It seems as if here lately I have been running into many 40 gallon electric water heaters in my inspections, especially in new construction and rehabs. Depending upon the application, I write these up as being improperly sized. Here’s why.
The selection of a particular type hot water supply system for a house is determined by several factors including the utility connections available, utility rates, hot water demand, and builder or owner preference.
There are several methods used to calculate the hot water demand, each possibly giving different results. No one single method is a perfect indicator of the actual hot water needs. Actual demand can vary widely depending on the particular house and occupancy. The number of people living in a house, occupant ages, lifestyles, work schedules, and the number of appliances using hot water are all factors that can significantly affect water usage.
Most households use the highest volume of hot water during two peak periods every day. These peak periods are when the heaviest water draw from the hot water supply system will occur, and ultimately dictates the capacity requirements of the system in most cases. The common peak period for most households occurs in a two-hour period between 6:00 - 9:00 am or 5:00 - 8:00 pm each day. Regardless of the adequacy of a water heating system during off-peak periods, inadequate hot water during peak periods will lead most people to believe that there is a hot water supply or capacity problem.
Keep in mind too that not all water heaters are made equal. Nor, are all households the same. Hence, the specific water usage patterns and water heater design and capacity specifications must be considered to determine what water heating system will be most appropriate for any particular situation. If you are running out of hot water at various times of the day, you may need to have to change your life style or have a specialist in the appropriate trade further evaluate the size of your water heating system.
I have attached the following guide to give a reference for selecting the appropriately sized water heater based on the number of bedrooms and bathrooms. I hope that this helps.
Below are links to other sites or articles that I have written: