Pentair MasterTemp 400: Does it Cost Too Much To Run?

Preface- The Pentair Mastertemp 400 is great for large pools, night time dips and chillier climes. No one likes paying for repeat gas so thankfully this heater is highly efficient, more so than smaller units. It’s also easy to operate and reliable. But does it cost too much to run?

Pentair pool heater best features


If you have been searching through all the pool heater reviews on Google trying to find a low cost solution for heating your pool, then you’ve come to the right place.

What’s the point in having a beautiful pool that you can’t make use of because you risk hypothermia just dipping your toe in it? Unless, it’s just a picturesque show-off garden feature.

After price 2 things are crucial, the time it takes to work, and the running costs. This review answers exactly that.

If you have a large pool and aren’t fortunate enough to live in one of the hotter locales like The OC, Florida or Arizona, then gas pool heaters work best. Heat pumps are quite sore on electricity and they need a lot of warm air to transfer through to your pool. So in colder states gas is the best way to go. Solar is just too ineffective.

This article introduces you to the Pentair MasterTemp 400 one of the most powerful and highly efficient natural gas heaters currently on the market.


What We like

  • Works EXTREMELY fast
  • Small, compact heater
  • Eco-friendly - Low NOX emissions
  • Award winning energy efficiency
  • Not too difficult to install
  • Durable rust proof exterior
  • Rotating top dial pad to suit your plumbing (to face either left or right)
  • Simple set and forget heating controls via digital dialpad
  • Auto shut off to prevent overheating
  • Vast array of safety features and sensors including manual gas shut off for services
  • Comprehensive clear to understand manual
  • 3 year warranty (once product is registered)
  • Suitable for saltwater pools + all pool types, bromine, hard water, high flow pressure
  • Natural gas or propane models


In a hurry? Check out the latest deals & discounts from our top online suppliers for this powerful heater. If you buy from sites like Amazon and don't have the heater professionally installed you will void the 3 year warranty. That's why it's better to buy from an official pool supply company.




Here are some average prices to compare against. If you live in Phoenix Az you want your water temp to consistently stay at 78º  can expect to pay approx $1384 in gas costs for the entire swimming season. _ but here's the biggie- if you use a pool cover you can end up paying a meagre $96. ASTONISHING. If you want the water 82º  you'll pay $256- SO LONG AS YOU USE A COVER.


Location Season Temperature
78° 80° 82°
Miami 1/1–12/31 $2136 $2848 $3600
w/cover 1/1–12/31 $416 $584 $800
Phoenix 3/1–10/31 $1384 $1776 $2216
w/ cover 3/1–10/31 $96 $168 $256
Dallas 4/1–10/31 $1512 $1920 $2456
w/ cover 4/1–10/31 $184 $280 $408
Atlanta 4/1–10/31 $1704 $2248 $2880
w/ cover 4/1–10/31 $320 $424 $592
Los Angeles 5/1–10/31 $1864 $2376 $2904
w/ cover 5/1–10/31 $168 $304 $472
Kansas City 5/1–10/31 $1434 $1872 $2384
w/ cover 5/1–10/31 $288 $416 $544
New York 5/1–9/30 $1448 $1904 $2384
w/ cover 5/1–9/30 $208 $296 $400
Chicago 5/1–9/30 $1621 $2072 $2536
w/ cover 5/1–9/30 $216 $296 $384
Denver 5/1–8/31 $1757 $2120 $2498
w/ cover 5/1–8/31 $123 $168 $243
Boston 5/1–8/31 $1712 $2096 $2504
w/ cover 5/1–8/31 $232 $328 $461
Minneapolis 6/1–9/30 $1331 $1776 $2176
w/ cover 6/1–9/30 $192 $248 $384
San Francisco 6/1–8/31 $1560 $1856 $2168
w/ cover 6/1–8/31 $192 $320 $472
Seattle 6/1–8/31 $1525 $1784 $2056
w/ cover 6/1–8/31 $304 $424 $552

*Figures based on a 1,000 square-foot, outdoor pool heated with an 80% efficient natural gas heater at $.80 per therm and uncovered for 8 hours per day.

If you're replacing a gas pool heater, you can use the following formula to determine your annual cost savings with a higher efficiency gas pool heater model:

Current Annual Cost x [1 – (Current Efficiency ÷ New Efficiency)]


Other Factors Influencing Running Costs

Different States naturally have different running costs as the cost of natural gas for instance and the climate varies. It will take less gas to heat up your pool on sunny days where the ambient air and humidity is higher. It also depends on high you like the temperature of your pool to be, and whether you leave a pool cover on in between swimming times.

One thing is clear though this is a highly efficient heater and you will wait less time for it to heat up large pools due to the 400 000 btu, and that goes without saying for hot tubs and smaller pools under 20,000 gallons.

If your climate is a bit too northern for your liking you can certainly extend your swimming season for up to 8 more weeks with a powerful gas heater.

A single BTU (British Thermal Unit) can raise the temperature of 1lb of water by 1 degree which means that the more BTUs a pool heater can produce, the quicker the water will heat up in your swimming pool.