Tuesday, March 11, 2008

On-Demand Water Heater

These are all the rage these days. I guess they have been around in Europe for a long time (we Americans are a little behind the times in many facets of Earth-friendly living it seems), and so we bought one. With the planned solar photovoltaic (PV) system, we went with an electric model made by American Tankless.

These are kind of hard to research I found, and most of the information you will find at this point will be on the manufacturer's websites, which of course all boast that their model is the best. I bought the American Tankless one because it came with a lifetime warranty. Who knows if this one is any better than the next one. Home Depot and Lowe's are pretty much useless sources of information, and last I checked only Lowe's carried a model in stock and it was a natural gas model.

Anyway, These come in oil, gas/propane, and electric models. The basic gist is that this is a little wall-hung unit that is never running or maintaining a vat of water at a certain temperature. You open a hot water faucet, it turns on. You close the faucet, it turns off. Very nice. With an electric model like mine, it consumes no electricity, ever, unless you turn on the hot water. That is pretty sweet. When it does turn on, it requires a 125 amp breaker (your house needs to be juiced up to run one of these things...like an electric oven or electric heat), but even without the solar panels installed yet, the water heater only raised our electric bill maybe $10-$15/month (and is 98.5% efficient). Admittedly, there are only two people showering in our household, but considering at $10/month, that's only $120 bucks a year to run the thing. I'm guessing a standard tank-style electric water heater uses a lot more electricity than that. On-demand models do cost more than a tank heater, but since water is never sitting in them, they should last longer.

The big selling point of on-demand hot water heaters are that they don't run except when you need them to. When you are off at work all day, there is no quantity of water having its temperature maintained. This saves electricity if you have an electric model, and obviously oil or gas if you have those models. The oil or gas models can typically vent right out a wall as well, and don't need to tie into the chimney. Electric ones could even be (and often are) installed under a sink or in a closet behind the shower... Doing this makes the heated water have less distance to travel to the place it is needed, and thus retaining more of its heat.

Ours is installed in the basement and is only pushing water up to the first floor right now. I'm guessing once we renovate the second floor, we may install a second on-demand heater upstairs.

I should note, this little thing is ONLY used for domestic hot water. Not for heating the house. I should also note that this type of water heater can be installed in-line with a solar thermal or geothermal system, so that those systems pre-heat the water before it gets to the electric water heater. If the pre-heated water is hot enough already, the water heater won't even turn on. If it needs to come up a couple degrees, the water heater will kick on as the water travels through it. I would imagine a solar thermal system will be added to our arrangement sometime in the future. Gotta get the solar PV system up and running first. More on that soon. It shouldn't be long now.


Anonymous said...

Follow-up... This unit has been nothing but trouble and I was scammed by people who promised a lifetime warranty then closed up shop, opened as a new company called American Heat, fleeced people there and now are operating as EcoSmart... I have since read that all of their heaters are stolen and unfinished technology, which is why mine gives me 5 minutes of hot water before overheating and gong ice cold. I am currently looking into legal action against these scam artists.

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