Dual gas/electric residential water heater?

Is there such a thing?

We have a gas instaheat hot water system running off LPG bottles that, sadly, has a dying thermostat. (Sometimes it works, most often not. Repair is not an option, plumbers just wanna replace. Modern throwaway system. :sigh: )

The instant heat is nice, but constantly refilling LPG bottles... well...

I'd replace with electric except that the house is untenanted for long(ish) periods and all power is turned off for that time. I'd love it if there was a hybrid in which the gas only kicked in when the electric tank was below temp.

Does anybody know if such a beast actually exists? Or can at least suggest search terms for Google that don't throw up pages and pages of just Gas or Electric, or Gas VS Electric?

Go for gas boosted solar. The booster will operate the same as your current one, but you have the bonus of pre heated water. Saves a lot of gas, and that stuff is getting very expensive now. We turn the gas off during the summer.

Hooroo.

All you're really talking about is putting an instantaneous gas water heater on the hot water outlet pipe of a conventional off-peak, prime tariff or heat pump electric heater. If you're going to go to that expense a gas boosted solar system would be the way to go. Being in Katoomba a system with the solar heating and household water supply sections separated, so that an antifreeze mixture can be run through the collector panels would be best. I've seen way too many failed collector panels to have any faith in anti-frost valves. :C

With the way that solar electricity install costs have come down save the grief and expense of solar heated water and just install an electric storage unit with electric solar panels. If you put in a diverter that will divert any spare electricity to the water heater instead of dumping it into the grid you get cheap hot water and save on electricity bills.

See solar diverters.

This got me thinking outside of the box I'd locked myself in. ;)

Gas boosted solar sounds ideal for our budget. More research is needed.

Thanks fellas!

There used to be rebates for first timers. Not sure what the go is now. Have a bo-peep on the government sites.

Hooroo.

We bought a older small-medium house in Alexandra Vic nearly three years ago. It had originally had a combustion stove and wetback low pressure system with mains backup installed but had had a kitchen upgrade about 5yrs prior, so the stove and HWS system went, replaced by a Bosch 26e instantaneous gas unit. Everything else in the house is electric, and the unit runs through a 45kg LPG cylinder ($115) every 3 months to heat water for the two of us. We have a two cylinder auto change over system installed, so do not have hassles when cylinders run out, it switches automatically to the second cylinder and keeps working. Once the cylinder has run for 2 months we glance at the indicator on the autochanger weekly, and when we note that it has switched, we contact our local supplier and have the empty replaced.
We are with Supergas, and pay $54pa rental on the two cylinders. When we were in Melb and has Natural Gas for a hotplate and Aquamax 135 SS storage system, our quarterly gas bills where higher than they are now. The modern gas instantaneous don't have a pilot light running constantly (use an electric igniter instead), and are automated to control gas flow to heat the required water flow to the required temp, so are much more efficient that older ones are.

We will be building a new house this year and have specced to have 2 of these heaters installed, purely because there is a fair distance between the kitchen and ensuite at one end of the house and laundry and bathroom at the other, and I would rather have the pain of paying for a second HWS now than be always flushing out an extra 15m or more of hot water line to get 5L of hot water. My only complaint about the complete system we have in this house is that the lagging is off most of the pipes so they loose heat quickly when not flowing and we waste water running taps till we get hot flowing out, the localised dual system that we are moving to will eliminate a lot of that waste, without using more gas as only one heater will be firing at a time.

Not sure if you'd consider electric heat pump, but we've had one of these in NSW Southern Highlands for about 15 years and still going strong. Looks like a conventional tank, but with an extra "stage" on top containing compressor and fan. No roof mounted panels or other gubbins to worry about. Draws in "warm" air (warm relative to the refrigerant that is....works happily on outside air even in the depths of winter), transfers heat into water, expels cold air. Only runs when the water needs heating (not really a storage heater per se), and could be turned off altogether when not in use. Our power usage supports the claim that it only uses about 1/3rd the power of a conventional electric water service; has been very cheap to run, and completely reliable. We never run out of hot water either.