Pools
Pool heater installation cost
Sizing a pool heater is two questions and almost nobody separates them. Holding 82°F against 60°F air is a problem of surface — 56,320 BTU an hour here, with the volume playing no part at all. Reaching it, 10°F in 12 hours, is a problem of volume: 190,080. And then the item nobody checks — the ¾ in gas line most houses have carries 110,532 BTU an hour at 60 feet, against the 250,000 the heater asks for.
Written and edited by Pablo Ruiz Quintero
Last reviewed 2026-09-23 · Nothing you type leaves your browser
Pool heater installation calculator
Two questions, two answers
Holding a temperature is a problem of surface area. Reaching one by Saturday is a problem of volume. Heaters are sold in BTU and serve both badly if nobody says which.
Inside the walls.
Inside the walls.
Length times width, and nothing to argue about. Most inground pools and every lap pool.
Gunite and concrete pools
It changes the gallons and therefore how long a heat-up takes. It does not change the heat loss at all.
Holding a temperature
A surface problem. Only the water’s area, the air and the cover matter.
Every degree costs the same to hold, so 82 is meaningfully cheaper than 86 and most people cannot tell.
Not the summer average — the shoulder-season night that made you want a heater in the first place.
The largest single lever on this page, and it is the cheapest thing on it.
Reaching a temperature
A volume problem. This is what usually sizes the heater, and it is the question nobody is asked.
From where the pool sits on its own to where you want it.
Overnight is about 12 hours. A heat pump generally cannot do it in that, and that is the real difference between the two machines.
The machine and the supply
Fast, available on demand and expensive per degree. It does not care what the weather is doing, which is the entire argument for it: a gas heater warms a pool for a weekend in April, and nothing else does.
What most houses run to an appliance, and what the run to a pool pad usually is if there is one at all. At any real distance it carries about a quarter of what a pool heater asks for.
Capacity falls with length, so a short fat run and a long thin one are different animals. Pace it out.
Replacing an existing heater, so the pad and the tie-ins are there.
Used only to pick a regional labour rate. It stays in your browser.
Gas heater · 250,000 BTU/hr
$4,955
holding 56,320 · reaching 190,080 · 10.4 h to warm up
Reaching the temperature is what sizes this
Holding 82°F against 60°F air needs 56,320 BTU an hour — a function of 512 ft² of water surface, with the volume playing no part. Raising it 10°F in 12 hours needs 190,080, which is entirely about the 19,246 gallons. They differ by 3.4 times.
The gas line will not feed it
110,532 available, 250,000 asked for
A ¾ in line over 60 ft carries about 110,532 BTU an hour. It is not marginal — it is roughly a third of what this heater wants. The smallest line that works at this distance is 1¼ in.
That is a trench back towards the meter and about $1,840 of work — the item that turns a heater swap into a week, and the one nobody has thought about when they ask what a heater costs. It is checkable in two minutes by reading the pipe.
Four machines, same pool
What each one costs to put in, and how long it takes to warm the water.
| Heater | Fitted | Warm-up | Supply work |
|---|---|---|---|
| Gas heater · yours | $4,955 | 10.4 h | Needs the gas line upsized. |
| Heat pump | $7,740 | 19.2 h | Needs a 240 V circuit. |
| Electric resistance | $2,357 | — | Needs a 240 V circuit. |
| Solar collectors | $6,640 | — | No running cost and no control over when it happens. |
Surface, volume, and what the pipe will carry
All in BTU an hour, on the same scale.
