Variable-Speed Pump Savings Calculator

Each pump's running cost is the same cost-of-electricity identity, applied to both and then differenced. Convert watts to kilowatts, multiply by the daily run hours to get kWh/day, multiply by the season length for kWh/year, then by your rate for $/year. The annual savings is single-speed cost minus VS cost; the payback is your net upfront cost divided by that savings.

per pump:  daily_kWh   = (watts / 1000) × hours/day
           annual_kWh  = daily_kWh × season_days
           annual_cost = annual_kWh × rate_per_kWh

savings:   annual_savings = annual_cost_single − annual_cost_vs
           net_upfront    = max(0, premium − rebate)
           payback_years  = net_upfront / annual_savings   (savings > 0)
           10-year net    = annual_savings × 10 − net_upfront

Why a variable-speed pump wins. A pump follows the affinity (cube) law — halve the speed and you move about half the water for roughly an eighth of the electricity. But a VS pump runs longer at low speed to move the same total water, so a naive "divide the cost by 8" overstates the savings. This tool avoids that: it uses the average watts and run hours you enter for each pump, which is far more defensible than a cube-law shortcut. Enter the VS pump's average draw at filtration speed, not its nameplate peak.

A note on the claims you'll see elsewhere: manufacturer calculators often headline "up to 90%" savings and "payback in 2 years or less." Those are fixed marketing figures. We anchor energy reduction to the realistic 50–75% band (80–90% is a theoretical ceiling), and the payback you read is derived from your own price premium and rebate, not a generic claim. Rebates of $100–$900 materially shorten payback, so plug in your utility's actual offer. This is an advisory estimate, not a guaranteed bill — real results depend on plumbing, your schedule, and your tariff. The HP entry option is a labeled estimate (W = HP × 746); nameplate HP overstates real draw.

Sources: Pool Goods — Variable Speed Pool Pump Energy Savings: Real Numbers by Pool Size; Pentair — Pool Pump Savings Calculator; Buds Spas — variable-speed pump savings comparison.