What PoolBoss Says
It is worth it when the customer has the unshaded area for panels and wants a longer season rather than heat on demand. Solar costs the most up front and effectively nothing to run, with payback commonly inside about seven years. A heat pump wins when the heat has to arrive on a schedule.
The customer asks you, not a heating contractor. You are the one standing at the pad every week, so the question lands on you first, usually in October when the water drops under 80 degrees and the kids stop getting in.
Almost everything written about pool heating is written by somebody who sells one of the three options. What follows is the comparison without a thumb on the scale - what solar, a heat pump, and gas each cost to install and to run, and where each one quits - plus the part no homeowner article covers: which of that work a two-truck service company can take, which it should sub out, and which it should refuse.
At a glance
Key takeaways
- Recommend solar when there is unshaded area for panels and the customer wants a longer season rather than heat on demand.
- Size solar at roughly 50-100% of the pool's surface area in panels, and give a fast no when the area is not there.
- A heat pump runs about $3,000-$8,000 installed, costs roughly a third of propane to run, and often pays back in 3-5 years in a warm state.
- Below about 50 degrees ambient a heat pump loses its efficiency fast, which is the one argument gas still wins outright.
- Take the panels and the plumbing, sub out the 240 volt electrical work, and refuse gas line work every time.
- Quote the warm-up time with the equipment: days for solar, 24-72 hours for a heat pump, hours for gas.
- Tell them a cover is not optional on a heated pool, because evaporation gives back most of the heat overnight.
Is a solar pool heater worth it for my customer?
Yes, on a pool with sun, space, and a customer who wants a longer swimming season rather than a warm pool on a particular Saturday. Solar carries the highest up-front cost of the three options and effectively no running cost, because the only energy it uses is the pump you are already running. Energy.gov puts the payback inside about seven years and often well under that, which on a pool the customer intends to keep is a real return rather than a sales line.
The thing that kills the recommendation is area, not budget, and it is worth checking before anyone gets excited. A solar system is normally sized at roughly 50-100% of the pool's surface area in panels, so a 450 square foot pool wants something like 225-450 square feet of unshaded, reasonably south-facing roof or ground rack. If that does not exist, say so at the gate. A fast no costs you ten minutes; a quote that dies at the roof survey costs you a week.
- They want shoulder season, not January. Solar typically adds on the order of 10-15 degrees over an unheated pool and pushes the swimming season a month or two further at each end, which is the March-and-October request most customers are actually making.
- There is unshaded area of about half to all of the water surface. South-facing roof is ideal, a sunny ground rack is fine, a shaded north slope is a no.
- They plan to stay. A payback measured in years only counts to somebody who will still own the pool when it arrives.
- They can live with the weather deciding. Solar heats when the sun is out, and a cold cloudy week means a cold pool no matter what you installed. That is the same honesty test as the variable-speed pump recommendation: say out loud the condition under which it does not pay, and the customer trusts the rest of it.
Solar, heat pump, and gas each win a different argument
The pool heater payback question has three different answers because the three systems are not really competing for the same job. Solar buys a longer season for no running cost. A heat pump buys temperature on a schedule for a moderate running cost. Gas buys heat right now for the highest running cost of the three. A customer who says they want the pool heated has usually only thought about one of those, and your job in the next two minutes is to find out which.
A heat pump is the middle option and the one most Sunbelt operators end up recommending: roughly $3,000-$8,000 installed, with electricity that typically runs about a third the cost of propane and about half the cost of natural gas for the same heat. Against an existing gas heater that is commonly on the order of $150-$400 a month back in the customer's pocket during the months they run it, and payback in a warm state is often 3-5 years.
| Option | Installed cost | Running cost | Warm-up | Where it quits |
|---|---|---|---|---|
| Solar | Highest of the three | Effectively $0 | Days, and only when the sun is out | Shade, too little panel area, or a cold cloudy week |
| Heat pump | About $3,000-$8,000 | About 1/3 of propane, about 1/2 of natural gas | 24-72 hours | Ambient air below about 50 degrees |
| Gas | Lowest of the three | Highest per hour of the three | Hours | The monthly bill the customer did not expect |
Below about 50 degrees ambient a heat pump stops being the answer
A heat pump does not make heat, it moves heat, and it moves it out of the outside air. That is why it is so cheap to run and also why it has a floor: as ambient air drops toward about 50 degrees, the amount of heat available in that air falls away and the unit works harder for less water temperature. Below that line it is still running, still drawing power, and barely gaining. Customers read that as broken. It is not broken, it is out of air to work with.
