About Off-Grid

Why go Off-grid? #

Avoid charges: You can avoid fixed and ongoing grid electricity charges.

Economic for the network: In some remote locations, networks may find it more economic to pay households to install solar and a battery than to maintain or replace long power lines.

Avoid outages: By going off grid you can avoid the risk of grid outages.

Location limitations: A new, rural grid connection would be expensive and going off grid would be a cheaper alternative.

Microgrids: Groups of homes or businesses may benefit from forming their own small grid that is not connected to the main grid

Things to Consider:

High installation costs: Installing an off-grid system is considerably more expensive than one that is connected to the grid. For an average Australian household, an off-grid hybrid power system may cost $25,000 to $75,000 upfront. A hybrid system consists of solar, hybrid inverter and battery with a generator backup.

Export restrictions: You won’t be able to export your excess electricity from your rooftop solar or solar battery back to the grid.

Responsibility: You are responsible for your own security of supply and its costs.

The future: When selling your home in the future, buyers may have energy needs that are different to yours. Reconnecting to the grid can be costly.

Generator backup: By going off grid you may be reliant on a diesel or petrol generator to provide backup power.

Understanding your energy usage #

When considering a solar system with a battery, you have to understand how much energy you use and when you use it.

When considering an off-grid solar system, you have to understand how much energy you may use and how it may fluctuate during the night or when there is change in seasons.

This is to:

  • Avoid using power when it is most expensive
  • To find the right battery capacity by knowing when you may use more electricity and accounting for inverter inefficiencies, voltage drop and other losses.

Typically, the appliances using the most electricity are hot water systems, fridges and heating / cooling systems. Most homes use the most power in the early morning as well as late afternoon and the evening.

Calculate how much energy a solar panel can generate and what it can power #

How Off-grid works

For an off-grid solar system, you would need 4 components; the standard solar panels and inverter (an off-grid variant), along with; charge controller and battery bank. A battery bank is used to store energy generated or taken from the grid; a charge controller is also installed to prevent batteries from overcharging. 

The only reasons to want to go off-grid are: you live in a rural area without connectivity to the grid, want to be completely independent from the grid or live in a mobile home such as a caravan or a boat. If your goal is to save money, going off-grid would not be for you; due to the high upfront cost of battery systems despite government subsidiary. It is much better to stay on-grid where you have access to a feed-in tariff and convenient grid-connectivity.

A grid-connected home solar battery system can provide many of the benefits of going off-grid, including a mostly clean and renewable power supply, while continuing to provide access to reliable grid electricity when needed. Sizing your home solar battery system to supply enough power 80 to 90 percent of the time is more cost-effective than going fully off-grid. It means you can export excess solar energy to the grid and use the battery in an efficient way. We highly recommend you to only consider off-grid if you were living in a remote location or live in a mobile home.

Planning for a battery-system #

This figure compares the energy usage during different time of the day, comparing between having batteries or no batteries.

Different Types of Batteries #

Lithium-Ion: Lithium-ion batteries are small and light and have relatively long lifespans. They are usually used for on-grid systems, as they have seen a steady decrease in cost in recent years.

Lead-acid: Lead-acid batteries are simple, reliable and cheap. They however, have difficulty being fully-charged and are very heavy with a low cycle-life. They also require regular maintenance and must be kept in a ventilated environment.

Other types: Other main type of battery used is ‘flow’ batteries, which use liquids to store energy. They are known for being easy to maintain, relatively sae and ability to store charge for long periods. They have a low energy density compared to lithium ion.

Useable capacity

This is the amount of a battery’s total or rated capacity that is available for regular use without overly affecting its lifespan. For example, a battery may have a rated capacity of 12 kWh, but its recommended useable capacity is only 10 kWh. If information is not available, you should assume that around 10% of the total capacity should not be used on a regular basis. This needs to be considered when comparing batteries.

Size of battery #

Choosing the right sized battery storage for your needs is dependent on the size of your solar PV system. You have to account for how much energy you use, especially during peak periods. You may also consider having power backup during blackouts. As having a battery system has high upfront costs, consider getting one that fits with your budget.

Choosing a battery

To lower your power bill as much as possible, it is advised to buy a battery you will regularly charge and discharge to the recommended levels. This means you would need to generate excess solar during the day, to charge the battery and have enough stored for when you are not generating solar for discharging.

Be careful to not over-use a battery as this will shorten its lifespan. It is recommended to charge and discharge no more than 2-3 times a day. You are able to control how much it can charge and discharge in the energy management system.

Things to consider for battery sizing

To make the most out of your solar. Calculate how much excess solar energy you will have during the day. Just subtract the amount of energy consumed during energy generation. It is recommended you store enough energy that will be sufficient for use during the evening peak times, when there is no sunlight and you won’t generate any solar power.

