Spas are really nice things to have, but if they are not designed properly, they can cost you a lot to own.  There are many  aspects to these costs and some are hidden by the spa manufacturers by they way the spas are designed.  In the last article on filtering myths, I went over in detail the myth of 100% filtering and the advertising used to sell it as if it was a good design.  If you have a poorly designed spa with a tiny circulation pump on it, it will cost more in chemicals to keep the water clear and sanitary.  That is fact.  It either costs in chemicals and supplies, in water changes, or in wasted time.

If a spa uses less chemicals to keep the water clean, then it costs less in both chemicals and in water changes.  If your water is using more shock, chlorine and has to be drained and filled more often because of the total dissolved solids.  This is from too many chemicals.  Then it becomes more expensive just because of the cost to heat up the water and the cost of the water and the cost of chemicals.  In a spa that filters correctly you use a lot less chemicals, a lot less time and a lot less water.   If your spa is constantly clouding up and all the chemical tests are correct, then you need to filter more or filter better.  A spa that filters well uses less products.  It can go longer between drain and refill and the extra costs of heating cold water up to temperature.  Also a spa that runs correctly to the ANSI standard with correct filtering per day has water that is safe!  You will not be soaking in dead skin tissue, mucus, feculence, sweat, and hair, like the cheaply made spas that barely filter.

It is important to note that the human eye cannot resolve (see) smaller than about 1/1000 of an inch with perfect vision.  Most folks resolve about 3 to 4/1000 of an inch maximum.  20 microns is 20/1000 of a millimeter.  The filters remove most of the debris from 10 microns on up if you use them properly.  More on filters later.
The point of this is the water can look clear to the naked eye and still have many things floating in it that you cannot see.  When people talk about "crystal clear" water, you need to take a gallon jug and put some filtered tap water in one and a gallon of spa water in the other and compare the clarity that way.   That crystal clear spa water may have a gray look side by side with pure water.  

The secret to getting large volumes of water filtered and qualty of water, is to conserve the energy from the filtering pump and transfer the heat into the spa water.  At the same time while the pump is running it creates a 100% thermal heat barrier on all the pipes, and the vessel of the spa.  There is literally zero heat loss from the spa water, except out the top where the cover is.  (Use a thermal blanket with a spa cover is the smartest thing a person can do in winter to supplement the hard cover.)

Normally during the entire filter cycle the heater never comes on, because the spa is heated and fully insulated by the kinetic and thermal energy of the pump.

If you  run our largest pump on low speed, it can run for 7 hours to equal the same kilowatt hours as one hour of electric heat.  In most spas the heater and the pump is used to heat the water.  The 5.5 KW or 4 KW heaters are the most wasteful part of spa operation.

When it is extremely cold, I advise my customers to run the filtering 24 hours per day and they can save up to 20% of the energy and have extremely well filtered and ozonated water.  This brings the thermally closed DAIT spa with a full size 5 HP  pump to about  2/3 the cost of a normal full foam spa with two 2.5 HP pumps and in the coldest winter months.  If a full foam spa costs $100 then the DAIT will cost $66.  

In the Highest Quality Super Custom models we use a very special pump for filtering and heating.  It is a modern engineering "marvel"  It moves a tremendous amount of water with an extremely low amperage.  It is designed with large cutting impeller so that it has a high volume and very low pressure.  In filtering the pressure is not needed but the total gallons is very important.  In the SCF model we are getting reports of extremely low energy costs because this pump creates a 100% thermal warm air barrier for a lot less than the large pump does and it does it 24 hours a day.  It filters from 35,000 to 50,000 gallons of water per day and the ozone system on this spa is so effective that the use of chemicals is absolutely minimized.  The reports from customers on this spa are simply a reflection of the hard work in the design and production of this masterpiece of spa engineering.  While I set back and listen to the competition tell me that "it can't work".  The customers testify that it does work, extremely well.  The SC spa owners are totally spoiled.  If a standard full foam spa costs $100 then the DAIT SCF will cost $50 and still filter 10 times the water of the tiny circ pump spas that tout 24 hour filtering at 3 to 7 gallons per minute.  

In a full foam spa, the problem is they are relying on normally a softer foam that has an R value of 1 or 2 per inch.  and saying that it is the "BEST".  Take a look at this picture below.  I want you to look where the manifold is in relation to the outer wall of the spa.  The other side of the manifold is directly opposite this one pointing in the other direction.  The water comes up directly from the jet pump and is pump through this area while the spa is used and during the set filter cycles on pump one.  In this photo you can see that this is similar to a radiator with a lot of exposed pipes very close to the outside of the cabinet. You can see that this spa has a huge volume of water passing about 2 inches from the outside world, and is covered in about R-4 worth of foam.