Off-grid solar supplies loads that do not rely on the public grid. It must provide enough energy and power during difficult periods, with clearly defined operating limits. Adding a battery to a grid-connected system does not automatically make it off-grid capable.
Design in the right order
- Record appliances, operating hours and seasonal demand.
- Separate critical loads from loads that can move to another time.
- Estimate monthly generation and examine the difficult season.
- Select batteries, inverter and any reserve source as one system.
Annual generation can exceed annual demand while the installation still runs short in winter. An annual average cannot demonstrate continuous autonomy.
A hypothetical energy example
If critical loads need 6 kWh/day, two days without useful generation require 12 kWh delivered energy. Nominal battery capacity must account for usable fraction, losses and reserve. This calculation alone does not size the array: it must also recharge storage while continuing to serve operating loads after a low-sun period.
Consider recovery time explicitly. A system that survives two difficult days but takes several clear days to replenish its reserve may be vulnerable to the next cloudy period.
Inverter power limits simultaneous use
Continuous power, temporary overload and motor-start capability are different limits. A heater, pump and oven can exhaust the power budget long before the battery runs out of energy. Load scheduling is part of the design, not merely a user preference added after installation.
Reserve sources and electrical protection
Where the required availability cannot reasonably be supported by solar and batteries alone, a compatible reserve source may be assessed. Switching, earthing and protection require professional design. An autonomous installation must not be improvised into a parallel grid connection without the appropriate architecture and checks.
Handover and future changes
Request an allowed-load schedule, minimum state-of-charge settings, alarm behaviour, maintenance instructions and a plan for extended cloudy weather. Adding water heating, an electric vehicle or another pump can materially change the design assumptions and should trigger reassessment.
The published 10 kW off-grid installation in Zaros is a real reference. Explore our off-grid service and use PVGIS as a source of solar-resource data, not a substitute for complete electrical engineering.
Autonomy is an operating policy
An off-grid system has no grid to cover an unlimited forecasting error. The design should define what happens at low battery charge: which loads are disconnected, whether a secondary source exists and how it starts. Even correctly sized equipment needs maintenance and monitoring.
Ask the installer for an operating diagram and concise user instructions covering charge status, operating limits, alarms, safe restart and support contacts. The handover should be more than a list of devices. For a residence, see the off-grid home guide.
Discuss your installation
Send your location, bills, operating hours and available roof space for an individual assessment.
Request an assessment