Our Propane Hot Water Heater
Hawaii leads the lot by being the most expensive state for electricity (34.43 cents) while Washington is the cheapest state (9.35 cents).
Because of this, we try to find ways top cut costs and some ideas are better than others.
We have a massive push to be energy independent and that means lots of solar and other types of power including wind, geo-thermal and wave action, etc. Beside secondary heating of water, many of us already have somewhat warmer water coming out of the spigot. In rural Hawaii we have PVC, HDPE and metal pipes which lie above the ground. This is because it is very expensive to dig through lava rock to hide pipes. Air temperature is 70-85 degrees daytime and only 60-something at night for most of us. That means that water near the house on a long run is already warm.
One option is to put Geo-thermal units on the roof. They may be elaborate units or just pipe zig-zagging in the sun. This may go directly to a faucet or be a pre-heated input to a conventional water heater.
In my case I decided to buy a propane on-demand hot water heater. I got it on Ebay from someone who ordered the wrong model. They needed a unit inside and this is an outside unit. Thus, this unit does not need to be vented. It is a Rheem and not the largest model, but then again, it is a small family here.
Although we are doing lots of plumbing to add a kitchen downstairs, I came up with a simple installation. There was a laundry tub where the heater is now. I took the existing faucets out and piped the cold water to the input of the tank. The output (hot water) went into where the hot water faucet was. When we removed the electric hot water inside, we just capped the cold and hot pipes. Water doesn’t really care which direction it goes through the pipes.
The unit is powered by a bar-b-que propane tank and a properly sized regulator. The unit takes a lot less flow than a bar-b-que. The 120 volts pulls in the relay and starts the ignition for the burner. When the system sees that hot water is called for, it triggers the propane flow and ignites it. There also is a remote thermostat-type unit which allows you to adjust the water temperature so that you could set it low and press the button to get hotter water.
When you turn on a hot water faucet, the unit kicks on almost immediately and starts warming water as it passes through the unit. This means that if you have a tendency of turning on hot and cold just to wash your hands, wait for the warm/hot water to flow to you before turning things off, so you are not wasting propane and needlessly starting and stopping the unit.
A drawback I knew about happened a bit sooner than I expected. Since it requires 120 volts, you have no hot water during a power outage. This happened a couple weeks after installation when we lost power for a few hours. The power draw is minimal, so I will wire it to one of my UPS (Uninterruptible Power Supplies) which supply power to my TV and lights. Today we ran out of propane and hot water stops instantly. I switched tanks in 3 minutes and the one in now has a meter to show how much is left.
It will not take long to recoup the cost on the unit as refilling a small tank of propane is $21 or less. So far we think the unit is using $21 worth of propane in a month but we are not sure how full that first tank was. I believe that my old water heater was a good portion of my electric bill so I am hoping for a reduction in electric cost.
One other thing we did was cut most of the old copper water lines from the house and replaced them with PEX. The pipe and connectors and a bit pricey but it requires no glue or torches to install. The only other drawback is that after we started replacing all the pipes with PEX, I saw a Youtube video which suggested making the hot water pipes larger to reduce time to get hot water across the house. Then again, it is a small house and most pipes are fed from a central location, making it a star rather than long lines with multiple offshoots.
So, I write this in case someone is wondering how this works and if it is for them. If you look into it, ensure you take costs and sizes of pipes and the size of the unit to ensure proper pressure and hot water.