What the job is made of
- Gas heater, 250,000 BTU/hr
Fast, available on demand and expensive per degree. It does not care what the weather is doing, which is the entire argument for it: a gas heater warms a pool for a weekend in April, and nothing else does.$2,125 - Fitting, in place of the old one
Pad, unions, gas or electrical connection and commissioning, where everything is already where it needs to be.$780 - Upsizing the gas line to 1¼ in
The ¾ in line carries 110,532 BTU an hour over 60 ft and this heater asks for 250,000. Priced by the foot back towards the meter, and the meter itself may need looking at.$1,840 - Permit and inspection
Gas work and a new circuit both want signing off, and a pool heater is exactly the kind of thing a surveyor asks about later.$210
What it costs
National average. Gas heater, 250,000 BTU/hr, replacing an existing unit, with the gas line upsized to 1¼ in. Not included: a cover, the pump or filter, and any concrete work at the pad.
What it then costs to run — which on a heated pool is larger than everything else on the property put together — is a different bill entirely. The gallons and the surface area both come from the shape of the pool, and the cover that halves the heating is the cheapest thing on either page.
Worth knowing
- Sizing a heater is two questions with different answers. Holding 82°F against 60°F air is a problem of surface — this pool loses about 56,320 BTU an hour through 512 ft² of water, and the volume never enters it. Reaching it, 10°F in 12 hours, is a problem of volume: 190,080 BTU an hour. The second is what is sizing this heater.
- The ¾ in gas line will not feed this. Over 60 ft it carries about 110,532 BTU an hour and the heater asks for 250,000 — it is not close, it is a third. The smallest line that works at this distance is 1¼ in, which means a trench back towards the meter and about $1,840 of work. This is the item that turns a heater swap into a week, and it is checkable in two minutes by reading the pipe.
- A 250,000 BTU gas heater raises this pool 10°F in about 10.4 hours against the 12 asked for, because the smallest catalogue model above the requirement overshoots it. That losing half is 56,320 BTU an hour and it never stops.
- No cover. The loss this heater is fighting is 56,320 BTU an hour and a cover would take it to about 16,896 — a 70 per cent cut, because most of what a pool loses goes out as evaporation and a cover stops evaporation. It is the largest single lever on this page and it costs a few hundred dollars once.
- Heaters are sold by their input and the pool only ever sees the output. A 250,000 BTU gas heater at 84 per cent puts 210,000 into the water. Compare models on the same side of that.
On this page — 4 sections
Two questions with different answers
The short version
- Holding a temperature is surface. 56,320 BTU/hr here, and the volume plays no part.
- Reaching one is volume. 190,080 BTU/hr — 3.4 times as much.
- A ¾ in gas line carries 110,532 at 60 ft. The heater asks for 250,000.
- A cover cuts the load 70 per cent — more than the choice of machine does.
Ask what size pool heater you need and you will get one number. There are two, they are answers to different questions, and they are nowhere near each other.
Holding a pool at a temperature is a problem of surface area. A pool loses its heat through the water’s surface — and about seventy per cent of that loss is evaporation, which is why a cover does so much. The volume of the pool does not appear in the calculation anywhere. A deep pool and a shallow one of the same shape lose heat at exactly the same rate.
Reaching a temperature by Saturday is a problem of volume. Now every gallon has to be lifted by every degree, and the surface only matters because the pool keeps losing heat while it gains.
On this pool those are 56,320 and 190,080 BTU an hour. Almost everything published answers the second and quietly sells the first.
| Water surface | 512 ft² | What holding costs depends on |
| Volume | 19,246 gal | What reaching costs depends on |
| Holding 82°F against 60°F | 56,320 BTU/hr | Surface × difference × 5 |
| Raising 10°F in 12 h | 190,080 BTU/hr | Gallons × 8.34 × degrees, plus the loss |
| The model that follows | 250,000 BTU/hr | Smallest catalogue size above the requirement |
The two loads differ by 3.4 times, and which one you are solving decides both the size of the machine and which kind of machine it should be.
US Department of Energy, and ASHRAE, Swimming pool heat loss and heater sizing · checked 2026-09-23
The line already in the ground
Here is the item that turns a morning into a week, and it costs nothing to check: the gas pipe at the pad.
