gen just to get hot water.

Hi,

If there is enough wattage I would run the water heater on electric. But make sure brown outs are not happening when the compressor starts. If there are, then move the water heater to gas.

If electric is included in our camping fee, we use electric. If we pay electric . then we use the formula that has been posted to figure out whether the electric rate we are paying vs cost of propane is cheaper, then use whichever is cheaper. If using propane we would let it get hot in the morning for showers, then shut it off. Turn it back on after dinner for doing dishes, then back off for the night. The water stays warm a long time without running the water heater, unless it's really cold/windy out.

Put the water heater on propane AND electric. When the genny is running, electric will keep it hot. When not, propane will keep it hot. If your crew takes multiple showers while the genny is running, hot water recovery will be faster.