Cathy hasn't enjoyed a shower in weeks so she and her husband have called in the HVAC Technician for some help.
Replacing your Hot Water Tank
n this skit the homeowners are considering switching from their current hot water tank to an instantaneous hot water tank. Instantaneous hot water tanks take up less room, last longer, provide you with unlimited hot water and most importantly save you money, ie. instead of constantly maintaining the water at 120 degrees fahrenheit, you only heat the water as you require it, so no standby heat loss) provided your unit is sized correctly. Of course the catch is that they are significantly more expensive to install than traditional units
If you decide to make the switch to instantaneous the most important factor is making sure your unit is sized appropriately to meet your demands, in the skit above the “7 Gallons per minute” may be a bit high for the average family, so depending on your family needs you need to consider your flow rate: what is the maximum amount of hot water required at one time (see the diagram below) and what is the temperature difference between the groundwater temperature and the desired output temperature. With cold winters you can expect temperature differences from 75-100 degrees in the winter.
If you decide to make the switch to instantaneous the most important factor is making sure your unit is sized appropriately to meet your demands, in the skit above the “7 Gallons per minute” may be a bit high for the average family, so depending on your family needs you need to consider your flow rate: what is the maximum amount of hot water required at one time (see the diagram below) and what is the temperature difference between the groundwater temperature and the desired output temperature. With cold winters you can expect temperature differences from 75-100 degrees in the winter.
When considering your fuel options natural gas hot water heaters are able to produce a larger temperature rise per gpm than electric models. Most demand water heaters are rated for a variety of inlet temperatures. Typically, a 70°F water temperature rise is possible at a flow rate of 5 gallons per minute through gas-fired demand water heater and 2 gallons per minute through electric hot water tanks. Faster flow rates or cooler incoming temperatures can sometimes reduce the water temperature at the most distant faucets.
Because of the lower GPM’s for electricity and the higher cost of electricity compared to natural gas, natural gas is going to be your natural choice unless you’re in the country and require propane delivered. If you’re looking at just a point of use tank for a bathroom shower, than electric might make sense, combined with awareness of time of use rates in your area and considering solar heating options. But the very first step to reducing your heating costs would be replacing faucets and fixtures with low flow units.
Because of the lower GPM’s for electricity and the higher cost of electricity compared to natural gas, natural gas is going to be your natural choice unless you’re in the country and require propane delivered. If you’re looking at just a point of use tank for a bathroom shower, than electric might make sense, combined with awareness of time of use rates in your area and considering solar heating options. But the very first step to reducing your heating costs would be replacing faucets and fixtures with low flow units.