Ask five pool owners how long their pump should run in July and you will get five different answers, most of them guesses. The real number is not a mystery. It is 8 to 10 hours a day in a Phoenix summer, sometimes more depending on pool size and load, dropping to roughly half that in winter. That range comes straight from equipment and industry guidance built for exactly this climate, not a one-size-fits-all national rule. The harder part is not the hours themselves. It is figuring out when to run them without handing your utility a peak-rate bill on top of a peak-heat one.
Why 8 to 10 hours, not 4
A pool pump’s job is turnover, meaning cycling the entire volume of water through the filter at least once, ideally more, every day. In cooler months that turnover can happen in 4 to 5 hours because the water is not under much biological pressure. In a Phoenix summer, with water sitting in the high 80s and 90s for weeks at a stretch, that same volume needs more passes through the filter to keep up with what is growing and what is getting burned off. Cutting the runtime to save power in July is one of the most common ways a clear pool turns into a problem pool, and it usually shows up as cloudy water or a chlorine reading that will not hold, days before it shows up as visibly green.
Circulation is what actually fights algae in 104 degree weeks
Chemical balance gets most of the attention, but circulation is doing just as much work. Algae spores and organic debris need still water and a nutrient source to take hold. A pump running long enough to keep water constantly moving past the filter and sanitizer disrupts that before it can establish, the same way a river resists algae better than a stagnant pond. Heat also degrades chlorine faster than people expect, so the sanitizer you dosed at 8am is not doing the same job it was at noon in a 104 degree week. Longer circulation time is how you cover that gap. Shortchange the hours and you are asking a shrinking dose of chlorine to protect water that is working harder against you every hour the sun is up.
Where the electric bill comes in
Here is the tension: running 8 to 10 hours a day, every day, all summer is real electricity, and both major West Valley utilities charge more during certain hours. The good news is the pump does not care what time it runs, only that it runs long enough. That means the fix is scheduling, not cutting hours.
APS: the easy one to plan around
If you are on APS, their residential Time-of-Use plan makes this simple. On-peak is only 4pm to 7pm on non-holiday weekdays, three hours a day, five days a week. Every other hour, including all of nights, mornings, and every weekend, is off-peak. Some seasons also carry a super off-peak window from 10am to 3pm on winter weekdays at a lower rate still. Practically, that means an APS customer just needs to make sure the pump is not actively running between 4pm and 7pm on a weekday. Everything outside that three hour block is fair game. Confirm your exact plan details at aps.com, since APS offers more than one plan structure.
SRP: check your plan name first
SRP customers have more homework here, because SRP runs several different residential time-of-use plans and they do not share the same peak window. Some plans put on-peak hours in the afternoon, others put them in the evening, and the exact times shift depending on which plan a given account is enrolled in. Rather than repeat a single window that might not match your actual bill, the safest move is to pull up your own SRP price plan by name at srpnet.com and confirm your specific on-peak and off-peak hours before building a pump schedule around them. Running a pump on the wrong assumption about SRP’s peak hours is an easy way to end up paying peak rates without realizing it.
A practical split schedule
Once you know your actual peak window, whether that is APS’s fixed 4pm to 7pm or your specific SRP plan’s hours, the schedule itself is straightforward. Split the 8 to 10 hours into two blocks that avoid the peak window entirely, for example running heavier overnight and again in the mid-morning before peak hours start, or running through the afternoon and stopping cold right before peak begins. A timer or a smart controller set once will hold that pattern automatically for the rest of the season, so this is not something you have to think about daily once it is dialed in.
If you are still running a single-speed pump
Everything above applies to any pump, but a variable speed pump changes the math. A single-speed pump runs at full output any time it is on, so every hour costs the same. A variable speed pump can run longer at a lower RPM for the same or less total energy, which gives you more flexibility to stretch circulation time across off-peak hours without the electric bill climbing in proportion. If your system is still single-speed and due for a repair or replacement anyway, this is worth factoring into that decision alongside the runtime and peak-rate math above.
Getting a timer or automation system dialed in correctly for your specific plan and pool is exactly the kind of thing we set up as part of ongoing filter and equipment care. Read more about our filter and equipment care.
