| 1. System Size and Energy Planning |
| Common system capacity | Approximately 3–10 kW DC for many detached homes. | Review the last 12 months of electricity bills and identify seasonal peaks. | Allow room for inverter limits, cable sizing, overcurrent protection, and future expansion. | Some jurisdictions limit export capacity or require approval above a specified inverter size. |
| Estimated annual generation | Roughly 900–1,600 kWh per kW per year, depending on climate, orientation, shading, and system losses. | Use a location-specific solar assessment rather than a national average. | Account for temperature, inverter, wiring, mismatch, dirt, snow, and shading losses. | Local solar-access rules, weather conditions, and utility export limits may affect the final estimate. |
| Roof area | Allow approximately 6–10 m² per kW of usable roof area, including practical spacing and access. | Measure only unobstructed areas that are suitable for mounting. | Keep required clearances from roof edges, ridges, valleys, vents, skylights, and emergency access paths. | Setback distances vary by building code, fire authority, roof type, and local permit requirements. |
| Panel orientation and tilt | Unshaded surfaces generally produce the best results; exact optimum depends on latitude and roof geometry. | Compare annual production for each roof plane, not just compass direction. | Use suitable mounting angles, wind-rated fixings, waterproof penetrations, and corrosion-resistant hardware. | Historic districts, homeowners’ associations, and planning authorities may regulate visible equipment. |
| Battery storage | Common residential storage ranges from approximately 5–20 kWh usable capacity. | Size the battery using evening demand, backup priorities, solar production, and required autonomy. | Provide approved battery enclosures, ventilation or spacing where required, isolation, protection, and safe access. | Battery location, indoor installation, fire separation, and emergency-response requirements vary by jurisdiction. |
| 2. Electrical and Structural Installation Requirements |
| Main service capacity | Existing residential services may be approximately 60–200 A, depending on the country and property. | Check the main service rating, available breaker space, load calculation, and existing electrical condition. | Do not exceed service, busbar, conductor, or protection ratings. Upgrade equipment if the calculated load requires it. | Electrical authorities may require a service upgrade, dedicated disconnect, inspection, or utility witness test. |
| Roof structural capacity | PV equipment commonly adds approximately 10–25 kg/m², depending on modules and mounting. | Inspect rafters, trusses, roof age, corrosion, water damage, and snow or wind exposure. | Mounting points must transfer dead, uplift, sliding, and wind loads into suitable structural members. | Structural calculations or certification may be required in high-wind, high-snow, seismic, or coastal areas. |
| Roof condition | Solar equipment is typically intended for a long service life, so the roof should have adequate remaining life. | Repair or replace an aging roof before installing the array whenever practical. | Use compatible flashing and avoid unnecessary penetrations. Preserve drainage and roof warranty conditions. | Building inspectors may require documentation for roof coverings, waterproofing, and attachment methods. |
| DC and AC disconnects | Disconnecting means are normally required for safe isolation and maintenance. | Confirm the equipment layout and whether emergency responders can access the required isolation points. | Label circuits clearly, protect cables from physical damage, and install weather-resistant enclosures outdoors. | Disconnect location, visibility, labeling, and rapid-shutdown requirements depend on the applicable electrical code. |
| Grounding and bonding | Metal frames, mounting rails, enclosures, and exposed conductive parts generally require bonding or grounding as applicable. | Verify continuity, conductor sizing, corrosion compatibility, and connection security. | Follow the applicable wiring code and manufacturer installation instructions; do not rely on painted or loose metal contact. | Grounding electrode and bonding methods differ between national and local electrical regulations. |
| Surge and lightning protection | Protection needs increase in areas with frequent lightning, long cable runs, or overhead electrical infrastructure. | Assess lightning exposure, existing surge protection, cable routes, and the building’s earthing system. | Use appropriately rated surge protective devices where required and coordinate them with overcurrent protection. | Local code, risk assessment, and utility requirements determine whether additional surge or lightning protection is mandatory. |
| 3. Safety Standards and Equipment Selection |
| PV modules | Modern residential modules commonly have approximately 18–23% efficiency. | Compare electrical ratings, temperature coefficients, dimensions, warranty terms, and fire classification. | Use modules tested and certified for the installation market and mounting environment. | Certification marks and accepted test standards vary by country; confirm acceptance before purchase. |
