Answer first: solar is one charging source, not a promise of unlimited off-grid power. Calculate daily consumption in watt-hours, decide which season and parking pattern the system must support, map real roof space and shading, and size the array, controller, battery and protection as one system. A headline panel wattage alone cannot answer whether a setup will work in Ireland.
Start with a daily energy budget
Use the method in the leisure battery guide: watts multiplied by hours gives watt-hours. Include refrigeration, lights, water pump, heating controls and fans, device charging, inverter standby and any medical or communications load. Separate essential loads from optional ones.
Then record the charging sources available on a typical day: solar, driving through an appropriate alternator charger, and mains hook-up. Do not count the same energy twice. If the trip includes several parked days, solar may have to cover daily use and replace an earlier battery deficit.
Design for the relevant Irish season
Met Ăireann reports that Ireland normally receives about 1,100 to 1,600 sunshine hours per year, with May and June the sunniest months and December the dullest. Sunshine duration is not the same as peak sun hours used in PV calculations, but the seasonal contrast makes one point clear: a summer result should not be presented as winter capability.
| Use case | Evidence to collect | Fallback to define |
|---|---|---|
| Summer weekends | Measured daily loads and yield from representative trips | Driving or hook-up after poor-weather days |
| Year-round touring | Monthly location-specific solar estimate and winter load profile | Reduced loads plus dependable non-solar charging |
| Long stationary stays | Days of autonomy and recovery time from low state of charge | Hook-up, relocation or generator only where lawful and suitable |
| Storage maintenance | Parasitic loads, shading and charger/battery limits | Scheduled inspection and approved mains charging |
Keep a low-generation case as well as an average. If a safety-critical load cannot tolerate depletion, give it a verified backup rather than relying solely on weather-dependent generation.
Treat roof space and shade as design inputs
Measure clear roof areas around vents, pop-tops, aerials, racks and access routes. Record the vehicleâs height and weight implications, mounting structure and cable-entry position. A panel shaded by a roof light, surfboard or tree can underperform even on a bright day.
Victronâs RV sizing guide distinguishes rigid and flexible panels and explains that wiring in series raises voltage while parallel wiring raises current. It also notes the shading trade-off: shade on one series-connected panel can reduce the stringâs output, while parallel layouts require design for higher current. These are system-design choices, not a reason to copy a generic diagram.
Match the controller to panels and battery
A solar charge controller regulates energy from the array to the battery. Its specification must be checked against the arrayâs open-circuit voltage (Voc), short-circuit current (Isc), wiring arrangement, battery voltage and battery chemistry. Temperature can alter panel voltage, so use the controller makerâs sizing rules and required safety margins.
| Record from the panel | Record from the controller |
|---|---|
| Wattage, Voc, Isc and temperature coefficients | Maximum PV voltage and charge current |
| Number of panels and proposed series/parallel layout | Permitted array power for the battery voltage |
| Connector type, cable route and likely shade | Supported chemistry, settings and temperature sensing |
| Mechanical dimensions, weight and mounting method | Isolation, overcurrent protection and enclosure requirements |
An MPPT controller can efficiently convert a suitable higher panel voltage to battery-charging voltage, but it does not create energy in shade. Verify every limit with the exact data sheets. Never connect panels to an unknown controller or battery configuration.
Write the system brief before buying a kit
- Daily essential and optional energy in Wh, plus peak loads.
- Travel months, locations, stationary days and conservative solar input.
- Battery chemistry, usable capacity, voltage and charging limits.
- Roof drawing with obstacles, shade sources, panel positions and cable entry.
- Panel string figures and controller sizing calculation.
- Isolation, fuses, cable protection, fire-safe routing and mounting design.
- Commissioning tests: polarity, settings, charge current, monitoring and leak check.
- As-built diagram, manuals, settings backup and labelled isolation points.
Roof penetrations can cause water ingress and an unsecured panel can become a road hazard. Electrical faults can overheat wiring or damage batteries. Use competent design and installation, respect the vehicle and equipment manufacturersâ instructions, and have modifications assessed for roadworthiness and insurance implications where relevant. Record the finished work using the vehicle modification document map.
Checked 24 August 2026 against Victron Energyâs RV solar sizing guide and Met Ăireann sunshine guidance. This is a planning framework, not an electrical or structural installation design and not a product endorsement.