I am about to choose a PB for my 15x35 fiberglass salt water pool and need to make a decision if I should go with the standard 1HP pentair whisperflo pump or upgrade to the variable speed intelliflo 8 speed variable pump for an additional $700 (total cost is $1,000 but my energy company will reimburse $300). Are they really that much more efficient? By the way my electricity cost is 9.7 cents/kWh in winter and 14.9 cents/KWh in the summer during peak hours at highest rate for more than 2,500 KWh/per month, 13.1 cents between 1,500 and 2,500 KWh (by the way my total consumption now without the pool is 1,750 KwH during summer months at peak A/C usage).