break even time for variable speed vs 2 speed

[scott_home]

Hi all,

According to APSP Pump Database Web Site, these are some of the numbers for Intelliflo VS and WhisperFlo dual speed 2HP.

Curve A:
Intelliflo at 1100 RPM: 24 GPM, 145 W
WhisperFlo at 1725 RPM: 37 GPM, 395 W

I assume these measurements are tested under similar conditions (ie. TDH). So I can assume a similar saving ratio at anyone's house.

At $0.12 /KWh, the annual cost to run these two pumps to turn over a 22500 G pool as follows:
Intelliflo: 22500 / (24*60) = 15.625 hours per turnover.
145 W * 15.625 = 2.27 kWH / day
2.27 * 365 * $0.12 = $99 / year

WhisperFlo: 22500 / (37*60) = 10.135 hours per turnover.
395 W * 10.135 = 4.00 kWH / day
4.00 * 365 * $0.12 = $175 / year

At these settings, I will save $76 / year to run an IntelliFlo vs WhisperFlo dual speed. The price difference between the two pumps is $200. So it takes about 3 years to break even. However, quite a few users said that it is unlikey to break even when the utility rate is under $0.15 / kWH. Am I missing something here?


Scott

 

[duraleigh]

Am I missing something here?

In the larger scheme of pool costs, you might be over thinking it somewhat. There are so many variables involved that I think you would make a better decision to get the pump that seems to suit you best based on other factors other than electric consumption.

The ROI on VS pumps makes a comparison on VS pump cost as opposed to a single speed pump cost......not comparing two VS pumps.

 

[scott_home]

If I were to get a single speed pump, it needs to be 2 HP because I have a SPA and pool. Based the numbers of the same website, to run one turnover per day, it would cost about $480/year, so it is not even in my consideration list.

In the calculation, I already considered the minimum flow requirement of SWG and my pipe size. Can you tell me what other variables or factors I should consider? I am really new to owning a pool. What my calculation tells me is that the total ownership cost of the pump (cost of pump + operating cost in a period time) is cheaper to own Intelliflo if it runs without any problem for at least 3 years. Make sense?

 

[mas985]

It all depends on the assumptions. There are a few things that are pushing up the costs of the two speed for you but given the conditions you set up, your calculations are correct.

The major cost increase is the 2 HP requirement for the two speed. However, most people looking at this trade off do not have the 2 HP pump requirement so a smaller cheaper two speed is an option. If you were to run the numbers on a 3/4 HP Superflo, you would find the break even to be much longer.

The "rule of thumb" is to capture the majority of people doing the comparison but I always like to look at the details to make sure everything is being taken into account.

BTW, I have a spreadsheet in my sig that uses both the CEC and APSP test data to do and easy cost comparisons on several different pumps if you are interested.

 

[scott_home]

I guess one of the most important cost factors is reliability. I wonder how durable the IntelliFlo electronics is...

 

[mas985]

VS pumps in general have electronic components which susceptible to power line spikes and surges so a surge protector is highly recommended. There are many on this and other forums that lost their drives due to lightning strikes. A two speed pump is much more forgiving and much cheaper to fix when something does fail.