A gas line’s capacity depends on its diameter and its length, and it falls off faster with distance than people expect. The ¾ inch line that most houses run to an appliance carries about 110,532 BTU an hour over 60 feet.
A full-output gas pool heater asks for 400,000.
That is not marginal and it is not a matter of a slightly lower flame. It is roughly a quarter of what the appliance needs, and the answer is a larger pipe run back towards the meter — priced by the foot, through whatever is between the pad and the house.
| Pipe | 20 ft | 40 ft | 60 ft | 80 ft | 100 ft |
|---|---|---|---|---|---|
| ½ in | 95k | 66k | 54k | 46k | 41k |
| ¾ in | 196k | 136k | 111k | 95k | 85k |
| 1 in | 361k | 251k | 204k | 175k | 156k |
| 1¼ in | 752k | 524k | 425k | 366k | 326k |
| 1½ in | 1133k | 790k | 640k | 551k | 491k |
BTU an hour of natural gas. The darker figures are the ones that will feed a 400,000 BTU heater — and there are not many of them. Read the size off the pipe and pace out the run.
National Fire Protection Association, NFPA 54, National Fuel Gas Code — pipe sizing tables · checked 2026-09-16
Gas or heat pump is a question about time
The comparison is usually framed as efficiency, and framed that way the heat pump wins so heavily that the question looks settled. It is the wrong frame.
A heat pump moves heat rather than making it, so it delivers about five and a half units for every one it consumes. It also works slowly, and it stops working properly when the air drops below about 50°F — which is precisely the weather that makes somebody want a heater.
So the real question is when you want the pool warm. Continuously through a season, or by Saturday.
| Gas heater | Heat pump | |
|---|---|---|
| Fitted | $4,955 | $7,740 |
| Raising 10°F | 10.4 hours | 19.2 hours |
| In 45°F air | Unaffected | Barely works |
| Running cost | High, per degree | About a fifth of that |
| Supply work | Usually a bigger gas line | A 240 V circuit |
| Best at | Warm by the weekend | Warm all season |
Before choosing between them
- Decide honestly whether the pool gets used on a plan or on a whim. A heat pump serves a plan and cannot serve a whim.
- Look up the overnight temperatures in the months you actually want to swim, not the summer averages.
- Read the gas pipe at the pad and pace the run to the meter. It may settle the question on its own.
- Check what is in the electrical panel. A heat pump wants its own circuit and its own breaker.
- Price a cover in both cases, because it changes the size of either machine.
- Ask about noise if the pad is near a neighbour — a heat pump runs for hours and a gas heater runs briefly.
- Consider solar as a second heater rather than an only one. Its running cost is nil and its control is nil with it.
- Work out the running cost before the capital cost. On a heated pool it is the larger number by a distance.
$4,955
Gas, with the line upsized
$3,115 where it is already adequate
$7,740
Heat pump, fitted
19.2 h to raise 10°F
110,532
What a ¾ in line carries
BTU/hr at 60 ft
70%
What a cover saves
Of the holding load, every hour
MaterialsEstimator, Pool heater price survey — units, gas work and electrical · checked 2026-09-23
What goes wrong
01Sizing on one number
Holding and reaching are different problems with different answers — 56,320 and 190,080 BTU an hour here, 3.4 times apart.
Instead — Say which you are solving. A heater sized to hold a temperature will never reach one in a weekend, and one sized to reach one is enormous for holding.
02Not reading the gas pipe before buying
A ¾ in line carries 110,532 BTU an hour at 60 ft and a full-output heater asks for 400,000. It is a quarter, not a near miss.
Instead — Read the size off the pipe and pace the run. It takes two minutes and it is the difference between a morning and $1,840 of trench.
03Buying a heat pump to use in spring
It moves heat out of the air, and below about 50°F there is not enough in it to move. Output falls away and then stops, in exactly the weather that prompted the purchase.
Instead — Check the overnight temperatures for the months you actually want to swim. If they are cool, the answer is gas or it is a cover and patience.
