| Reduce daytime electricity bills |
Approximately 8–15 kWh per day, with major loads operating between 9:00 and 17:00 |
Approximately 3–5 kW of solar capacity, depending on local sunlight and annual consumption |
Grid-connected string inverter; a DC-to-AC ratio of approximately 1.1–1.3 can improve morning and afternoon production |
Usually optional; consider 5–10 kWh of usable storage if evening consumption is significant |
Unshaded roof or ground area with approximately 15°–40° of tilt and good access for maintenance |
Prioritize direct use of solar power. Shift water heating, washing, and charging loads to daylight hours where possible. |
| Maximize annual bill savings |
Approximately 15–30 kWh per day with moderate or high annual consumption |
Approximately 5–10 kW, subject to roof area, electrical limits, and local grid rules |
Three-phase or single-phase inverter selected according to the property supply; multiple MPPT inputs are useful for different roof orientations |
Approximately 10–20 kWh of usable storage when export rates are low or evening demand is high |
Minimal shading during the main solar window, preferably from 9:00 to 15:00 throughout the year |
Compare annual generation with annual consumption rather than sizing only from the highest monthly bill. Include seasonal demand changes. |
| Increase energy independence |
Approximately 15–35 kWh per day, including evening and overnight loads |
Approximately 6–12 kW, often larger than a bill-reduction system to support battery charging |
Hybrid inverter with grid connection, battery charging capability, and managed backup output |
Approximately 15–30 kWh of usable storage; reserve 10%–20% for emergency operation |
Large, mostly unshaded array area with reliable solar exposure during winter months |
Battery capacity must be checked against both daily energy demand and peak power. High-power appliances may require load management. |
| Provide backup during grid outages |
Critical loads commonly include refrigeration, lighting, communications, internet equipment, and selected medical devices |
Approximately 3–8 kW, depending on the critical-load demand and desired recharge speed |
Hybrid or battery-based inverter with a dedicated backup output and automatic transfer capability |
Approximately 5–15 kWh of usable storage for essential loads; more may be needed for multi-day outages |
Accessible equipment location, protected battery environment, and adequate ventilation and clearance |
Separate essential circuits from high-load circuits. Verify starting currents for pumps, compressors, and motors. |
| Support electric vehicle charging |
Vehicle energy use may add approximately 5–15 kWh per 100 km driven |
Add approximately 2–5 kW of PV capacity for moderate weekly driving, depending on mileage and charging schedule |
Inverter and charger should be coordinated with the site's service capacity and available daytime solar power |
Optional; storage can allow charging after sunset but may increase system cost and conversion losses |
Available roof area, sufficient electrical service, and a practical cable route to the parking location |
Solar-aware charging can reduce grid purchases. Confirm whether the charger can dynamically follow surplus PV output. |
| Operate in a remote or weak-grid location |
Approximately 5–25 kWh per day, depending on water pumping, refrigeration, communications, and tools |
Approximately 4–15 kW, sized for both average energy use and seasonal solar conditions |
Off-grid or hybrid inverter with generator integration, battery charging controls, and sufficient surge capacity |
Typically 1–3 days of usable storage; lithium-based systems commonly use an 80%–90% maximum depth of discharge |
Unshaded ground or roof area with secure equipment housing and all-season maintenance access |
Include a backup generator or other source when prolonged cloudy periods are possible. Design for the lowest-sun season. |
| Use a small apartment or limited roof area |
Approximately 4–10 kWh per day, often with limited control over major loads |
Approximately 1–3 kW, depending on available roof, balcony, or shared-array capacity |
Microinverters or module-level power electronics can help where shading or multiple orientations exist |
Optional; approximately 3–8 kWh of usable storage may cover evening essentials |
Confirm structural approval, shading from nearby buildings, orientation, and permission to connect to the electrical system |
Limited area makes accurate shading analysis important. Check building rules, fire access, metering, and grid-connection requirements. |
| Optimize performance on a partially shaded roof |
Any household or small-business load profile |
Size according to annual energy demand, but expect lower output than an equivalent unshaded array |
Use multiple MPPT channels, module-level power electronics, or separate array sections for different roof planes |
Storage does not remove shading losses; size it from actual load timing and backup requirements |
Detailed shade assessment from nearby trees, chimneys, parapets, and neighboring buildings |
Even brief shading can affect string output. Trim or remove avoidable shade where practical before final system sizing. |
Stuart Solar
