Owners usually call saying the batteries still go flat overnight even though the panels sit in full sun all day. Our technicians start at the battery bay rather than the roof, because a bank that will not hold overnight has a draw problem or a tired battery problem that no amount of solar will fix. The roof survey comes second. We inspect the Dicor self-leveling lap sealant around the vents and antenna base, press the decking near the seams for soft spots, and note where a typical campsite drops shade across the panel area. Every mounting foot is a new penetration, and a foot bedded in butyl tape and capped with fresh self-leveling sealant stays dry for years while one sealed with the wrong product wicks water straight into the plywood.
Panel nameplate wattage is measured at Standard Test Conditions: 1000 watts per square meter of irradiance and a cell temperature of 25 C. A silicon module loses roughly 0.35 to 0.40 percent of rated power for every degree above 25 C, and a dark roof in July puts cells far above that. That is a 13 to 18 percent haircut at the exact hour the sun sits highest. Afternoon cloud build-up takes another share. A 400 watt array on a Florida roof therefore makes something like 1.2 to 1.8 kilowatt hours on a clear day here, and much less under a storm cell. That matters for expectations. Rooftop solar keeps a residential fridge and the 12 volt loads alive, but a Dometic Penguin II 13,500 BTU air conditioner pulls roughly 1,300 to 1,500 watts continuously, which is a large battery bank and a dedicated inverter decision rather than a panel decision.
A PWM controller ties the array almost directly to the battery and drags panel voltage down to battery voltage. An MPPT controller converts instead, holding the panel at its maximum power point and turning the surplus voltage into extra charging current. The gain is real, but it is not universal. With true 12 volt nominal panels, the 36 cell modules built for 12 volt systems, where Vmp sits near 18 volts, a PWM unit such as a Go Power GP-PWM-30-DL wastes only the gap between 18 volts and roughly 14 volts of charging. On a single 100 or 200 watt panel that difference rarely repays the upgrade. MPPT earns its price with 60 and 72 cell residential panels, where Vmp sits near 30 to 40 volts and PWM would discard more than half the harvest. A Victron SmartSolar MPPT 100/30 accepts up to 100 volts of PV input and needs array voltage at least 5 volts above battery voltage to start.
Wiring panels in series adds their voltages and keeps current low, which is why a long roof to controller run favors series. The catch is that a series string carries one current, so the shaded panel sets the current for every panel behind it. One live oak limb or palm frond across a single module pulls the whole string down, and the bypass diodes in the junction box only route around a shaded substring. Parallel wiring gives each panel its own path, so a shaded module drops out of the total while the others keep producing. The price is current: three 200 watt panels in parallel push roughly 30 amps up the run, so conductors get heavier and the array needs branch fusing in a combiner box once you exceed two parallel strings. Our technicians choose from where you actually park. Shaded Florida sites favor parallel or series-parallel pairs, while open boondocking roofs favor series for the voltage headroom and thinner cable.
Voltage drop is where an undersized install quietly loses output. Ten AWG copper runs about 1 ohm per 1,000 feet, so a 20 foot roof to controller run is 40 feet of conductor there and back, near 0.04 ohms, and 20 amps through it drops about 0.8 volts. On a 14 volt charging circuit that is a real loss, and it is why we size the controller to battery leg in 6 or 4 AWG through a Blue Sea Systems MRBF terminal fuse instead of reusing thin factory prewire. Blown controller fuses trace to four causes: reversed polarity at the battery, a fuse rated under the controller output, a chafed positive conductor at the roof entry gland, or connecting PV before the battery, which the Victron SmartSolar manuals warn against directly. Our technicians confirm polarity and continuity with a Klein Tools MM600 and read real charge current with a Fluke 376 DC clamp meter before any part is replaced.
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Call 888-759-1438Yes, and it is often the cheapest real gain available. Most factory prewire is thin 10 AWG run a long way, so we measure actual drop under load first, then upsize the controller to battery leg to 6 or 4 AWG and re-terminate the MC4 connectors with a proper MC4 crimping tool. We also add or correct fusing at the battery end, since many factory runs have none at all.
Yes. Our technicians measure the usable roof area around the vents, fan and antenna, check the existing battery bank and its charge source, and tell you what array that roof can genuinely carry. That conversation usually changes the parts list, because roof area, controller input limits and the charge acceptance rate of the bank decide the size of an array far more often than budget does. It costs less to hear that before the panels arrive than after.
A repeatedly blowing fuse is a symptom, not the fault. The four we find most are reversed polarity at the battery terminals, a fuse rated below the controller output current, a positive conductor chafed against the metal roof entry gland, and connecting the PV array before the battery on startup. Left alone, the next thing to fail is usually the controller itself, which costs far more than the diagnosis.
Almost never on panels alone. A Dometic Penguin II 13,500 BTU unit pulls roughly 1,300 to 1,500 watts continuously, while a 400 watt Florida array makes something like 1.2 to 1.8 kilowatt hours across an entire day. Running air conditioning from stored power is a battery bank and inverter question, not a panel question.
No. An MPPT controller such as a Victron SmartSolar unit carries charge profiles for flooded, AGM and LiFePO4 banks, so solar works with the bank you already own. Lithium is a separate decision driven by usable capacity and charge acceptance rate, not by adding panels. The profile is set once in VictronConnect over VE.Direct for whichever bank you are running today.
A two panel array with a controller and a fused battery run is usually most of a day once the roof is prepped, and the prep is the variable. If the existing lap sealant is chalked and splitting, that gets addressed before anything is bonded down, because sealing a new mounting foot onto failing sealant just buys a leak. Longer cable runs and a combiner box add time.
Every figure on this page comes from a manufacturer document or a standards body, not from another repair site. Here is where each one comes from.
| Item | Price | What it covers |
|---|---|---|
| Service call | $299 | Includes the trip out to your RV and the first hour on site |
| Work past the first hour | Quoted after diagnosis | We tell you what it will take before we carry on |
| Parts | Quoted per job | Special-order parts may need a deposit before we order them |
| Written estimate | No charge | You approve the estimate before any work starts |
The service call covers the trip out to your RV and the first hour on site. Anything beyond that depends on what we find, and we quote it and get your approval before carrying on.
The price ranges on this page come from our own recent jobs across Florida, not from an industry average. What you pay depends on the rig, the parts it needs and what we find on site, so we give you a written estimate before any work begins and you approve it first.