04Treating the cover as an accessory
It cuts the holding load by 70 per cent — from 56,320 to 16,896 BTU an hour — because evaporation is most of the loss.
Instead — Budget it with the heater. It changes the size of machine you need, not just what it costs to run.
05Comparing input ratings with output ratings
A gas heater is sold by the gas it burns; a heat pump is sold by the heat it delivers while consuming a fifth of that. Comparing the two numbers directly compares nothing.
Instead — Convert everything to output — what actually reaches the water — and compare there.
06Sizing electric resistance for a pool
The largest domestic unit is about 15 kW and this pool asks for 190,080 BTU an hour — around 56 kW, or 232 amps. That is a new service, not an appliance.
Instead — Use resistance on a spa or a plunge pool. On a full-sized pool it is either gas, a heat pump or the sun.
07Assuming the meter is fine because the branch is
A pool heater is often the largest appliance on a domestic gas supply. Upsizing the branch does not help if the meter cannot pass the whole house's demand at once.
Instead — Ring the utility before digging. It is usually free and it is the one call that can invalidate the whole plan.
08Buying the heater before working out the running cost
On a heated pool, running it costs more than everything else on the property put together, and the capital cost is the smaller decision.
Instead — Work out the annual cost first, with and without a cover, and let that decide whether to heat at all.
- 01Decide which question you are askingHolding a temperature all season, or reaching one by the weekend. They have different answers and different machines.
- 02Work out the holding loadSurface area times the difference between water and air, times about 5. The volume plays no part in it.
- 03Work out the heat-up loadGallons times 8.34 times the degrees, divided by the hours you will accept — plus the holding load, because the pool keeps losing heat while it gains.
- 04Take the larger of the twoThat is the output the heater has to deliver. Divide by its efficiency to get the input it is sold as.
- 05Read the gas pipe at the padThe size is printed on it. This is the step nobody takes and it is the one that decides whether the job is a morning or a week.
- 06Check that pipe against the heaterCapacity falls with length. A ¾ in line at any real distance carries about a quarter of what a full-output gas heater asks for.
- 07Price a cover in the same conversationIt cuts the load by about 70 per cent, which changes the heater you need as well as what it costs to run.
Fitting the heater is the smaller half. Heating is not another line on a pool’s running costs — it is a larger bill than everything else combined, and whether it is affordable at all is decided by the cover rather than by the machine.
And then what it costs to run- BTU per hour
- The rate a heater delivers heat. It is the unit heaters are sold in, and it answers two different sizing questions badly unless you say which one you are asking.
- Input and output
- A gas heater is rated by the gas it burns and the pool only feels what comes out the other side. At 84 per cent efficiency a 400,000 BTU heater delivers about 336,000, and a heat pump inverts the relationship entirely.
- Coefficient of performance
- How many units of heat a heat pump moves per unit of electricity it uses — around five and a half on a pool unit. It is why a heat pump costs a fifth of electric resistance to run.
- Surface loss
- How a pool loses heat: through the water's surface, about 5 BTU an hour per square foot for each degree between the water and the air. Evaporation is most of it, which is why a cover matters so much.
- Heat-up
- Raising the pool from where it sits to where you want it. It is the volume question, it is what usually sizes the heater, and nobody is asked about it in a showroom.
- Gas line capacity
- How much a pipe can carry, which falls with length. A ¾ in line carries about 110,532 BTU an hour at 60 ft and a 1¼ in line about 424,675.
- Meter
- The gas meter serving the house. A branch being adequate does not mean the supply is: adding a pool heater can exceed what the meter is rated to pass for everything at once.
- Bypass
- Valves that let water go round the heater rather than through it. It is how a heater is isolated for service and how flow is trimmed to what it wants.
- Shoulder season
- Spring and autumn, when the air is cool and the pool is not. It is when people decide they want a heater, and it is exactly when a heat pump is at its weakest.
