The Aquanta smart water-heater controller is not a dumb idea for saving energy

Aquanta with app
© Aquanta

Two years ago we covered the launch of the Aquanta on Kickstarter; it's a water heater controller that learns your habits, and adjusts your water heater’s energy use accordingly. But saving energy isn't as sexy as a cooler with a blender on top, so it didn't reach its target.

But now they are back and on the market for pre-order, with a new and improved device that they have been testing for over a year. Water heaters are the second biggest consumer of energy in a home, with space heating and cooling the first. When talking to CEO Matt Carlson he called the Aquanta a sort of "Nest thermostat for your water heater", with the following features that sound familiar to those following the Nest:

Aquanta product attributes include:

  • Convenient control from a smart phone – monitor and change settings from anywhere
  • Smart technology that learns homeowners’ hot water usage behavior and heats water accordingly
  • Manual scheduling for turning the water heater on or off to match a changing schedule
  • Dashboard showing hot water usage and when availability is low
  • Maintenance alerts, including water heater leak detection

But I think the comparison to the Nest does an injustice to the Aquanta. The Nest doesn’t work for everyone or every home or every lifestyle; I know people who have ripped them out because it couldn’t handle families with their different schedules and personal preferences.

Hot water use is different. For one thing, we are creatures of habit and most people shower on a regular schedule. Also if the water heater reduces power and the water cools down, you don’t notice it, like you do when a Nest changes the air temperature and you are home. So the Aquanta has perhaps simpler data to manage, and can turn back the dial on power consumption to a greater degree than a thermostat can. That’s why Aquanta can project savings of between 10 and 30 percent of water heating energy.

Another significant factor is the time of day metering that more and more utilities are using. Where I live, electricity costs 8.7 cents per kWh before 7 AM 18 cents at the peak between 11 AM and 4 PM. with the Aquanta, a water heater can be treated as a sort of thermal battery, heating the water when the electricity is cheap for use when it is more expensive. Aquanta notes that “The economic value of intelligent control of water heaters is much higher when factoring in peak or time-of-use pricing and utility peak demand reduction and similar incentives.”

An unmentioned benefit that I think is actually important is that of Legionnaire’s disease. The low temperatures recommended to save energy in water tanks actually put it into petri dish conditions for Legionella bacteria. The Aquanta can cycle hot enough to kill Legionella, and actually set a balance, as Matt Carlson described it, “between scalding and bacteria suppression.”

I have complained in my post In praise of the dumb home that in a properly built and insulated house, a smart thermostat would be bored stupid. To a degree the same thing can be said of hot water heaters; if they were really well insulated then the standby losses would be less and so would the savings from the Aquanta. However the super-insulated tank would also work better as a thermal battery, making the hot water when the power was cheapest, so it cuts both ways.

Also, in a properly insulated house, the proportion of energy used by the hot water heater is far higher than the typical American house where space heating uses far more electricity than hot water. In a house built to the Passive House standard, the International Passive House Institute notes that “the heating demand for domestic hot water is more significant than that for space heating. Therefore, it is extremely important that the system be efficient and that the heat losses incurred through the preparation, storage and allocation of domestic water be minimised by seamless insulation.“ The Aquanta might make a difference there where they are counting every kWh.

installation© Aquanta

This is not seriously expensive high tech over-promising the world; At $150 to purchase and with relatively simple installation that a relatively competent DIYer could to, this seems to be one of the simpler and cheaper ways to save some electricity without changing habits or affecting comfort. I am dubious about many smart home products, but this seems relatively straightforward and obvious. More information on ordering at Aquanta.

Tags: Energy Efficiency | Smart grid | Smart Home


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