Getting residential storage right, why bigger isn’t always better

February 22, 2017 12:14 pm Published by Leave your thoughts

Sponsored article by Enphase Energy

Preserving the value of a solar investment

Households can expect an increase of up to 4.4 percent in 2017. Homeowners with rooftop solar will not be spared from these price hikes. In addition to these hikes, feed-in-tariffs, which have been ‘subsiding’ and helping to reduce overall energy bills for homes with rooftop solar systems in New South Wales, Victoria and South Australia, are now on the decline.

In 2017, the largest price increases are set to affect New South Wales, whose feed-in-tariffs will be shaved most drastically. The tariff reductions will see homeowners getting six to 10 cents/kWh for energy exported to the grid – this is potentially one third of the retail price of electricity purchased from the grid.

Having originally invested in solar systems to free themselves from the burden of power bills, many homeowners are looking to preserve their investment and stay free by investing in solar battery storage. As a result, the renewables market is currently flooding with energy storage products to meet the increasing demand and hype for this technology. The value proposition of these storage offerings tends to run along the same lines, storing excess solar generation for use during evening and morning peaks and for backup.

Capacity vs Cycling

Homeowners wanting to make the most of their battery system financially want to cycle their battery from zero charge to full charge and then back to zero daily. This cycle should capture as much of the homeowner’s excess as possible and ideally, cover as much evening and morning load as possible as well.










Fig 1. Enphase Storage System with MyEnlighten monitoring. The blue represents generation, the orange represents consumption and the green represents the battery’s charge. Notice how the battery cycles fully in the day and covers the majority of consumption at 12AM.


Unfortunately, a lack of education and a surplus of hype has led to homeowners considering and buying batteries with capacities that they do not need. Homeowners with existing 2-3kW systems buy into 6.4kWh systems which do not reach a full charge from their solar system and thus sit with unused capacity which is not utilised.

These systems often come with high power outputs and are touted as ‘backup ready’, this feature is genuinely useful for some homeowners who have solar systems which are able to fully charge these batteries but for most – by the time a blackout hits, the battery’s charge will be so depleted from general usage that it will not provide a very long source of continuous power in the case of a blackout. A storage system with a high power output is also more likely to reduce it’s nominal capacity much faster as well – resulting in warranties that only guarantee 50-60% nominal capacity remaining by 10 years.

So what do homeowners need?

A $10,000 price tag for larger battery storage systems is a steep financial investment for homeowners with pre-existing solar. While this price tag for larger storage systems is often justified by features like ‘backup ready’, the high power output that allows for this feature means that the battery’s usable life span is drastically reduced by daily usage. For most homeowners in Australia, who can expect one or two blackouts a year and for less than thirty minutes each, this is a gross overpayment for a feature that actually reduces the long term value of their investment.












Modular storage systems, such as the stackable 1.2kWh Enphase AC Battery, allow a knowledgeable installer to right size a battery system for homeowners’ current and future needs. Presently, the installer might just install enough to be financially palatable to the homeowner and later – once the funds become available – use the data from the first installation’s performance to retrofit additional batteries as needed. This philosophy ensures that homeowners are never paying for capacity and features which they are not using.

With batteries, bigger is definitely not always better.

Enphase Energy
03 8669 1679 // general enquiries AU
1800 006 374 // technical support AU