Peter,
You haven't priced variable speed pumps if you are asking to spend $500 or less. So if that is your criteria, you can stop right here because you won't find one for that price. You might get a 2 speed pump at that price and you would need a controller to switch between the 2 speeds. All the variable speeds work in terms of saving you money on utility bills. The question is how you plan to use the pump and how will the cost projections work out for your particular pool and uses. Every pool is slightly different. I have a variable speed pump (only installed for 2 weeks) and I am still tweaking it. I'm not one of the advocates of running the pump 24X7. I run mine at 40 gpm which equates to 1 turnover in 13.3 hours (I don't run the pump that long - right now, I am at 8 hours running time and water quality is fine).
I had a 1.5 HP single speed pump. For 1 turnover, it consumed 16.2 kwh (at $0.27X16.2kwh=$4.37/day, $1595/year). With current setting for my variable speed, it consumes 6.9 kwh per turnover (.27X6.9=$1.86/day, $678.9/year). But that's for a 32K gallon pool. If I ran half my time at a higher speed for feeding a 2nd story solar (say 50 gpm - around what a modern half HP motor puts out) and half at 30 gpm, my annual cost is about the same as running at 40 gpm the whole time. If your pipes and equipment was exactly like mine but with a 15K pool and you ran 1 turnover/day, payback would take 3 years or more.
To get the $200 rebate, you have to have the pump installed by a licensed contractor. In SoCal, they charge around $400-500 to install so don't think of it as getting a discount on the pump, it is a discount on the installation. Fortunately, Pool Services Technologies gave me a TFP member discount on the install. If you don't know someone that is willing to discount, then skip the rebate and install it yourself if you know how. Total cost to install, figure on $800 to $1200 for the pump plus $400-500 for install minus $200 rebate (and remember that the rebate is only good as long as they have funds).
I'll narrow it down to 3 for you - Hybrid Pumps, Jandy ePump and Pentair (SVRS or VF, your choice). The Hayward is less expensive but I was advised to stay away from Hayward pumps by several pool professionals.
As Mark stated, the cost projections by the vendors are assuming you have X configuration and are running the pump at max efficiency only filtering the water. I've given you my real life example and there are several people that have detailed postings of their Pentair with rpm/gpm/watts listings so you can do your own comparison.
