what size heater do I need for my pool
Pool Knowledge

What Size Heater Do I Need for My Pool?

As a pool owner, you might ask the question: what size heater do I need for my pool? In this post, we are going to answer this question. In this post, we will help you perform the calculations and figure out the appropriate size of the heater for your pool. But before that, let’s discuss what you need to know about choosing a heater.

Before you buy a pool heater, you have to take several important factors into consideration. You should know how big or small a heater you need to buy for your pool. A small heater does not heat your pool as fast as a small heater. But that does not mean that bigger is better when it comes to choosing a pool heater

What You Need to Know

For many pool owners, natural gas or propane-fueled pool heater is necessary. Whenever you swim, you can enjoy a comfortable and warm pool. Your swimming season can be drastically extended with a heater. But swimming pools come in different sizes, and that is why they require heaters of different sizes.

A pool heater can be used in two ways. When you are not using the pool, you can let it cool down. Then you can switch on the heater to bring the temperature to a comfortable level and start using the pool. The second way to use a pool heater is to constantly run the heater. If the temperature of your pool is at a steady level, you can use the pool at any time.

You can use this pool heater in any of these ways. A high powered pool heater is necessary if you want to let the pool cool down every now and then. The reason is simple: you will have to heat the pool more quickly. And if the pool is heated quickly, you will not have to wait for a long time to take a swim.

“What size heater do I need for my pool?” you may ask. An important thing of consideration is that the size of the pool heater should be consistent with your requirement. If you want to heat the water quickly, you will have to use a relatively large pool heater. A smaller heater is probably a good choice if you want to keep the pool water warm all the time. Now we are going to show you how to perform the calculations.

Types of Pool Heaters

There are 3 main types of pool heaters. But they all are measured in BTUs. This is a unit of heat measurement. The amount of heat is indicated by this unit.

Gas pool heaters are highly powerful pool heaters. They can provide up to 500,000 BTUs of heat. If you have a large pool, you can consider using a gas pool heater. Read some reviews and you will learn that most pool owners are in love with gas pool owners.

An electric heat pump runs on electricity. However, it does not have a heating element. So, its mechanism is a bit different from that of a typical pool heater. To put it simply, it is essentially the opposite of an air conditioner. To heat pool water, it uses sunlight and ambient air temperature. It does not produce as much heat as an electric or gas heater. A good thing about an electric pump is that it is cost-effective.

Solar pool heaters are the least powerful of all pool heaters, but they are the most cost-effective. To heat water, they utilize the rays of the sun. However, thermal solar heating is not the only technology that exists in the market. There are different technologies that use solar energy in different ways. There are more advanced technologies for solar water heating. But the installation costs are higher.

As a pool owner, you might ask the question: what size heater do I need for my pool? We have already tried to give you some hints. Below are the steps to calculate the exact BTU.

Step 1: Calculate the surface area of your pool

To determine the appropriate size of a pool heater, first of all, you have to calculate the surface area of your pool. There is a misconception among pool owners that a pool’s gallon size is used to determine its heater size. If you have a large pool, you are going to need a relatively large heater to heat the pool water. The calculation for finding out the surface area is pretty easy. Just multiply the length with the width.

Step 2: Divide the surface area by 3

To get the minimum BTU size, just divide the surface area of the pool by 3. For example, if the length is 30 and breadth is 15, the surface area will be 450. Divide it by 3 and you will get 150. Add 3 zeros to the number and you will get 150,000. So, the minimum BTU size for your pool is 150,000.

But bear in mind that it is the minimum size. In reality, you will need more BTUs than this. Oversizing the unit is actually a good idea when you are choosing a gas heater. However, an electric pool heater is also a good option. At the pool surface, the heat loss will be replenished by the pool heater.

The night is the time when heat loss usually happens. If there is no solar cover, it is impossible to compensate for the loss. A higher BTU size can be really helpful in such a case.

Step 3: Consider the variables

Before you make a decision, you have to take several variables into consideration. Climate, frequency of pool use, and solar cover are some variables that affect heater efficiency.

If you have a 15 by 30 pool and no solar cover, a 250K BTU model may be a good choice for you. With it, you can deal with evaporation, heat loss, and rough windy conditions. If you prefer to use the pool at night, it is good for you.

You can change the game by simply using a solar cover. A solar cover and a heater make a great combination for providing heat in a short span of time. A 250K heater is enough if you have a solar blanket. “What size heater do I need for my pool?” ask many pool owners. You already know that the answer depends on multiple factors.

Environmental Considerations

On the market, pool heaters that are available are usually environmentally friendly. Compared to earlier models, modern propane and gas heaters are highly efficient. However, gas or propane-fueled heaters are not as environmentally friendly as heat pumps. But if you are looking for the most environmentally friendly heater, you have to choose a solar pool heater.

However, you can not expect power and efficiency from the same heater. You will have to compromise either power or efficiency. The good news is, a gas heater can be paired with a solar heater. Maybe you are still asking the question: what size heater do I need for my pool? Well, a powerful heater is usually large in size. But you may not need a highly powerful one. Finding the right balance is key.


Choosing a pool heater is more than just calculating BTUs. And it is important to note that this calculation is not a flawless science. When you perform this calculation, you must consider natural heat loss. The most powerful pool heaters are powered by propane or natural gas. But if you take the environmental factors seriously, a solar heater can be a good choice for you.