In Phoenix, Tucson, Orlando, or Houston that floor is a footnote for most of the year, which is why the heat pump is the default recommendation across the Sunbelt. In a market with real winter it is the whole argument, and it is the one place gas genuinely still wins: a gas heater does not care what the air temperature is, and it will take a pool from 62 to 85 degrees in a matter of hours for whatever the therms cost. That is a legitimate answer for a customer who heats four weekends a year and refuses to heat the other 48.
The practical version for the gate: ask how many days a year they actually want to swim. Under about 20, gas is honest. Most of the season, a heat pump. A longer season with no bills, solar. You have just done the whole comparison in three sentences and you did not sell anything.
What a service company should install, sub out, or refuse
Take the plumbing, sub out the electrical, and refuse the gas. Solar panels are the one heating job that sits squarely inside what a route company already does: two tees into the return line, a diverter valve, a sensor, and a run of pipe. If you plumb filters and pumps you can plumb a solar loop. The caveat is the roof - penetrations and flashing are a roofing problem, and an operator who has never set a mount should sub that half and keep the plumbing.
A heat pump is the opposite. The unit sets on a pad and plumbs like a heater, but it typically needs a dedicated 240 volt circuit at 40-60 amps, and on an older house that means a load calculation and sometimes a service upgrade. That is licensed electrical work in essentially every jurisdiction, and it is the half of the job you hand to somebody who does it every day.
Gas is the hard boundary and there is no clever version of it. Gas line sizing, connections, and combustion venting are licensed work with a real consequence attached, and no amount of being handy changes that. Know where the licence boundary sits on gas work in your own state before you are standing in a yard being asked, because the answer you give in the moment is the one the customer remembers.
An operator running 85 pools around Tucson and Oro Valley gets this call on a 16,000 gallon pool: the customer wants to swim in March and October, not in January. South-facing roof, no shade, plenty of area. He quotes the panels and the plumbing himself, prices a heat pump alongside it so the customer can see both, and when they ask about the heat pump he tells them straight that the electrical service work goes to an electrician he already uses. He does not hold that licence and says so. He wins the solar job, keeps the weekly service, and the customer walks away thinking he is the most honest contractor they have met - which cost him nothing except the sentence he was going to have to say eventually anyway.
Set the expectation before the install, not after
Every heating callback in this trade is an expectation problem, not an equipment problem. The customer heard the word heater and pictured a thermostat. Say the warm-up time out loud before they sign: solar works in days and only on sunny ones, a heat pump wants 24-72 hours to bring a pool up and then holds it cheaply, gas moves in hours. Put that sentence in the quote, not just in the conversation, and the November phone call never happens.
The second thing to say is that an uncovered pool gives most of it back overnight. Evaporation is the largest heat loss on a swimming pool by a wide margin, so a solar cover is not an alternative to a heater, it is what keeps the heat the heater already paid for. On solar especially, a customer who will not use a cover is buying a system that spends every morning re-heating what last night took away.
Then write it down. The day a heater goes on a pool, that pool's record changes: there is a new thing on the pad to look at, a new failure mode, and a new reason the pump might be running when you did not expect it. Add it to the pad check at every visit so the next tech on that route is not guessing at equipment nobody told them about.
That is a records habit more than a software one, but it is much easier when the record travels with the pool. Notes and per-visit equipment checks that keep the equipment history for each pool mean the water temperature your tech writes down in March sits next to the one from last March, and a heater that is quietly not keeping up shows itself as a trend instead of a complaint.
