I'm looking at replacing the pressure side cleaner with a robot myself, and I just wanted to follow up on the cost question:
My pool currently uses a Polaris 280, with a PB4-60 booster pump. The booster pump is failing and making noise, showing corrosion around the edges, etc... it's needing a replacement rather than a rebuild. The 280 is roughly the same. It's doing an okay job, but really probably due for a full rebuild/replace. Due to pool shape, it misses about 30% of it, even with the new longer hose with all new swivel joints that I put on a few months ago, thinking that was the problem.
So if a Polaris 280 factory rebuild kit is $350, and the replacement pump is about $450. That's $800 if you rebuild, plus 3 hours of work or so to replumb, rewire, and rebuild it. If you buy a new 280 instead, it's $600 instead of $350, and then you're looking at $1050.
It's been running 4 hours a day to try to clean everything (and still misses 30% or more). 230V at 6.4A is 1472 Watts per hour, or 1.472 kWh, * 4 = 5.888 * .15 cents per kWh power usage is 88 cents per day, * 365 days per year is about $322 per year to operate.
The Dolphin S200 (Minimum Advertised Price $1049) uses 180 watts per hour, so assuming it runs the same amount of time, 180W * 4 = 10.8 cents per day, * 365 = $39.42 per year to operate with those assumptions, so hour for hour you'd save ($322 - $40) = $282 per year in electricity.
So it seems like, if you paid $1049 for the Dolphin S200 and rebuilt the Polaris and installed another PB4-60, you'd spend $249 more up front (and save 3-4 hours of nasty work), and then by the end of year one, you'd be $33 to the good, earning $282 per year after the fact that it runs.
Which means that, if the robot lasts 4-5 years, as anecdotal evidence seems to bear out, your energy savings alone will pay for the robot ($282 * 4 = $1128), before you even begin to consider the cost of maintaining a 280 (rebuild $350 or replace $600 every 4-5 years like the robot) and the booster pump, which lasts somewhat longer (call it $450 every 10 years, which makes the overall cost $45 per year or $180 for 4 years).
Again, those are the apples to apples assumptions. Other things that will skew the needle one way or the other, or are intangible:
- Robots are advertised as only needing to run every 2 or 3 days, which increases the value proposition even more, but:
A. I'll believe it when I see it
B. Operating cost is so low already that it doesn't provide a significant difference, even if $39.42 per year drops to $20 or $15, that's only another $80 over the life of the unit, if it's even true.
- If I stay with the Polaris setup, it'll still likely leave a large portion of the pool untouched. It's a problem that's always existed, not a new one as the system started to fail
- I've had a pool in two houses for the past 12 years or so, and 4-5 years is about all I have managed to get out of the Polaris 280, which puts it on par with the Dolphin.
- The booster pump DOES last longer than 4-5 years, but not much longer. This failing one is one I put in shortly after we moved in, which was about 6 years ago.
- For MOST people, replacing the booster pump means paying someone, due to high voltages and pool plumbing. A handy person can do it, otherwise, it's likely $300 or more in labor.
- In the past 4 years, I've replaced a couple of wheels on the Polaris, and gone through about a dozen net bags where the zippers rust off and break or the bag gets giant holes in them.
This SEEMS to bear out that on a full replace, a robot makes sense, where if you have a fully functional cleaner it's more or less a matter of preference because you don't really come out ahead (until it's time to replace). Also that it will favor the robot more and more as the cost of electricity increases. My opinion would be that it's not worth switching to a robot if everything is working well, but if any piece breaks, it's financially worth swapping.
Does that reasoning make sense, or is there something I'm not considering?
Someone mentioned SWGs above and how it was similar. I actually did a similar cost-benefit on those when I was considering it as well. When we moved in the SWG wasn't programmed to run and the previous owner (or their pool service) was running it as a chlorine pool with tabs. I found even buying tabs in bulk, I found I was spending $40-50 a month in tabs to get the chlorine levels where they needed to be. Even counting non-swimming months I found that I could replace a SWG cell every other year and still break even over having to dose chlorine every week.
