We’ve all been there: you’re in the middle of a wonderful hot morning shower, when suddenly you’re shocked by a blast of cold water.
Has your water heater failed? Probably not.
More likely, your water heater reached its limit because it isn’t properly matched to the needs of your home. Matching, or sizing your system to its water heating load is the key to keeping hot water flowing for as long as you need it – and to keep your energy bills low, too.
To size a water heater, you need to know three things: the peak demand of your system, the capacity (for conventional tank storage systems) or flow rate (for tankless systems) of your water heater, and the approximate inlet temperature of water coming into your house.
1. Peak demand – Peak demand is the time of the day when you use the most hot water at once. Trying doing a hot water “mini-audit” to give you some idea of how much hot water you use at a given time, using these numbers as a guide:
| Activity | Hot Water Used |
| Clothes washer | 25 to 40 gallons per load |
| Dishwasher | 5 to 10 gallons per load |
| Hand dishwashing | 2 to 3 gallons |
| Tub bath | 20 to 25 gallons |
| Shower or bath | 3 gallons per minute |
| Hand washing | 1 to 2 gallons |
| House cleaning | 5 to 12 gallons |
| Food preparation | 3 to 6 gallons |
2. Storage capacity, recovery rate, and flow rate – If your water heater has a tank, its size is simply the storage capacity of its tank. Related to capacity is the concept of recovery rate, which measures how long it takes your water heater to refill with hot water (that is, how long it takes your hot water to “come back on”). A small unit with a high recovery rate could out-perform a large unit with a slow recovery rate. Manufacturers will usually list a recovery rate for your equipment in its owner’s manual.
For tankless water heaters, flow rate – the speed at which water can be heated and distributed – is the critical measure.
3. Inlet temperature – A third element that comes into play when sizing a water heating system is inlet temperature – the temperature of water entering your home. A house in a colder climate will have a lower inlet temperature than one in a warmer climate –which means more BTUs will be needed for hot water tasks.
A right-sized water heater has the capacity or flow rate needed to meet your peak demand when the inlet temperature is lowest – that is, at the coldest time of the year.
Need a water heater installation in Rhode Island? Contact the pros at Vaughn Oil. We’ll help you size it, get it installed correctly, and be there with professional water heater maintenance when you need it. Contact us today for a FREE estimate!
