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

Raypak E3T Digital Heaters – 18kW & 27 kW Options Available
HydroQuip HeatMax RHS Heaters

Spa Size in Gallons	5.5kW	11kW	18kW	27kW
300	Normal	Normal	Rapid	Rapid
400	Slow	Normal	Rapid	Rapid
500	Slow	Normal	Normal	Rapid
600	Not Recommended	Slow	Normal	Rapid
700	Not Recommended	Slow	Normal	Rapid
800	Not Recommended	Slow	Slow	Normal
900	Not Recommended	Slow	Slow	Normal
1,000	Not Recommended	Not Recommended	Slow	Normal
1,200	Not Recommended	Not Recommended	Not Recommended	Normal
1,400	Not Recommended	Not Recommended	Not Recommended	Slow
1,600	Not Recommended	Not Recommended	Not Recommended	Slow
1,800	Not Recommended	Not Recommended	Not Recommended	Not Recommended
2,000	Not Recommended	Not Recommended	Not Recommended	Not 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 Gallons	106,000 BTU	125,000 BTU	156,000 BTU
400	Rapid	Rapid	Rapid
500	Rapid	Rapid	Rapid
600	Normal	Rapid	Rapid
700	Normal	Rapid	Rapid
800	Normal	Normal	Rapid
900	Normal	Normal	Normal
1,000	Normal	Normal	Normal
1,200	Slow	Normal	Normal
1,400	Slow	Normal	Normal
1,600	Slow	Slow	Normal
1,800	Slow	Slow	Slow
2,000	Slow	Slow	Slow

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

Hayward Universal H-Series Low Nox Pool heater — **Hayward Universal H-Series Heater, Low NOx**

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 Gallons	250,000 BTU	330,000 BTU	400,000 BTU
400	Rapid	Rapid	Rapid
500	Rapid	Rapid	Rapid
600	Rapid	Rapid	Rapid
700	Rapid	Rapid	Rapid
800	Rapid	Rapid	Rapid
900	Rapid	Rapid	Rapid
1000	Rapid	Rapid	Rapid
1,200	Normal	Rapid	Rapid
1,400	Normal	Rapid	Rapid
1,600	Normal	Rapid	Rapid
1,800	Normal	Normal	Rapid
2,000	Slow	Normal	Rapid
2,200	Slow	Normal	Normal
2,400	Slow	Slow	Normal
2,600	Slow	Slow	Normal