Changes

Many diesel stoves have a similar feature. A water jacket heats the hot water, which is then circulated through coils in the hot water tank. Standard electrical elements are also provided as backup. Features to check for in a water tank are stainless steel, well insulated (R16 minimum), flow rate, coils in the bottom (where the cold water sits!), and a winter drain cock.

Selecting the right size for a tanked heater is the usual head-banging exercise. Based on the industry guidelines in [[WaterCapacity]] (7 gal per person to as high as 17 gal), you would select a capacity of 80 gal, based on six people @ 13.3 gal/person.

Using a flow-rate calculation yields a similar result. If we multiply the flow rate by the number of minutes the appliances will be open, say two 10-minute periods, this equates to a tank capacity of 95 gal. For five minute showers, the capacity required is 48 gal. These numbers make a 40-gal tank seem more reasonable, but there is still the issue of recovering in time for the second set of showers. Tanked heaters don’t recover that fast.

Water tank heaters cycle continuously and are energy-rated in kiloWatt-hours/year (kWh/y). A typical 40-gal tank will consume 4,773 kWh/y or 545 Watts/hour, which is 4.95 amp-hours (AH) at 110 VAC. One example delivers 25 GPH or about 5 GPH/A. Peak power demand is 3,800 W, which will take up a good chunk of a 5,000-W inverter.