Going off-grid

To determine your payback period on a solar PV/battery system that can operate fully off-grid, here are some things you should consider:

• The purchase price
• The number of solar panels you need
• Usable battery capacity needed
• System maintenance costs
• The loss of a feed-in tariff
• Losing the opportunity to export electricity to the grid for payment via a Virtual Power Plant program or similar arrangement
• The future price of electricity (will it go up or down, and by how much?)
• Your electricity usage – both your daily peak demand and your total use in an average week.

You should also consider if you’ll stay in your home long enough to recover your costs.

Discuss your ideas with a number of solar PV/battery suppliers who understand off-grid systems to see what options they suggest.

Considering your daily electricity use, is there enough of your roof in the sun and otherwise suitable for solar panels for the number of panels you’ll need? If you don’t have enough suitable roof space, you may need to mount panels on your shed or even on the ground. This would increase your set-up costs and could have visual impacts and other downsides.

Having an off-grid electricity system means thinking about the right size generation and storage to get you through your peak daily needs and a run of cloudy days. Your solar PV/battery system won’t supply power if:

• The battery has been fully used and the sun is not out
• There is a system fault or breakage
• It is undergoing scheduled maintenance.

If you can’t do without power at those times, you’ll need a back-up generator to meet your basic electricity needs. A generator must be housed somewhere safe with appropriate ventilation and not cause a disturbance (e.g. noise and smell). Generators will run best when maintained regularly and refuelled. Read more about generator safety and use.

An alternative is to consider how an electric vehicle (EV) with Vehicle-to-Load or Vehicle-to-Home capability could fulfil the role of a back-up generator and as an extension to your stationary battery system. See more details at No. 9.

Your electricity use varies greatly within a day, with regular high spikes of demand for very short times. Air conditioners and pool pumps, for example, can create short bursts of high demand when starting.

An off-grid system's inverter must be able to supply this high start-up power or the appliance may not start properly. Kettles, toasters and hair dryers, for example, can also create spikes.

If your inverter cannot supply these high spikes in demand, you may have to give up some non-essential appliances, or use them less and not at the same time. Alternatively, you may have to install a larger solar PV/battery system at a higher cost.

Going off-grid usually requires some lifestyle changes, depending on the type of appliances you have, the capacities of your solar PV and battery systems, and your electricity demand.

Energy-saving habits and energy efficient appliances will help to prevent your system cutting out or you not having enough power to run your home. Also, you can consider the impacts of:

• Having house guests
• A particularly cold winter or hot summer
• Hosting a party.

Would your system cope?

All battery types have risks including explosion, fire and chemical leakage. To keep you, your family and your neighbours safe, ensure your batteries are:

• Installed correctly
• Sited safely, in relation to living spaces, exit paths and potential damage to your home and car
• Regularly maintained.

There are regulations governing the siting of batteries that could add to your purchase costs. Read more on the Battery Safety Guide website.

Solar panels generally last longer than inverters and battery management systems. This means you may need to replace inverters and other components at least once during the life of your solar panels. You may even have to replace your panels when you replace your inverter.

If your system breaks down, it could be quite costly to fix.

You may also have to pay someone to clean your panels, check your system (ideally annually) and service your generator.

When you go off the grid, maintaining your power supply becomes your responsibility. Regular services by an electrical professional are essential.

Minor issues could be inconvenient and result in you using your backup generator for many days. Some important questions for a potential supplier or installer include:

• Who do I call for help?
• What are the warranty periods for various components?
• How long before a technician could be here?
• How long might it take spare parts to come?

If you have an electric vehicle (EV) or are considering buying one, charging it creates a high electricity demand (kW) and consumption (kWh). Meeting that extra demand may add a lot to your solar PV/battery set-up costs and the roof space required for panels. The average EV draws around 18kWh of charge to travel 100km¹.

However, an EV may provide benefits to those living off-grid. If your EV has Vehicle-to-Load functionality, and your PV and battery system cannot meet your needs at times, you could plug some appliances (e.g. fridge, microwave, phone chargers) into your EV temporarily.

If you have an EV that can support a Vehicle-to-Home arrangement, and you invest in the relevant bidirectional EV charger and electrical wiring, you could power one or more of your home’s electrical circuits from your EV, until your PV and battery system is operating again.

An off-grid home may attract some potential buyers and deter others, so if going off-grid is appealing to you, consider the following:

• The potential buyer pool could be smaller when you come to sell your home
• Even if a buyer is prepared to pay more for an off-grid house, that amount may be less than the total amount of the payback you expected
• As well, check with your home insurer to ensure your home remains suitably insured.

Also, it’s a good idea to check any local council restrictions or estate covenants. These can include restrictions on solar panels on the front of houses, where the batteries are housed and the use of petrol/diesel generators.