SDG&E Rates and Pool Schedules

As everyone knows, pools are expensive. Pool pumps especially are expensive to run. Usually the pool owner sees that their pump is the most energy demanding appliance in their house. Thankfully there are a few very effective ways to reduce the electricity demand we have in the backyard. Just as a reminder, like you have read in other blogs, clean filters are mandatory and variable speed pumps can be game changers. 

Knowing these two facts we can also take advantage of SDG&E’s peak pricing structure and achieve serious savings. The below image is the pricing schedule that our utility company uses. There are actually 3 different structures but the most important element is essentially the same. SDG&E would like us to use less power from 4 to 9 PM.

This obviously means that it is cheaper to run your pump in the mornings to mid-afternoon, and late at night. Looking at this image one might jump to the conclusion that ‘I will just run my pump from 12 am to 8 am, that’s 8 hours and I should be able to turn over all the water in my pool in that time’. And since most of that is super off peak rates we assume we will save a fortune. 

However it is not that simple. I have had pools in the past with  programmed systems running this schedule but usually after a couple weeks the pool no longer looks its best. This is when I usually get a call or a text asking if there is something wrong with the pool chemistry or filter. When in fact it is a problem with circulation, not filtration or sanitization. 

The problem with running your filter overnight or for just part of the day, is that the water sits motionless in the hottest parts of the day. From 4-9 pm (peak hours) we are currently still getting 5-6 hours of sunlight on the pool. 2-3 hours of that are during the actual hottest parts of the day. This means your water sits under the sun motionless. These are the exact conditions for algae growth. Think about the heat in your house at that point in the day, usually this is when we need to run the air conditioner. In fact this is partly WHY the peak hours schedule exists. Remember back to the filtration blog, a clean pool has three necessities; filtration, circulation, and sanitization. It is not enough to just have 2 of the 3 elements, and this is how to solve circulation.

Thankfully we have variable speed pumps. Meaning we can turn the pump down to a low speed and cut the power demand on the system. Oftentimes by an even larger factor than the corresponding rate increase. Allowing us to continue moving water during those hot hours without impacting the power grid too much. Refer back to our variable speed pump blog for more information on variable speed and flow pumps. 

No two pools are the same and each has their own flow dynamics but if there were a perfect schedule for every pool based on gallons and it would look something like this. (qualify this statement a little more

0 understand the turn over, and peak hours 

6am - 12 pm: 6 hours at 20 GPM

12 pm - 4 pm: 4 hours at 40 GPM 

4 pm - 10pm: 5 hours at 10 GPM (double check this is allowable)

We must filter all 20k gallons

We must circulate during hottest hours of the day

We want to minimize cost during peak hours 

Running this schedule allows us to do all three things we are hoping to accomplish. Pools are not an exact science, by nature each pool is a unique open environment. So this schedule may require some tinkering to for your pool specifically. As long as the three points listed above are covered you should have a happy healthy pool.... and wallet!