Bosch AE125 PowerStar 4 GPM Indoor Electric Tankless Water Heater

PowerStar water heaters bring the performance of tankless models to situations where an electric unit is preferred. Compact and powerful, the AE125 can supply enough hot water to support one major application.

• Electric tankless water heater; for climates with annual groundwater temperature below 60 degrees Fahrenheit
• Provides 4 gallons of hot water per minute; average energy-efficiency rating of 94
• Includes solid-copper heat exchanger
• Includes one water heater
• 15-1/2 by 15-1/4 by 4-1/2 inches; 22 pounds; 10-year limited warranty on heat exchanger; 1-year on parts

It delivers hot water based upon a system that measures the incoming water temperature and flow rate and then “calculates” the number of elements (it actually has 6) that it turns on to provide an outflow temperature based on the setting of the temperature control. This system is not satisfactory for a water supply which varies in pressure, SUCH AS A WELL, as the unit itself provides substantial resistance to flow and thus the flow rate through the unit varies and thus the temperature of the outgoing water. This causes the delivered water to vary widely in temperature, from VERY HOT to VERY COLD. The unit would be improved if it was “smart enough” to not only measure incoming temp, but, also, outgoing temperature and flow rate and maintain the outgoing temp at a constant level.

The unit has a flow sensor, which will shut the heaters off at low flow, so, therefore, if you wish to have a small amount of hot water flowing into your sink for shaving purposes, the water will not be heated at all. This “Feature” also has considerable influence on the use of “low flow” faucets.

The unit apparently switches one or more of its six elements on or off as it attempts to heat the water. There does not appear to be any partially on for any of the elements. This leads to the problem of “stepped” heating of the water. And because the unit measures flow in and calculates the outgoing rate, if the water is mildly too hot or too cold, simply changing the mix at the faucet does not necessarily result in mild changes in temperature, a tiny change at the faucet can cause one or all of the elements to switch off resulting in a dramatic change at the faucet. AGAIN an argument for sensing the outgoing temperature and maintaining it by modulating the elements for a smoother temperature curve.

Bosch GL2.5 Ariston 2-1/2-Gallon Point-of-Use Indoor Electric Mini-Tank Water Heater

Installing an Ariston electric mini-tank water heater under the sink puts hot water right where you need it at the point-of-use. Lightweight and compact this heater is available in three space-saving sizes: 2.5, 4, and 6+ gallons. These heaters are aesthetic on the outside, glass-lined on the inside, and offer superior insulation for higher efficiency.

• Stores up to 2.5 gallons of water to supply hot water for a single sink
• Easy, space-saving installation and draws power from standard outlet
• Works independently or in line with a larger water-heating system
• Glass-lined tank for longer life
• Dimensions: 14-by-14 by-10-1/4-inches; Weight: 16 pounds; Electrical: 120 volts, 1500 watts

It is very easy to install and will fit in your kitchen cabinet. More challenging might be having an electrical outlet that can be dedicated to the water heater, which takes 1500 watts, and will certainly blow your circuit every time if you try to combine it with a dishwasher, microwave, toaster, or anything else “thirsty” (most things are) in the kitchen.