This summer I've found a lot of air conditioning coils that need cleaning, and I've cleaned most of them. I've been too busy to keep track of the pollen counts, however I suspect that the unusually high outdoor temperatures simply revealed this problem and that the air conditioning coil problem was there all along, or at least a few cooling seasons.

Your air conditioner is oversized for most of the year, so if its not quite up to snuff you may not notice. When its 100 degrees outside you will notice. My electric air conditioning cost was up about 25% over last July. Using the degree day method I figure this is about normal. High but normal.

Now to the reason I'm writing. When I quote a coil cleaning I have three tiers ranging from about 60.00 to over 100.00.
If the hose is handy to the air conditioner or if its the second unit near the first this is about 60.00 if I need to drag out and put up my own hoses the cost goes up to about 88.50, If difficult access, or landscaping makes it difficult access the cost of service goes up.

Can I clean it myself?... I hate to limit anyone. Yes, but you have to know how. What do you use? Sodium Hydroxide, sounds like a serious chemical? Yes its very dangerous. Where can I get some of this stuff? This is a time when I am tempted to tell a lie. I want to say that its only available to air conditioning servicemen, but you can buy it online now and I wish you couldn't.

Don't get me wrong. Save your money is my motto, and I would be ashamed to do something for pay that you were willing and able to do yourself.

Coil cleaning is not for amateurs, and trained servicemen are hurt by careless coil cleaning procedures. I have a 4.5 cm x 2mm scar on my left foot to prove that after 30 years of HVAC service experience you can still get hurt.

Sodium Hydroxide is a strong alkali, you may call it caustic soda, or lye. It comes to the serviceman in a concentration of between 10 and 30%. (I got hurt trying to dilute it when I spilled some over my funnel and onto my shoe), in a working solution which is usually much stronger than needed it is still almost as dangerous.

If you get one drop in your eye, you have lost your eye. 
If you get one drop in your eye, you have lost your eye.

You may know (if you are truly southern) or a well read yankee that we used to make soap of filtered ashes for the lye and animal fats and oils, which it readily dissolves.
When you use this stuff and get some on your skin it will not wash off easily, and until it does you will feel a slippery substance on your skin. This is the sodium hydroxide making soap out of you!
Again this slippery stuff is not the cleaner, it is in fact your own flesh that is now soap.

So you will be careful not to get it on you, I use elbow length heavy black rubber gloves and wear glasses.
First aid is rinsing with water for at least 20 minutes. An acid like vinegar at about 5% is effective for the diluted solution, as a means of neutralizing the alkaline.
There can be a violent reaction with a stronger solution undiluted hydroxide or acid, I have not seen this but, I'm sure I don't want to.

Add this alkali to the water, just as you would an acid, not the other way around. One reason is splashing, the other is an exothermic reaction that occurs in water before it dilutes the hydroxide. Also, in the dedicated sprayer I have for this air conditioning outdoor unit only there has only been water and coil cleaner. What was in your sprayer is unknown, the possible reaction is unknown. Don't smoke while cleaning coils or mixing this stuff, there will probably be hydrogen present, not much, but Hey!.. If you don't remember high school chemistry use logic. When you start adding water to acid or alkali the concentration starts high for a very exciting initial release of heat. If you do it the right way the concentration starts low.

I clean coils, I work with respect for the material, I always, always have a hose hooked up and checked for flow rate before I even take this stuff off the truck. You could need it urgently at any moment. If you want to do this work you will have to look on YouTube for instructions that are step by step. Put what I just said next to what you learn on the tube as a safety message. I prefer not to offer instruction except in person, and if I'm there anyway why not clean the coil?

P.S. If you have a hose hooked up next to my unit, and no Holly bushes or Rose bushes around my unit, this will be the least expensive and safest way to do this work. Currently 58.50 USD

Invest your money in safety,
Ed Cline