| Inverter selection | Typical residential inverters are approximately 3–10 kW AC, with a DC-to-AC ratio often around 1.1–1.4. | Match voltage, current, MPPT range, phase configuration, backup requirements, and grid settings. | Use certified grid-interactive equipment with anti-islanding protection and correctly rated protection devices. | Utilities may require specific grid-support functions, approved equipment lists, or commissioning settings. |
| Applicable technical standards | Common international references include PV array design, low-voltage installation, inverter safety, and module safety standards. | Ask the installer to identify the exact edition and national adoption of each applicable standard. | Design and installation should follow the locally adopted electrical, fire, building, and product-safety codes. | Examples may include IEC 60364-7-712, IEC 62548, IEC 62109, IEC 61730, or equivalent national standards. |
| Fire safety and access | Roof access paths and clearances are often required around edges, ridges, equipment, and emergency routes. | Confirm the local fire authority’s requirements before finalizing the panel layout. | Keep escape routes clear, label energy storage equipment, and avoid blocking vents or emergency access. | Fire setbacks and rapid-shutdown rules can differ substantially between municipalities and building types. |
| Monitoring and shutdown | Most current systems can provide production, consumption, fault, and battery-state information. | Choose monitoring that remains available during internet outages and provides clear fault notifications. | Ensure shutdown controls are accessible, labeled, tested, and included in handover documentation. | Some jurisdictions require rapid shutdown or other emergency isolation functions for rooftop arrays. |
| 4. Permits, Grid Connection, and Handover |
| Planning permission | Many ordinary rooftop installations may qualify for simplified approval, but this is not universal. | Check planning restrictions before signing a fixed design or ordering equipment. | Prepare roof plans, array layouts, equipment locations, structural details, and visual-impact information if requested. | Planning controls may be stricter for historic buildings, conservation areas, protected landscapes, and multifamily housing. |
| Building and electrical permits | Permits or notifications are commonly required for rooftop PV, electrical modifications, or battery storage. | Confirm who applies for permits and who schedules inspections. | Installation should be completed by appropriately licensed or qualified personnel where required. | Permit thresholds, inspection stages, and documentation requirements are set locally. |
| Grid interconnection | Approval may be required before parallel operation with the public grid. | Submit single-line diagrams, inverter details, export limits, protection settings, and site information when requested. | Do not energize a grid-connected system until utility and inspection requirements are satisfied. | Export caps, application fees, smart-meter changes, and approval timelines vary by utility and region. |
| System documentation | A complete handover package should include equipment data, drawings, test results, and maintenance information. | Require documentation before making the final payment. | Keep the single-line diagram, operating instructions, shutdown procedure, warranties, inspection records, and serial-number schedule. | Some authorities require certificates of compliance or as-built drawings for final approval. |
| Installer quality checks | Important checks include polarity, insulation resistance, protective-conductor continuity, torque, labeling, and functional testing. | Request test records and confirm that defects are corrected before handover. | Use calibrated test equipment and follow the applicable commissioning procedure. | Inspection bodies or utilities may specify additional tests for batteries, export control, or backup systems. |
| 5. Practical Selection Guide |
| Best choice for low daytime usage | Moderate PV capacity with load shifting or appropriately sized storage. | Compare the cost of storage with the value of self-consumed solar energy. | Ensure battery operating temperature, ventilation, isolation, and fire requirements are satisfied. | Check whether storage receives separate permits, incentives, or export restrictions. |
| Best choice for high daytime usage | A system sized to offset daytime consumption may achieve a higher self-consumption rate without a large battery. | Review hourly or half-hourly consumption data where available. | Confirm that simultaneous loads, inverter capacity, and service equipment are suitable. | Utility export rules may still limit system size even when onsite demand is high. |
| Best choice for backup power | Prioritize essential circuits rather than attempting to back up the entire house. | List critical loads such as refrigeration, communications, lighting, heating controls, or medical equipment. | Use approved transfer equipment and ensure the backup system cannot energize the utility network during an outage. | Backup operation may require additional permits, utility notification, and specific isolation equipment. |
| Overall decision rule | Choose the system that meets energy, roof, electrical, safety, and regulatory requirements together. | Obtain at least one site-specific design with a production estimate and electrical single-line diagram. | Reject designs that omit structural review, protection details, shutdown procedures, or commissioning tests. | Verify all requirements with the local building authority, electrical inspector, fire authority, and utility before installation. |