- Solar collectors
- Panels the pool water is pumped through. No running cost and no control — it heats when the sun is out, by whatever the sun decides.
- Electric resistance
- A heating element in the water path. Every unit of electricity becomes one unit of heat, against five and a half for a heat pump, and the largest domestic unit is about 15 kW — a spa machine rather than a pool one.
- Cover
- A solar or safety cover. It cuts the surface loss by about 70 per cent, which makes it the largest single lever on both the size of the heater and the cost of running it.
Common questions
- How much does it cost to install a pool heater?
- About $3,115 for a gas heater where the supply is already adequate, and $4,955 where the gas line has to be upsized — which on a ¾ in run of 60 ft it does. A heat pump is around $7,740 including a dedicated 240 volt circuit. The unit itself is often the smaller half of that.
- What size pool heater do I need?
- It depends which question you are asking, and they have very different answers. Holding 82°F against 60°F air on this pool needs 56,320 BTU an hour — that is a function of the 512 ft² of water surface and the volume never enters it. Raising the pool 10°F in 12 hours needs 190,080, which is entirely about the 19,246 gallons. They are 3.4 times apart.
- Can my gas line handle a pool heater?
- Probably not, and it is the cheapest thing on this page to check. A ¾ in line — which is what most houses run to an appliance — carries about 110,532 BTU an hour over 60 ft. A full-output gas pool heater asks for 400,000. You need 1¼ in at that distance, and going from one to the other is a trench back towards the meter: about $1,840 of work. The pipe size is printed along the pipe.
- Gas heater or heat pump?
- It is a question about when you want the pool warm, not about efficiency. A gas heater raises this pool 10°F in about 10.4 hours and does not care what the weather is doing. A heat pump takes about 19.2 hours and stops working properly below about 50°F of air. Gas is for a pool you want warm by Saturday; a heat pump is for a pool you keep warm all season, and it runs for a fifth of the money once it is there.
- Why doesn't a heat pump work in cold weather?
- Because it does not make heat, it moves it — out of the air and into the water. Below about 50°F there is progressively less to move and the output falls away, then stops. Which is unfortunate, because cool air is exactly the condition in which somebody decides the pool needs heating. If the pool is wanted warm in spring and autumn rather than through the summer, no amount of oversizing fixes it.
- Is electric resistance heating an option?
- Not for a full-sized pool. The largest unit anybody fits to a house is about 15 kW — 51,000 BTU an hour, already 62 amps at 240 volts — and this pool asks for 190,080. Sizing one to that would be about 56 kW and 232 amps, which is not an appliance but a new service. It is a spa and plunge-pool machine.
- How much difference does a cover make?
- More than the heater choice does. It cuts the holding load from 56,320 BTU an hour to about 16,896 — 70 per cent — because most of what a pool loses goes out as evaporation and a cover stops evaporation. It changes the size of heater you need as well as what it costs to run, and it costs a few hundred dollars once.
- How long does a pool heater take to warm the pool?
- This pool, 10°F: about 10.4 hours on the gas heater and 19.2 on the heat pump. The gap is the whole difference between the two machines. And both are fighting the 56,320 BTU an hour the pool is losing the entire time — which is why a cover shortens a heat-up as well as cheapening it.
- Do I need a permit?
- Usually, for both. Gas work and a new 240 volt circuit are both notifiable nearly everywhere, and a pool heater is exactly the kind of appliance a surveyor asks about when the house changes hands. It is a small cost against redoing gas work retrospectively.
- What does a pool heater cost to run?
- Far more than it costs to fit, and that is the thing to settle before buying one. Heating is not another line on a pool's running costs — it is a larger bill than everything else on the property put together, and whether it is affordable at all is decided by the cover rather than by the heater.
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About the author
Pablo Ruiz Quintero — Editor
Editor of MaterialsEstimator. Decides which documents count as a source, what every default value is, and where the line sits between what the reader parses and what the engines compute.
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