Battery savings seasonality issues

Battery utilisation can be optimised by buying grid energy, storing it and using it later in the day. But its not so lucrative, it depends a lot on having favourable energy plan pricing.

One more graph about home batteries this week... but first, a quick ask. Let's get into this week's topic, the third and last part of the battery analysis.

A 13.5 kWh battery is over charged in the summer and under charged in the winter, a utilisation issue

In the last two articles, I discussed how batteries still aren't at the break-even point financially or really even in the same neighbourhood.

But for most, that isn't the main motivator to buy a battery, rather than thinking about buying a battery to make money, it's more about purchasing a certain degree of energy independence from the grid. If the battery breaks even towards the end of its life, then that's a bonus.

Though before we wrap up this battery analysis, I want to take one more look at the seasonality of batteries.

We're looking again at the same coastal NSW home we've looked at before. The home has a 6.6kW solar system facing north and is considering installing a 13.5kWh battery. In our analysis of how much savings they could get out of the battery, we saw some clear red flags for their specific use case.

To cut to the chase, in summer, the battery is charged to the brim and can rarely discharge 20% of its available power before entering the next charge cycle. This means there is power waiting to be used, which is lost savings.

As a stark contrast, in winter, the battery struggles to get a charge over 2.5kWhs in the afternoon, which quickly gets eaten up by the energy demands of the home as soon as the sun goes down. Again lost savings, but now because the battery could have held power for the home to be used later in the day when their peak energy prices kicked in.

On the left and right sides of the above chart, we can see the low levels of charge the battery would reach. For most of the winter months its barely keeping above 2 kWhs. In the summer months, the battery consistently reaches peak charge and, for December, stays at peak charge quite often.

The end result is this battery is not being utilised to its full potential in either winter or summer because there's either not enough solar energy or too much.

Joining a virtual power plant program so your battery is being utilised more often

Virtual power plant programs or VPPs are a black box for the uninitiated like me, so I can't confidently say how optimal they are in utilising a battery's potential.

But, at least we can figure out half the story! Two articles ago, or a month ago, I simulated what this same battery would look like if it were charged with grid energy in the winter months and that energy was used through out the day.

Now, in the winter months, we can see how a more efficient battery is utilised. For this specific home, the battery is charged in the morning before its peak price kicks in, and then throughout the day, it can discharge that energy as needed.

This is how a VPP would function as well. Charge the battery when energy is cheap and discharge it later. However, in a VPP, people will most likely pay different prices for that energy, so it's not a perfect one-to-one match when discussing savings. If you got a chance to read that article last month you'll remember that purchasing the grid energy to use later in the day saved this home 10 to 15% more on their yearly energy bill. But the home was also on a harsh peak and off-peak time schedule that made it difficult to optimise the battery so this had its caveats as well.

One other thing to note in the above graph is we aren't optimising the summer months. Either the home or a VPP program will need to use the power in some way to really discharge the battery and get the most value possible.

Maybe a VPP in summer and a more attractive grid charging cycle in winter will boost the battery savings enough to make a sizeable dent. If you have a battery at your home I'd be keen to hear your story and how you've found these seasonal peaks and troughs.

If you have Enphase inverters on your home then reach out

To access all this data for this analysis the homeowner easily connected their smart energy meter to their own SolvingZero dashboard in just a few clicks—and for free! No devices or house visits were needed.

The next step we working on is connecting to solar inverters. Once connected we can use the generation and consumption data stored inside the inverters. If you'd like to be part of our free pilot program to create full energy profile of your home then reply to this email.

If you are not with Enphase or don't even have solar then no worries either! We are able to connect your own personal dashboard to your smart meter and show you how much money a solar system would save you based on your consumption patterns.

In the future we plan to also connect with other inverter brands too, so stay tuned as we roll out this program. Create your own energy dashboard for your home to get started.