By Azur Dzindo
Energy efficiency; consumers demand it and product development teams strive for it. These days, it is also the focus of advertising and packaging designs for nearly all home and industrial equipment. From light bulbs to dishwashers to automobiles, the amount of energy consumed is a major factor in the research and development (R&D) of new products, not to mention their ultimate purchase by the end-user.
Pool heaters are no exception. In fact, the various types of pool heaters on the market are often compared to each other based on energy efficiency. The four available heating technologies in the pool industry are: gas (natural gas or propane), heat pump, electric resistance-style (very few pools use these systems anymore), and solar. It is generally understood that heat pump technology is more energy efficient than gas, while electric resistance-style heaters are less efficient. Solar heating is the most efficient in terms of the cost of generating heat (it is free from the sun), but there are variables in how efficiently water is pumped from the heat source (e.g. roof-mounted panels) to the pool, as well as in the cost of the solar collectors.
That being said, this article will focus on gas heaters as they are the most commonly used for pools and have changed the most over the past 30 years.
Early product efficiencies
Energy efficiency has been a primary comparison point for gas pool heaters since the ’80s with the introduction of millivolt electronic ignition. This technology provided noticeable energy savings over pilot igniters.
Gas heaters have historically been categorized by their thermal efficiency rating. Units that can achieve thermal efficiency ratings above 90 per cent are considered high-efficiency heaters. The thermal efficiency of gas heaters is a measure of how much of the heat generated by the consumed gas is actually transferred to the water (as heat). That is, if a heater consumes 400,000 British Thermal Units per hour (BTUs/hr) of gas and uses 336,000 BTUs/hr to heat the water (because the other 64,000 goes to exhaust, by design), that heater will have a thermal efficiency rating of 84 per cent (336,000 is 84 per cent of 400,000). This is the typical range for most gas pool heaters today.
By using high-efficiency condensing technology, some pool heaters have been able to achieve thermal efficiency ratings above 90 per cent. That is, the heater is able to use 92 to 95 per cent of the heat energy generated by the gas it consumes to heat the water, while very little energy goes to waste. (The energy that does not go into heating the water is released into the atmosphere as exhaust. The first pool heater to use condensing technology and offer this level of thermal efficiency was the ‘Hi-E,’ brought to market in the ’90s by the company then known as Teledyne Laars.
Internal heater challenges
One of the biggest challenges of pool heater design—no matter the efficiency rating—is the harsh internal environment. This is a result of two factors: condensation and pool chemicals.
Condensation that forms inside any pool heater, and especially those using high-efficiency condensing technology, is naturally very acidic, so the materials used must be able to withstand the corrosion caused by these environments.
Heat exchangers inside most pool heaters are made of copper, which is a highly desirable material for heat transfer, but is very susceptible to corrosion. By comparison, high efficiency residential hot water heaters for homes typically use high-grade stainless steel, which is not as susceptible to condensate corrosion. In contrast, pool heaters need more material for heat transfer because they have to heat a lot more water than typical residential water heaters. Further, it would be cost prohibitive to put the required amount of stainless steel into a pool heater to heat more than 180,000 L (50,000 gal) of water. Moreover, pool water chemistry is also proven to be harsh on stainless steel heat exchangers and could cause corrosion issues.
As a result, pool heater development teams have focused on emerging materials which can better resist corrosion in the pool environment, while also keeping them manageable in size and weight for installation professionals, equipment shippers and warehouse managers, and affordable for homeowners.
New gas swimming pool heaters have a standard test they go through to determine their energy efficiency based on their Btu (British thermal unit) output.
Heater efficiency is the ratio of usable output to energy input. For example, an 80%-efficient heater uses $80 worth of useful heat for every $100 worth of fuel. Therefore, it wastes 20% of the fuel.
Most gas pool heaters feature their efficiency percentage on their nameplates. A pool heater’s manufacturer can also provide its efficiency percentage.
Today, you’ll find some gas pool heaters with 89%–95% efficiency. The following table shows how much you can save for every $1,000 in annual pool heating costs by installing a gas pool heater that’s 95% efficient. https://bluewaterspoolservices.com/best-pool-heater/