To provide an independent source of power for a home - in case of blackouts - some form of battery storage is required. This adds considerable cost but does mean you have the best of both worlds: solar power earning you money when the sun shines, and a reliable battery backup for when the grid fails. How much power a battery backup system can supply is determined by the size of the battery bank and thus the cost of the system will increase proportionally.

Option 1: 1.4kW PV solar system with 24V 400Ah (@10hr rate) sealed battery bank

This system (in an sunny location in Melbourne) will produce about 5.25kWh/day (annual average) but in summer, when blackouts are more prevalent will produce about 7.4kWh/day. The battery storage if taken to a depth of discharge of 70% will be able to deliver 6.7kWh of energy - enough to run a typical refrigerator, deep freeze, some lights and a modest TV and radio for a day. If the following day is sunny then the batteries will charge up again and be able to deliver the same amount of power again the following day. The battery storage and special interactive inverter will add about $10,000 to the basic PV grid-connect system.

Option 2: 1kW PV solar system with 24V 400Ah (@10hr rate) sealed battery bank

This system (in an sunny location in Melbourne) will produce about 3.75kWh/day (annual average) but in summer, when blackouts are more prevalent will produce about 5.3kWh/day. The battery storage if taken to a depth of discharge of 70% will be able to deliver 6.7kWh of energy - enough to run a typical refrigerator, some lights and a modest TV and radio for a day. If the following day is sunny then the batteries will charge up again and be able to deliver about 4.2kWh of power again the following day. The battery storage and special interactive inverter will add about $10,000 to the basic PV grid-connect system.

Option 3: 2.1kW PV solar power system with 24V 600Ah (@10hr rate) sealed battery bank

This system (in an sunny location in Melbourne) will produce about 7.5kWh/day (annual average) but in summer, when blackouts are more prevalent will produce about 10.6kWh/day. The battery storage if taken to a depth of discharge of 70% will be able to deliver 10kWh of energy - enough to run a large refrigerator, deep freeze, many lights and a TV and radio for a day. If the following day is sunny then the batteries will charge up again and be able to deliver the same amount of power again the following day. The battery storage and special interactive inverter will add about $12,000 to the basic PV grid-connect system.

Photo of 770Ah (@100hr) 24V sealed battery bank (with 3500W inverter and MPPT charge controller above)