Price drivers
What actually moves the number, run through this site's own model
Every row below is the same 512 sq ft default pool in Phoenix, AZ, run through this site's own engine with exactly one input changed at a time. Nothing here is a rule of thumb — it is the computed heat-pump season cost, before and after, for the specific choice named.
Operating-cost drivers, computed rather than asserted
| Driver | Comparison | Lower case | Higher case | Spread |
|---|---|---|---|---|
| Season length | 123 days vs. 303 days | $570 | $3,830 | 6.7× |
| Cover use | None vs. a bubble cover on 14 hours a day | $294 | $1,662 | 5.7× |
| Wind exposure | Sheltered (walled yard) vs. fully open (lakeside, ridge, desert lot) | $1,036 | $3,409 | 3.3× |
| Water temperature | 80 °F vs. 88 °F | $1,057 | $2,400 | 2.3× |
Read the spread column as a ranking for this specific set of comparisons, not a universal law — a bigger swing in the input naturally produces a bigger swing in the cost, and the four comparisons above were not chosen to move by equal amounts. Ranked by the table's own numbers: season length moves the bill by 6.7×, cover use by 5.7×, wind exposure by 3.3×, and an eight-degree setpoint change by 2.3×. None of these four are equipment purchases — they are decisions, free to make, and on this pool they outweigh what a bigger or more efficient heater would do to the bill.
- Season length. The largest single lever in this comparison, because it is also the comparison with the widest range behind it — every added week adds its own loss term on top of the ones already there. Covered in full, with the marginal cost of each added week, on the season length page.
- Cover use. Close behind season length here, because a cover run honestly suppresses the single largest loss term in the model almost entirely. The cover page breaks this down by cover type and by the hours it is honestly on, not the hours it is theoretically on.
- Wind exposure. A hedge, a wall or a windbreak between the pool and the prevailing wind is worth more than most equipment upgrades, because evaporation is the loss term wind drives directly. See the climate page for why the regional wind figure itself is the least trustworthy number this site uses, and why the exposure control exists as an override.
- Water temperature. The smallest of the four in this particular comparison, but still more than double for an eight-degree change, because every degree above what you actually need widens the vapour-pressure gap that drives evaporation and the effect compounds — the top few degrees of a setpoint are the expensive ones.
What the drivers do when they stack
None of the four rows above happen in isolation on a real pool — a site is sheltered or it is not, an owner covers the pool or does not, all at the same time. Running the same default pool at every "cheap" choice at once — sheltered wind exposure, an 80 °F setpoint, a 123-day season — against every "expensive" choice at once — open exposure, an 88 °F setpoint, a 303-day season — shows how far the decisions compound on top of each other, before a cover or a different fuel even enters the picture:
| Configuration | Heat-pump season cost | Season length |
|---|---|---|
| Every cheap choice at once | $111 | 123 days |
| Every expensive choice at once | $8,661 | 303 days |
| Every expensive choice, plus a cover 14 h/day | $3,356 | 303 days |
The spread between the top and bottom rows is 78× — not because one owner bought a worse heater, but because four free decisions moved in the same direction at once. Even inside the expensive configuration, adding a cover recovers 61% of the cost without touching the season length, the wind exposure, or the setpoint at all. That is the practical takeaway: before pricing new equipment, check whether the current bill is actually an equipment problem or a stack of free decisions pointed the expensive direction.
What moves installed cost, in general terms
Everything above is operating cost, the half of the bill this site's physics can actually derive from your pool and a published energy price. Installed cost — what a heater costs to buy and put in the ground — runs on a different set of drivers that this site does not currently have a properly sourced figure for (see sources for why), so this section stays qualitative rather than putting a specific dollar number in front of you:
- Heater type. A resistance element, a gas heater, a heat pump and a solar array are not adjacent price points on one scale — see the equipment pages for what each one is actually built around.
- Existing utility infrastructure. Whether a gas line or a dedicated electrical circuit already reaches the equipment pad is frequently a bigger cost swing than the heater itself, and it is the item a phone estimate is most likely to have assumed rather than checked — see reading a quote.
- Local labor rates and permit fees. Both are set locally and both are genuinely variable across the country; this site does not have a checked figure to put a number on either one, so ask your own contractor and building department rather than trusting a web average for your specific city.
Two ways to read this page
If you are shopping for equipment, the installed-cost drivers matter more — they set what you pay once. If you already own a heater and are looking at a bill that seems high, the operating-cost drivers above matter more, and every one of them is something you can change this weekend without buying anything. Run your own pool's numbers on the main calculator to see which lever is actually the largest one for your situation; on this default pool it is season length and cover use, not wind, and your own pool's ranking may differ again.