Modern Hot Tubs: Efficiency Redefined

Modern Hot Tubs: Efficiency Redefined

Today, most consumers are very conscious of energy use—no matter the product. Therefore, it is important for manufacturers to consider the impact their products have on the environment. The trend to go ‘green’ is growing and has spawned several innovations as it pertains to product design and development. This method of thinking has also made its way into the hot tub industry. While most consumers know what a modern hot tub is, most still think they cost a lot of money to own and operate. In fact, the cost of operation is one of the most commonly asked questions by consumers shopping for a hot tub.

Early hot tubs might not have been the model of efficiency that modern designs are, but what appliances in the late ’70s were? In fact, most appliances were void of any energy guidelines until 1992 when the Energy Star program was initiated by the U.S. Environmental Protection Agency (EPA). This is a voluntary labelling program designed to identify and promote energy-efficient products to reduce greenhouse emissions. Computers and monitors were some of the first labelled products; however, the EPA eventually expanded the label to include office products, and residential heating and cooling equipment.

In 1996, the EPA partnered with the U.S. Department of Energy (DOE) and now the Energy Star label can be found on most major appliances, including office equipment, lighting, and electronics, in addition to new homes, and commercial and industrial buildings. The program’s overall goal is to give consumers a valid third-party endorsement, allowing them to shop and choose products that have the best energy savings.

In 2010, for instance, the program saved businesses, organizations, and consumers approximately $18 billion. More recently, Energy Star has been a driving force behind the more widespread use of technological innovations such as fluorescent lighting, power management systems for office equipment, and low standby energy use. The latter is what helped the hot tub industry create some of its consumer guidelines as well.

Early hot tub design did not focus on energy efficiency

Early hot tub designs were not that energy efficient. Product design was focused more on promoting relaxation and the product’s social aspects rather than energy efficiency. For example, some of the first wooden hot tubs were gas heated, prone to leaks, and void of any insulation.

With the onset of fibreglass and acrylic manufacturing processes, self-contained portable hot tubs became more efficient by default. Jumping ahead more than 35 years, today’s hot tubs are complex, insulated appliances that are built to stringent energy-use guidelines.

In contrast, it should also be noted, many consumers still want an inground plaster hot tub when they install a pool. These designs are beautiful and may look more integrated, but in the areas of energy efficiency, they cannot be compared to a self-contained hot tub. Plaster hot tubs take a long time to heat up and typically do not have an insulated cover. Once heated and used, the water is then mixed with the pool water volume, losing all of the heat. For a consumer who plans to use their hot tub on a regular basis, portable self-contained designs are far more cost effective to own and operate.

What makes today’s hot tub more efficient?

A key area that has helped hot tubs become more energy efficient is component design. While all hot tubs basically use the same components (e.g. hydraulic pumps, heaters, light-emitting diode [LED] lighting, insulation, and reinforcement systems, etc.), it is the combination of all these (or some) that help the modern hot tub attain an energy-efficient design.

While most hot tub manufacturers do not design their own components, they work closely with original equipment manufacturers (OEMs) that specialize in component design unique to the hot tub environment.

As energy efficiency is always top of mind for most consumers, OEMs have focused on new and improved designs for hot tub manufacturers to utilize in their designs to help lower energy consumption and cost of ownership.


Hydraulics is probably the most important feature inside a modern hot tub. The pump(s) is considered the ‘heart.’ When activated, it provides high flow water pressure to all of the jets. While there are some discrepancies in how manufacturers describe pump power, most rate them using brake horsepower (bhp), which is the measure of an engine’s horsepower before the loss in power caused by auxiliary components, e.g. water pump.

Another way to look at pumps is the amps (or energy) they use when running or starting. Modern pump designs have become very efficient with lower-amp usage and higher water flows. This allows manufacturers to use larger pumps while still keeping energy use to a minimum. In terms of jet pumps, most manufacturers are still using the larger jet pumps for cleaning and filtering; however, there are alternatives that can help consumers lower their operating costs further.Mag Drive Circ Pump_1

For instance, some higher-end manufactures are using small circulation pumps for water management systems instead of larger jet pumps. These pumps are integral to an energy-efficient design and help reduce overall operating costs. Small circulation pumps are called ‘mag’ drives because the impeller is floated using magnetic fields rather than mounted to a pump shaft. This shaft-less design not only makes them more energy efficient, but also reliable against leaks. They typically use only about 45 watts of energy and can be incorporated as part of a water management system that cleans the water 24-7 or drive the hot tub’s water features.

