Is a 2 speed or variable speed pump worth it at $0.082/kWh?

[Jeff111]

I'm looking at building a 20x40 pool with an 8' deep end and possibly a spillover spa. I think that means I will need a 2 HP pump. Our electricity is fairly cheap at a total of 8.2 cents per kWh (Nominally it's 5 cents/kWh but with the "fuel surcharge" and what not it works out to 8.2). Should I even be considering a variable speed pump? I like the idea of a quiet pump that's inexpensive to operate but I don't like the idea of an electro-mechanical device that's totally dependent on electronics with somewhat questionable reliability to run.

Would it even be worth the upgrade to a 2 speed at those electricity prices? 2 speed pumps are much simpler right? Would I still get me the majority of the efficiency benefits of a VS but with a simpler piece of machinery that, all other things held equal, is likely to last longer?

Thanks,
Jeff

 

[Bama Rambler]

While I don't think a VS pump would be cost effective, a 2-speed would if for no other reason than you could run it 24 hours a day for about the same cost as running a single speed 8 hours a day. It will also be much quieter on low than on high, so if noise is a concern there's another reason to get it.

 

[bobodaclown]

2-speed and don't look back.

 

[peterl1365]

If you're building a spa, then it might be possible to use a single VS pump for the entire installation rather than having a separate pump for the spa. I'm no expert on pool/spa construction, but I seem to recall that many installations used a booster pump to generate the pressure for the spa. It's possible that a good VS pump could fill that role.

Other than that, I don't think a VS pump would save you any money over a 2-speed. The 2-speed motors should be very reliable. A 2 speed simply uses a different winding configuration to run at half-speed, so it's not much more (cost-wise and complexity-wise) than a single-speed motor. You just have to carefully assess your power needs and don't buy too much of a pump.

Having said all that, I do like the ability to fine-tune my flows. I run my VS pump at around 2200 RPM for skimming and vacuuming a couple of hours a day, and at 1100 rpm for slow filtering 10-12 hours per day. With a 2-speed, I believe my only choices would be 3450 or 1725 rpm, neither of which would be optimal for what I wanted to do.

p.s. I'm envious of your power costs. My electicity is charged on a tiered scale, with the top tier being around 40 cents/kwh. For all intents and purposes, the cost of running my pump falls into that tier.

 

[JasonLion]

Even with a spa, the two speed works out to a lower lifetime cost. With a spa you need to size the pump so that high speed is optimized for the spa, which eliminates the need for a second pump, and then run the pool on low speed when you are not using the spa.