FAQ
Frequently asked questions
How long does a solar pool heater take to warm a pool?
Days rather than hours, and only sunny ones. A correctly sized solar system typically adds on the order of 10-15 degrees over an unheated pool, but it gets there gradually, gaining a few degrees across several days of good sun and giving some of it back on a cloudy stretch. There is no boost button. What that means at the gate is that solar is a season-extension purchase, not a weekend purchase: it reliably makes March and October swimmable in a warm climate and it will not make next Saturday swimmable if the forecast is overcast. A cover changes the arithmetic noticeably, because an uncovered pool loses most of the day's gain overnight. Say all of this before the install rather than after the first cool week, because the customer who expected a thermostat is the customer who calls.
Can I install solar panels for a customer without a contractor licence?
It depends entirely on your state and on which half of the job you are doing, so check with your own state licensing board before you quote it. The plumbing side - tying into the return line, setting a diverter valve, running pipe - is usually the closest to what a pool service licence already covers. The roof side is different: mounting panels means penetrations and flashing, which several states treat as roofing or as general contracting, and some set a dollar threshold above which any job needs a licence regardless of trade. The safe pattern most operators land on is to keep the plumbing, sub the roof work to a licensed roofer or solar installer, and put both on one quote so the customer still deals with you. Do not guess at this one, and do not take a neighbour's word for what the rule is in your state.
What do I tell a customer who wants the pool warm this weekend?
Tell them the truth, which is that only gas does that. A gas heater will lift a pool 20 degrees in a matter of hours because it makes heat directly, a heat pump needs roughly 24-72 hours to bring a pool up from cold, and solar works in days and only when the sun cooperates. If the request really is this weekend and it happens four times a year, gas is the honest answer even though it is the most expensive to run, because they are paying for a handful of hours a year rather than a season. If the request is actually a longer season and this weekend was just how they said it, the answer changes completely. Ask how many days a year they want to swim before you quote anything - the number decides the equipment.
Does a solar cover replace a heater or work with one?
It works with one, and on a heated pool it is close to mandatory. Evaporation is the single largest source of heat loss from a swimming pool, so a pool warmed during the day gives most of that gain back overnight if the surface is open. A cover on its own will add a few degrees on a sunny pool in mild weather, which is genuinely useful at the edges of the season, but it is not a heating system and it will not hold a temperature the customer picks. The way to frame it is that the cover protects the heat, whichever system produced it. On solar in particular, a customer who will not handle a cover is buying a system that spends every morning re-heating water that was already warm the evening before, which is exactly the outcome that makes them think the panels do not work.
How much roof or ground area does solar heating need?
Plan on panel area equal to roughly 50-100% of the pool's surface, so a 450 square foot pool wants something like 225-450 square feet of collector. The lower end of that range suits a warm climate and a modest season extension; the upper end is for a cooler market or a customer who wants a real temperature difference. The area has to be unshaded for most of the day and reasonably south-facing, and it can sit on a roof, a garage, a ground rack, or a pergola - the panels do not care, the sun does. Measure it before you talk about price. Half the solar conversations that go nowhere die because nobody checked the roof until after the customer had been quoted, and by then the operator has spent a week and burned the goodwill that would have carried a different recommendation.
Who do I call when a heat pump stops heating but still runs?
Start by checking whether it is actually a fault, because ambient air below about 50 degrees will make a perfectly healthy heat pump run and barely gain. If the air is warm and it is still not heating, the common causes are low water flow, a dirty filter or blocked evaporator coil, or a refrigerant problem. The first two are yours: clean the filter, confirm the baskets are clear, and confirm you have full flow at the pad. If it is still running and not heating with good flow and a clean coil, that is refrigerant work and it needs an EPA certified technician - the same rule that applies to home air conditioning applies here. Note what you found and when you found it, because a heat pump that has quietly slipped over two seasons looks obvious in a run of dated readings and looks like a mystery without one.