In addition, some pump manufacturers also make special ‘high-efficiency’ pumps. Despite the potential energy savings these high-efficiency motors offer, they use more copper than a typical motor, which makes them more expensive. The aforementioned magnetic-drive circulation pump is also an additional up front expense. However, a well-constructed hot tub should last 15 years; therefore, when considering the additional investment for energy efficiency over the long-term, it is not only good for the environment, but also the consumer’s pocketbook.


One of the main energy-consuming components of a hot tub is, of course, the heater. Modern electrical hot tub heaters are efficient and offer consumers a safe, reliable way to keep their hot tub ready for use at any time. While most manufacturers use a 5.5-kW heater, some use what is called ‘smart heat.’ These units comprise three heating elements (1.6, 4.0, and 5.5 kW) rather than one. This heater is especially advantageous when hot tubs are installed with less than a 50-amp circuit. The advantage of this is when the hot tub is being used and the water starts to cool off, the smart heat system will turn on a smaller element to provide heat recovery instead of not being able to heat at all due to insufficient power when pumps are running.


The brains of the hot tub have not been left out in the effort to make them more efficient and reliable. New controller and software designs allow consumers to custom program their hot tub to fit their lifestyle. For instance, the hot tub can be programmed to take advantage of ‘off-peak’ hours when running filter cycles so there is less of an impact on the overall household energy load.

In addition, some of the newer systems even make use of smartphone apps, which allow owners to adjust water temperature, filter cycles, and other programming features remotely. Many also adapt to different user profiles; for example, increased filtration on weekends when the hot tub is used more frequently and less filtration during the week when usage might be lower.

Other systems may have an ‘economy mode,’ which reduces the amount of time the pumps run to check the temperature. As hardware and software continue to evolve, the modern hot tub will soon be connected with ‘smart home’ technologies, which will communicate with all household appliances and balance energy loads according to needs and usage.


Another key component in portable hot tub design is the cover. Hot tub covers have several important tasks; the most important is safety. Simply put, the ability to lock the cover prevents unwanted entry to the hot tub.

Another important function they perform is insulating the hot tub against heat loss. When properly used, they can help maintain water temperature even in the coldest climates. A typical cover is approximately 76.2-mm (3-in.) thick and has a slight taper to help with water runoff. Most comprise expanded polystyrene (EPS) foam, the same material used in coolers to keep drinks cold.

The EPS, which has good insulating properties, is relatively lightweight and is covered in a 0.127- to 0.1778-mm (5- to 7-mil) sealed bag. EPS cores are made to fit inside marine-grade vinyl covers that are available in many colours and textures to match the hot tub’s exterior. They are also designed with a seam in the centre, which acts as a hinge, allowing users to easily open and close the cover.


Interior hot tub lights are not only a safety requirement, they also add to the esthetics of the hot tub design. Older models used incandescent bulbs with snap on colour lenses that created colours inside the hot tub. This was basically the same setup used in pools but on a smaller scale.

Modern hot tubs, however, take advantage of the latest in energy-efficient lighting technologies such as LED lighting. This relatively new technology is perfect for the hot tub industry as it can provide multi-colour lighting, light shows and low operating costs.

Further, LED lights also have a long lifespan and in most instances will last the life of the hot tub. They are one of the most popular features with consumers and manufacturers are responding to demand with new and innovative designs.

LED lights are being used on the hot tub’s exterior as well. They can serve as pathway or accent lighting for the hot tub itself. Many exterior lighting systems are designed to work with a photo cell that will turn the lights on at dusk and off at dawn. This is a common feature found in other architectural lighting products.

Water management

One area that has seen significant improvement in the last few years is water management. This not only applies to the technologies that help keep the water clean, but also the energy these systems use. For example, some new systems are using small magnetic drive circulation pumps to circulate and clean the water. These systems are far more efficient than using larger jet pumps to do the work.Water Care (2)

Not only are smaller pumps more efficient, but most of the heat created during their use is returned to the water. This helps keep the hot tub temperature stable, while also reducing the amount of time the heater has to operate. These newer, circulation pump-driven water management systems not only provide consumers with a cleaner, healthier hot tub, they also reduce maintenance costs.

New materials and design elements

Modern hot tubs achieve their overall efficiency using a combination of design elements, including:


Everyone understands the need for insulation; most homes built today have adequate insulation and meet the requirements and guidelines of California Energy Code (Title 24), The Energy Efficiency Standards for Residential and Non-residential Buildings. However, not thought about as often are the plethora of appliances consumers have in their home and the insulation systems they use.

From the wall-mounted oven or dishwasher to the side-by-side refrigerator, insulation either keeps the heat in or out. In fact, most people are surprised to learn that modern hot tubs use the same basic techniques and materials of a typical refrigerator.

