The pool pump is the largest electrical load on most properties that have one — often larger than the air conditioning over a season, because it runs for hours every day at a steady draw. That makes replacement a running-cost decision far more than a purchase-price decision.
What it costs
| Item | Typical |
|---|---|
| Single-speed pump, unit only | $250 – 600 |
| Two-speed pump, unit only | $450 – 900 |
| Variable-speed pump, unit only | $700 – 1,600 |
| Installation, straight swap | $200 – 500 |
| Installation with new plumbing or electrical | $400 – 1,200 |
| Variable-speed, installed | $1,100 – 2,600 |
| Motor rebuild / motor only replacement | $300 – 700 |
Typical US pricing at the time of writing, not quotes.
Note the rule that has already made this decision for most people: US federal efficiency standards for dedicated-purpose pool pumps effectively removed conventional single-speed pumps above a modest horsepower threshold from the market. For most in-ground pools the replacement is a variable-speed unit whether or not you were planning on one. Many utilities also offer rebates of $100–400 on variable-speed pumps — worth checking before you buy, not after.
Why variable speed wins on arithmetic
Pump power follows the affinity laws: flow scales with speed, but power scales with roughly the cube of speed. Halve the speed and you use about an eighth of the power — while moving half the water, so you simply run longer.
The turnover is the same. The energy is not.
| Single-speed 1.5 HP | Variable-speed at low RPM | |
|---|---|---|
| Draw | ~1,500 – 2,000 W | ~150 – 400 W |
| Hours/day for one turnover | ~8 | ~12 |
| kWh/day | ~14 | ~3.5 |
| At 18 ¢/kWh, per season (180 days) | ~$450 | ~$113 |
A saving near $340 a season against a purchase premium of roughly $600–1,000 pays back in under two seasons, and the pump lasts eight to twelve years. See variable speed pump savings for the full working, and how much does it cost to run a pool for where the pump sits against heating and chemicals.
The quieter running is not a minor point either. A variable-speed pump at filtration speed is close to inaudible; a single-speed at full draw is not.
When to replace rather than repair
Repair is reasonable when: the motor is under about six years old and the failure is a seal, a bearing or a capacitor; the wet end is sound; and the pump is already variable-speed.
Replace when: the pump is single-speed and out of warranty — a rebuild spends $400 to keep the expensive-to-run option; the housing is cracked; the motor has been through more than one rebuild; or the pump is oversized for the pool, which is extremely common.
Oversizing is the norm, not the exception. Pumps have historically been specified far larger than the plumbing can use. A 2 HP pump on 1.5-inch pipe cannot move its rated flow — the pipe chokes it — so the extra horsepower is converted into heat, noise and electricity bills. Replacement is the moment to fix that: size to the pool volume and the plumbing, not to the label on the old unit.
Sizing it properly
Work from turnover, not horsepower. Take the pool volume — see how to calculate pool volume in gallons — and size for one turnover in 8–12 hours at a flow the plumbing can carry.
Rules of thumb for maximum flow before pipe velocity becomes a problem:
| Pipe | Practical max flow |
|---|---|
| 1.5 in | ~40 – 45 GPM |
| 2 in | ~70 – 80 GPM |
| 2.5 in | ~110 – 120 GPM |
A 20,000-gallon pool needs about 28 GPM for a 12-hour turnover. That is comfortably inside 1.5-inch plumbing, and it is a fraction of what a 2 HP pump wants to deliver.
Also check the filter and heater ratings — pushing more flow than the filter is rated for shortens its life and does not clean better.
What the installer should confirm
- The new pump's flow curve against your plumbing size, not a generic recommendation
- Whether the existing electrical supply suits the new unit
- That the union fittings line up, or that new plumbing is in the quote
- Whether a utility rebate applies and who files it
The short version
Budget $1,100 – 2,600 installed for variable-speed. It pays back the premium in under two seasons on a typical pool, it is what the market now sells anyway, and replacement is the right moment to stop running a pump two sizes larger than the pipe can use.