Choosing the right size hot water heater

19 Aug, 2020

So your old hot water system is broken and not worth fixing or you’re looking to upgrade a smaller unit to a system with greater capacity.

In this article we’ll look at what are some factors to consider when determining what size water heater you need for your household. Heat pumps, solar hot water and instantaneous hot water units are increasing in popularity but today we’re going to focus on the classic tank or storage style hot water system. If your interested in reading more about the pros and cons of each of the different types of systems take a look at our general hot water system upgrade article.

If your seeking a hot water repair technician in the Ipswich region you can get in contact with us to discuss your concerns and the options available to you, and of course fix or replace your hot water heater.


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Choosing the right size hot water system

Many manufacturers provide over simplistic recommendations and guidelines for choosing the right size storage hot water unit for your household. Generally, they provide recommendations based on the number of people living in the household and or the number of bathrooms in the household.

These recommendations may work for some people, but it could also lead others to choose an oversized unit. What’s the problem with an oversized unit? Not only do larger hot water storage units have a greater upfront cost, but they are also incur increased running costs due to a larger volume of water which needs to be constantly kept heated. There’s no use having an excessively large hot water unit if you never get even close to using it to it’s full capacity.

When determining what size hot water storage unit you actually require it all comes down to how much hot water you use during the day and when you use it.

Since storage hot water systems contain a limited volume of water you want to ensure that your hot water usage habits are within the tanks capacity. It can take anywhere from 30 minutes to 90+ minutes for a hot water tank to fully heat up so you want to ensure your tank has enough capacity to meet your hot water needs.

• How many people in your household?

• How many people in your household?

• What time do they take showers?

• What is the average duration of showers?

• What is the flow rate (L/min) of the showerheads?

• Do members in the household take baths? If so, what is the capacity of the bath?

• What other appliances in your house use hot water? (e.g. washing machine, dishwasher)

• Is hot water being used whilst other members of the household are showering? (e.g kitchen sink, dishwasher, washing machine etc.)

Keep in mind it may also be possible and relatively easy to make some simple adjustments to your household hot water usage habits to suit a lower tank volume. For example, if the dishwasher or washing machine uses hot water, they could be operated at a time when showering is not taking place.

run your waashing machine when hot water is not needed

Hot water usage calculation example

Here’s a little case study example to help illustrate how your can make little changes to your hot water usage and save on your gas or electricity bill. 

There are four members in the Jones family. They each take showers in the evening after dinner. Their showers are on average 5 minutes in duration. Their shower is fitted with a water saving shower head meaning that the maximum flow rate is 9L per minute. Therefore, each member uses 45L of hot water per shower. The family uses a total of 180L of hot water for showers each evening. They use an additional 20L of hot water to wash the dinner dishes. In total the family uses 200L of hot water on a typical evening.

Consider if two family members preferred to shower in the morning, instead of all four showering in the evening, this would reduce the evening hot water consumption to 110L. Given this scenario the family could opt for a smaller hot water storage unit saving them both in up-front costs and reduced running costs for the life of the unit.

There you have it some thoughts to consider to help you choose the right hot water heater for your families needs. Doing some simple maths could end up saving your family some nice extra cash for years to come.


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to replace your old water water system? If your located in the Ipswich area why not get in touch with us for a friendly free quick quote, or check out more our full range of hot water services.

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