For example:

If you have a 6.6 kW system, it should generate 31.94 kW of energy a day. If you use 20 kW of energy during sunlight hours, you will have 11.94 kW remaining which you can use to charge the battery.

To have backup for multi-day outages. If you are in an area where you would expect to have frequent power outages, it’s best that your battery can store enough energy to cover several days of energy use. If you are unable to generate enough solar to charge, you may need an on-site diesel generator to cover the remaining energy you may use.  This is commonly done in off-grid systems, you would need a special inverter and isolation switch.

Backup power capability

A standard hybrid system would not work during a power outage. For backup power you would need an isolation switch. This would incur additional charges. This is commonly used in off-grid systems but it would be useful if you live in area with frequent black-outs, or want to prepare in the off-chance that a black-out would occur.

Future-proofing #

Timing. Battery systems have a high upfront cost and are expensive. The best way to make the most of your investment is to only buy a battery when you are confident your pay-back is within your warranty period. Prices are falling steadily; this could mean you could wait until it falls within your budget and you would have a shorter pay-back period.

Solar first, battery second

It is recommended to install a solar PV system first, and worry about battery systems later. As battery systems have a high upfront-cost, it’s best to consider a battery a few years down the road of your solar journey.

To prepare for installing a battery-system, you need to make sure your inverter is ‘battery-ready’. Battery systems only work with a hybrid inverter or any inverter that has battery capability. You also have the option to AC-couple the battery. AC-coupled batteries are generally less efficient (90%) and cannot function as a back-up supply, they also are not designed for off-grid systems and may pose problems for that purpose.

Start small. Batteries are modular and thus you can always add more units in the future. Ensure your inverter capacity matches your needs. Some batteries include an inverter in each module.

Calculating Pay-back period for battery systems #

Calculating pay-back period for battery systems can be tricky. This is because they may not pay for itself back before the warranty period expires. To estimate the pay-back period, divide the upfront system costs by the projected annual savings.

Factors to consider

  • Take into account your energy-usage patterns. This affects the level of discharge and how much you make use of your battery system. Your pay-back period will be longer than estimated as it is likely you will have less discharge than the useable capacity unless you optimize your energy generation to accommodate discharge usage.
  • A battery system reduces capacity over its lifespan
  • There may be efficiency losses between solar, the battery and your appliances.

FAQ #

What is needed for an off-grid solar system?

For an off-grid solar system, you would need 4 components; the standard solar panels and inverter (an off-grid variant), along with; charge controller and battery bank. A battery bank is used to store energy generated or taken from the grid; a charge controller is also installed to prevent batteries from overcharging. 

How big of a solar system do I need to go off-grid?

You don’t need a minimum number of solar panels to go off-grid, you can size it however you want but to make the most of an off-grid system, you would want to size a system that is slightly larger than what can accommodate your energy usage. This is to account for any inverter inefficiencies, voltage drop and other losses. Typically for an average family home of 4 or more people, a 5-kW system is usually recommended, this may change depending on how much savings you want to make with your solar system. 

Why do I need a generator for an off-grid solar system?

You do not require a generator for off-grid per say, though it is very helpful in certain situations. Generators use petrol as fuel and are a means to generate power whenever you want. Living off-grid means that you won’t take any electricity from the grid, as such a generator can help provide extra power whenever you need it. Generators are typically small in size and thus can be stored away easily, they are popular for caravanning usage where people expect to need a little more power when going on long trips.

What are the benefits of living off the grid?

The benefits of living off-grid is having energy independence, providing homes or businesses security where you will still have access to electricity despite power outages and have price stability, as energy prices may fluctuate depending on season; peak hours and demand-supply. You will be completely self-sustainable and may potentially save more money in the long-term provided you size your system enough to cover all your energy usage.

Is going off-grid worth it?

The only reasons to want to go off-grid are: you live in a rural area without connectivity to the grid, want to be completely independent from the grid or live in a mobile home such as a caravan or a boat. If your goal is to save money, going off-grid would not be for you; due to the high upfront cost of battery systems despite government subsidiary. It is much better to stay on-grid where you have access to a feed-in tariff and convenient grid-connectivity.

Which is better between on-grid or off-grid solar

Say you lived in the outback, grid connectivity is not easy and chances are electricity costs are sky-high. In such a case, going off-grid allows you the ability to generate your own electricity and not have to experience any electricity shortages from the grid if there were one. This also translates well to mobile-home owners, where you can generate electricity on the go without having to stop for fuel. Bear in mind the added-weight of panels and batteries, if you are in a mobile home as you would need to mount it on-top of your vehicle (this may not be necessary if your home is stationary often, where you can have a ground-mounted system), be wary of what weather can do to your components. Off-grid is worth it for those who may not have access to the grid, have higher-than-average electricity costs, or live-in areas with major power outages. With the current pricing of off-grid systems, it is more worth it to stay on-grid along with access to the grid and a feed-in tariff.