There are a few ways pool and spa owners can save money on energy of which
two are turning the circulation pump off when the pool or spa isn’t being used (or at least lowering the speed) and lowering the temperature of the water when the pool or spa isn’t being used.
Lowering the temperature during the keep out hours can easily save as much as
$200 per month or more. To do this you need a temperature controller that is set up for the days of the week type of control with the ability to set the time to lower the temperature at night and the time to set it back in the morning. It will need to be set back at least an hour before the opening hour to make sure the temperature is back to normal. A side benefit of lowering the temperature at night is that will reduce usage of the pool or spa during those hours. Imagine sneaking into a spa late at night long after it is closed only to find the water is 90°F instead of 104°F.
Most commercial pools and spas keep the circulation pump running 24 hours per day. Most of these pumps are over sized and turn over the water more than needed but that is the way it is. A variable speed pump can save a lot of money as you can lower the speed to get the desired turnover rate which could be every 6 hours. A better approach is to let the pump run at full speed when the pool or spa is open, and then lower the speed when it is closed. To do this right would require the ability to be able to set the open and closed times for each day of the week.
There are controllers for heaters and even some heaters have it built in the ability to have two temperature setpoints to realize the savings in lowering the temperature during the pool or spa closed hours. The same also goes for the variable speed pumps.
The PoolWarden is a water chemistry controller, meaning that it measures pH and ORP and controls relays that can feed corrective chemicals to keep the water chemistry in balance. The PoolWarden also has energy management built in allowing for control of up to three of any combination of heaters and variable speed pumps. There are two time profiles (supporting if you have a pool and spa with different operating hours) that include a morning time and evening time for each day of the week. When the time is between these two times the heater or pump will be running normal, when not between these two times the heater will be at a lower temperature and the pump will be at a lower speed.