Although many new insulation systems are now available to the hot tub industry—from urethane foam (used in high-efficiency refrigerators) to reflective foils (used in aerospace technology)—the goal is the same—keeping heat in the water. Energy efficiency comes at a price, however. Effective insulation systems cost more than minimal insulation, and a better insulated cover costs more than a thin cover. Therefore, it is better to pay for these efficiencies up front, rather than paying more down the road in higher operating costs.

Many hot tubs are sprayed with polyurethane foam, which fills any voids in and around the plumbing (i.e. full foam). The foam is available in a variety of densities as it not only insulates the plumbing and hot tub shell, but also doubles as structural support for the flex tubing used in most plumbing designs. This is the most widely used system in the industry as it has the best performance history.

Another insulation technique involves using a rigid sheet of polyurethane foam comprising a reflective surface to capture the warm air on the inside of the hot tub. This helps prevent heat loss by creating a barrier to capture heat from the pump and keep it in the area created by the rigid foam panel and back of the hot tub shell. One advantage of these systems is the plumbing remains exposed for easy accessibility.

Some manufacturers also use standard batted fibreglass insulation in and around equipment areas to help protect the plumbing from freezing. This insulation, commonly found in the walls of most homes, is effective as well as easy to use and replace if it becomes damaged.

Reinforcement systems

One area not so apparent to consumers, but still important, is the reinforcement system. This is what gives the hot tub shell its strength. While fibreglass is still popular, there are new materials that are more environmentally friendly. For example, many manufacturers are now using new high-density polyurethane materials for shell reinforcement. This material does not contain any volatile organic compounds (VOCs) and is much safer for the manufacturing environment.

It can also be applied using automation processes (e.g. robots) instead of physical labour. The one downfall of this material, however, is its cost as it is more expensive than fibreglass.

Green manufacturing processes

In today’s hot tub manufacturing environment, many improvements have come through the experience of other industries. For instance, the automobile manufacturing industry has proven the effectiveness of programs such as Lean, Just In Time (JIT), Kaizen (Japanese for ‘improvement’ or ‘change for the better’), and the International Organization for Standardization (ISO).

Many hot tub manufacturers are adopting these new techniques as ways to improve product work flow, manage inventory, and improve product quality. These programs are also important in reducing manufacturing waste.

Continuous improvement programs can deliver green manufacturing results through the very essence of Lean, which is waste reduction. In a quest to reduce operational waste on all fronts, the byproduct has always been reduced environmental waste. In fact, in the last few years, many companies have reduced manufacturing cycle times, process variability, and inefficiencies in all areas.

To achieve these lean results, manufacturers have had to reduce non-value added process steps diligently, and as a consequence, non-value added parts and raw materials, all of which have a direct impact on the environment, have also been decreased. For example, most companies have reduced epoxy usage by 70 per cent, chemical VOCs by 40 per cent and parts usage (e.g. fittings and hoses) by 25 per cent. Further, the energy required during the manufacturing process has also decreased via the efficiencies gained.

Recycled materials

This area is quite new to the hot tub industry as there are not many components that can use recycled material. However, some manufacturers are exploring the use of recycled denim (cotton) as an insulation material, as well as some new engineered cellulose materials made from recycled paper. New fibreglass material designs are now also using post-consumer content, which further helps with the green footprint.

Further, materials like polystyrene used in hot tub cover construction, can also be recycled and is growing in popularity. The movement towards more sustainable materials will continue to grow and give manufacturers more options when designing energy-efficient hot tubs to reduce operating expenses.

Understanding Energy Consumption
To raise the temperature in a hot tub containing 1,552 L (410 gal) of water by one degree it takes 1 kilowatt hour (kWh) of electricity.
Therefore, a 1-kW heater will take one hour to raise the temperature, while a 4-kW heater will accomplish this task in 15 minutes. A larger heater does not use more energy to heat the water, it just heats it faster.
Higher voltage does not mean more energy use, either. Watts (W) or kilowatts (kW) equals voltage times amperage. For example, a 1-kW heater at 110 V uses 9 amps, whereas a 1-kW heater at 220 V uses 4.5 amps. Therefore, both 110- and 220-V heaters use the same amount of electricity to heat the water.


Hot tubs have changed considerably over the years and are not the ‘energy hogs’ everyone thinks they are. The benefits of hot tub ownership, which provide wellness for the body, mind, and spirit, are well worth the cost of a modern hot tub.

The more the consumer knows about the product they are buying, the better they will understand the impact it will have on their household energy bill.

This article was written by Vic Walker and originally appeared on Pool & Spa Marketing [link].