When buying a heater, the pool owner has to reflect on some questions: what size pool heater do I need? This is the most important question that has to be tackled first. Of course, you would want to know how small or big the heater should be, which is enough to provide you with the desired pool temperature when swimming.

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Note that the bigger the heater, the faster the healing process will be. For instance, a heater of 400k BTU can heat the pool two times faster than a heater of 200k BTU only.

But you can also calculate the pool heater sizing to the exact size to get. This post will teach you how to perform that calculation. Plus, we will run through some factors to be considered. Let us get started!

**Considerations To Size A Pool Heater**

Buying and sizing for your pool heater are not just about knowing the size of the pool. It is a bit more complicated than that. To decide on “What size pool heater do I need?” you need to consider the pool volume, your desired temperature, and the coldest temperature that the heater needs to maintain. Other than that, it would help if you also considered the following:

**#1. Speed**

Determine whether or not the heating speed of the unit is crucial to you. For instance, if you do not have a hot tub but a pool only whose temperature remains the same, then speed may not be that important. On the other hand, if you have a hot tub attached to your swimming pool, you would want to consider the speed of the heater to provide you with the desired temperature for the hot tub.

**#2. Pool volume**

You can calculate the pool volume using the formula length x width x depth. After calculating this formula, you will get the approximate pool volume in gallons.

**#3. Water temperature**

In knowing the right pool heater size, you have to determine the temperature you like for swimming. Through this, you can establish the kind of performance you will expect from the heater. The unit should be able to maintain that temperature regardless of environmental conditions. Suppose you have a bathtub attached to the pool. To calculate the BTU requirements, the maximum pool water temperature should be 104 degrees F.

**#4. Ambient air temperature**

If you live somewhere with a hot climate, then the pol has to overcome a different environmental condition than the pool in an area with a colder climate. To calculate the size of the pool heater, you need to identify the coldest air temperature that the heater needs to maintain to keep the pool warm.

**Steps To Calculate What Size Pool Heater You Need**

Now that you are aware of the different considerations when sizing a pool heater, you can proceed to the calculations. Follow the steps below!

**Step #1. Calculate the surface area**

The first thing that you need to do is calculate your swimming pool’s surface area. Many assume that the gallon size is used in determining the heater size. Some websites even use this. But if the pool has a larger surface area, the heat can escape easily, and the heater has to heat more water. As such, you need to get a larger unit to compensate for both the size of the pool and the surface area. In calculating the pool’s surface area, the formula is length times width.

**Step #2. Divide the surface area of the pool by 3**

This will give you the minimum BTU size ideal for the given surface area. Note that the Btu you get is only the minimum recommended size. You can always opt for a higher BTU, especially when you choose a gas heater. It is always recommended that you get an oversized unit for gas heating systems. The pool heater is responsible for replenishing the heat lost at the pool’s surface. Keep in mind that heat loss usually takes place overnight. You cannot compensate for such loss unless you have a solar or liquid cover. Otherwise, having a unit with a higher BTU would be handy.

**Step #3. Considering other variables**

Consider all other variables that can affect the pool heater’s efficiency before you come up with a final decision. This includes the climate, the frequency of using the pool, and solar covers. For instance, if you do not have solar covers, you should opt for a model with 250-300k BTU so that it can account for the heat loss, windy conditions, and evaporation. This is also ideal for those who like night swimming. Without solar covers, you can consider solar blankets. It is cheaper to invest than to pay for a bigger pool heater. You may also want to read about pool heater sizing.

**It’s A Wrap!**

It is not easy to know the answer to the question: what size pool heater do I need? But if you follow the steps above and put into consideration the different variables mentioned, you can get the right size pool heater that will suit your needs. That’s it for this post. You may want to read related articles; know how much does it cost to install a pool heater and what is the best pool heater. Thank you for being with us!