What’s a partial off-grid solar plus storage system?

Solar Choice
Going partially off the grid is a smart alternative for homes who want to become completely energy self-sufficient. A partial off-grid solar system is one that runs a few essential electrical loads – for example, the refrigerator, lights and television – on a separate electrical circuit that has no physical connection to the grid mains. The rest of the devices in the home run using grid power and/or a grid-connect solar system.

Why go partially off-grid?

Going completely off-grid requires extra-special dedication

Plenty of Australian homeowners dream about going off the grid with solar panels and home battery storage. But for the average, grid-connected Aussie home – which consumes between 20 and 30 kilowatt-hours (kWh) of energy per day – installing a system large enough to keep the lights (and everything else) on throughout the year just isn’t worth it.
If they rely solely on solar and batteries, such a home would need enough capacity to carry them through 3-4 days of gloomy weather. Right away, this is a significant financial commitment, especially when compared to the relative affordability of grid-connected solar systems, whose prices sit at historic lows in Australia.
Besides the up-front cost, one of the main hurdles on the path to getting off the grid is reducing energy consumption in the first place; in order to avoid unnecessary expenditures on system capacity, the home should work on getting its consumption levels as low as possible. This will be a significant hurdle to those who are not completely dedicated to the off-grid endeavour: the occupants of a home have their habits (which can be hard to change), and there’s only so far a home may be willing to go (because of budgetary or other restraints) to replace all their inefficient devices with efficient ones.
As a result, it can be difficult for a home to reduce its energy consumption dramatically without causing inconvenience or discomfort for at least one of the occupants (e.g. the one who keeps the electric hot water heater on its toes with their marathon showers). Another hurdle is occasional usage spikes – when multiple devices (vacuum, washing machine, dishwasher) are all turned on at once. While the grid can handle such events with ease, a home relying on batteries and solar could quite easily trip the switch unless the system has been specifically designed for these occasions (which a good system should be).
So in summary, for those who just want to go about their daily lives without thinking too much about how they are using energy throughout the day, completely disconnecting from the grid may not be particularly appealing. Installing a partial off-grid system might be a good option instead.

Partial off-grid living vs full off-grid living

For most homes, electricity usage patterns for certain things is completely regular and predictable. Refrigerators, lighting and chargers for smartphones & laptops, for example, all consume minimal amounts of electricity at a given time, making them ‘low risk’ devices to target for removal from a grid-connected electricity circuit. Imagine if you could use them 24/7 knowing that they’re running on your home-grown solar energy – making you largely independent of the grid, but also resting comfortably with grid access whenever you need it for the rest of your home. This is the promise of a partial off-grid solar system.

The main benefits of a partial off-grid solar-plus-storage setup are:

• Smaller up-front costs compared to taking your home fully off the grid (less money needs to be invested in surplus solar & battery capacity)
• Preserve existing solar feed-in tariff entitlements (expanding an existing grid-connected solar system could void eligibility for a feed-in tariff you currently receive – check with your installer for details)
• Greater level of energy independence for the home (relying on the grid only for heavier & more unpredictable loads)
• No need to worry about battery state of charge (the system will be sized to meet only predictable loads)
• Your essential loads stay on even when the grid is down (you may also plug additional devices into your off-grid circuit)
• Grid power available when needed (it’s also possible to have a grid-connected solar system in addition to the off-grid system)
• Save money on your power bills – you will never see a bill for the energy supplied to you by your solar + batteries

The main disadvantages of a partial off-grid system:

• You still have an electricity bill (with a completely off-grid system, you’d have no energy bill)
• You’ll still pay daily ‘supply charges’ (as long as you have a grid connection, you’ll have to pay flat supply charges regardless of whether you purchase any energy from the grid on a given day)

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Source: SolarChoice. Reproduced with permission.