Spa Heater Sizing Guide

Which Spa Heater is Best?

Pool season might be over, but hot tub season is just beginning. Few things are as soothing as slipping into a warm, bubbling spa after a long day. But one of the frustrations of having a standalone hot tub or built-in spa area with an inground pool is how long it takes to get it to temperature. Picking the spa heater size for your hot tub is simpler than you might think.

In this article, we’ll show you how to pick the correct spa heater for your application and help you determine what type is best for you.

Electric Spa Heaters

Electric element heaters are the most common type of spa and hot tub heating used in America. The electric heater’s compact size means it can fit into most equipment pads. But when heating your water, these super compact units punch well above their weight.

Electric Heater Advantages

  • Compact
  • No gas required

Electric Heater Disadvantages

  • Operational costs – Electricity is not cheap; electric heaters burn through it as quickly as they can get it.
  • Modifications to your breaker box and/or circuitry will be required for larger heater kW output.

Recommended Models

Spa Size in Gallons5.5kW11kW18kW27kW
300NormalNormalRapidRapid
400SlowNormalRapidRapid
500SlowNormalNormalRapid
600Not RecommendedSlowNormalRapid
700Not RecommendedSlowNormalRapid
800Not RecommendedSlowSlowNormal
900Not RecommendedSlowSlowNormal
1,000Not RecommendedNot RecommendedSlowNormal
1,200Not RecommendedNot RecommendedNot RecommendedNormal
1,400Not RecommendedNot RecommendedNot RecommendedSlow
1,600Not RecommendedNot RecommendedNot RecommendedSlow
1,800Not RecommendedNot RecommendedNot RecommendedNot Recommended
2,000Not RecommendedNot RecommendedNot RecommendedNot Recommended
Slow – 0° to 10° Fahrenheit Rise Per Hour
Normal – 11° – 25° Fahrenheit Rise Per Hour
Rapid – 26° – 50° Fahrenheit Rise Per Hour

Above Ground Pool Gas Pool Heaters

If you’re in an area where Natural Gas or Liquid Petroleum (propane) is cheaper than electricity, an above-ground pool heater might be the best choice

Advantages

  • Higher BTU output than electric heaters
  • Heats quicker
  • Great for larger spas or small wading pools
  • More compact than inground pool heaters

Disadvantages

  • Requires Gas: natural gas heaters must be plumbed into local gas lines, and propane heaters require a large propane tank.
  • Above ground pool heaters are more expensive than most electric heaters.

Recommended Models

Spa Size in Gallons106,000 BTU125,000 BTU156,000 BTU
400RapidRapidRapid
500RapidRapidRapid
600NormalRapidRapid
700NormalRapidRapid
800NormalNormalRapid
900NormalNormalNormal
1,000NormalNormalNormal
1,200SlowNormalNormal
1,400SlowNormalNormal
1,600SlowSlowNormal
1,800SlowSlowSlow
2,000SlowSlowSlow
Slow – 0° to 10° Fahrenheit Rise Per Hour
Normal – 11° – 25° Fahrenheit Rise Per Hour
Rapid – 26° – 50° Fahrenheit Rise Per Hour

Inground Pool Heaters

By far the quickest spa heating option, inground pool heaters are best for owners of large party spas or those who want to heat their pool.

Advantages

  • Immediate Heat: gets the water to the desired temperature the fastest
  • Great for heating your whole pool as well as the spa

Disadvantages

  • More expensive option
  • Requires larger natural gas lines or propane tank
  • Overkill for most spa sizes
  • Should only be used on inground / spas

Recommended Models

Spa Size in Gallons250,000 BTU330,000 BTU400,000 BTU
400RapidRapidRapid
500RapidRapidRapid
600RapidRapidRapid
700RapidRapidRapid
800RapidRapidRapid
900RapidRapidRapid
1000RapidRapidRapid
1,200NormalRapidRapid
1,400NormalRapidRapid
1,600NormalRapidRapid
1,800NormalNormalRapid
2,000SlowNormalRapid
2,200SlowNormalNormal
2,400SlowSlowNormal
2,600SlowSlowNormal
Slow – 0° to 10° Fahrenheit Rise Per Hour
Normal – 11° – 25° Fahrenheit Rise Per Hour
Rapid – 26° – 50° Fahrenheit Rise Per Hour

Still have some spa heater questions? Leave a comment down below or speak to one of our tech over at INYOPools.com.

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