Most solar panel with battery backup systems have options for how to use your batteries. There is often confusion around this because some of the modes of operation sound great. However, in most cases, there is no benefit to Southwest Florida residents to use anything but “Full Backup” mode.
Battery and inverter system manufacturers call the various modes by different names, but they all have the same basic options. We will stick with the Enphase battery mode names since that is what most of our clients have. The options are Savings, Self-Consumption, and Full Backup. Here is what each means and why you might use them.
This mode is designed for something called Time of Use utility billing. In some areas of the country, residential utility customers are billed different electricity rates based on the time of day. And the peak and off-peak times may change based on the time of year. This is done because it costs all utility companies more money to generate energy when demand peaks, and they want to encourage homeowners to reduce their electricity use at peak times.
To defeat this, solar panel owners can use batteries to smooth our their electricity usage and draw less from the utility company during peak rates, or even sell stored solar energy from batteries back to the grid for maximum benefit. During off-peak times, there is little benefit to selling solar energy to the grid, so excess solar energy can be stored in batteries.
By default, residential and business customers are not billed based on time of use in Florida. Energy rates are the same throughout the day and night. Most Florida utilities will allow you to voluntarily subscribe to time-of-use billing. This works best if solar production occurs during peak energy rate times, which is not really the case in Florida. It would be exceedingly rare for someone to be able to benefit from making this switch, and very risky since peak rates are very high. Essentially, Savings Mode is of no benefit for Florida system owners.
As the name suggests, this mode maximizes your use of solar energy in your home. It minimizes the selling of electricity to the grid, or stops it altogether. At first, this mode sounds appealing to people, because they think that maximizing the use of solar somehow has a financial benefit. That is not the case in Florida, and it actually has the opposite effect.
We have full net metering here, which means the utility company gives you 1-for-1 credit for each unit of electricity you “sell” to the grid. If you send a kilowatt-hour of electricity to the grid, the utility company owes it back to you. Your meter simply spins backward and forward and you are billed for the net amount of energy used (if any). The grid acts as a “bank” for your excess energy, giving it back to you at night or in future billing periods when you have a shortfall of solar production.
Self-Consumption mode is designed for locales where there is no net metering, or if the utility provides a different rate for energy sold and purchased. If you are not allowed to sell excess power to the grid, excess solar power would be wasted, so storing it in a battery inside your home would be beneficial. If the utility is going to pay you significantly less for the excess energy you send to them, you might be better off storing it for yourself for future use. Since we have 1-for-1 net metering here, none of this applies to Southwest Florida residents.
If you are contemplating self-consumption just because is sounds good, despite lack of net metering benefit, be forewarned. There are efficiency losses associated with charging and discharging a battery. You will be wasting some solar energy in this conversion process. And more importantly, you will be reducing the cycle-life of your battery. Batteries lifespans are rated in the number of discharge cycles, and will deteriorate over time if heavily discharged and charged repeatedly.
There is one unique circumstance where self-consumption may be beneficial. If you have a property insurer that does not allow net metering, you can use a battery to store the excess energy generated during the day and discharge the battery at night to your home. The insurance mess in Florida is causing some uninformed insurers to reject net metering because of some perceived liability issue that does not exist. This is a subject for another [long] article.
If you have not figured it out yet, this is the mode you want. Full backup simply keeps batteries charged to full capacity so they are ready when a grid-outage event happens. Obviously, you want to start with a full battery when the grid goes down. The other modes could leave you with a deeply discharged battery at the time you need it most in a backup scenario.
Since there is no financial benefit here for time-of-use (Savings) or self-consumption, Full Backup is likely the only mode you need.
Enphase offers a feature called Storm Guard, which can switch your system to Full Backup mode when there is a National Weather Service alert for your zip code. This does nothing when you are already in Full Backup mode. If you use one of the other modes, you can enable Storm Guard to have your batteries ready when an outage is most likely. If you are on a no-export mode system, you will still export no power to the utility, but your excess energy will be lost when Storm Guard is in effect if your battery is at 100%. Most clients don’t need to worry about this.
If you do use self-consumption mode, we suggest that you set the maximum discharge to 70% (30% minimum capacity). This will improve the lifespan of your battery. If you are losing excess solar capacity, you can drip this to 20% minimum capacity or preferably add battery storage to absorb the excess.
We do not recommend adjusting the Battery Shutdown Level. Leave it at 10% unless you have a very small solar panel array relative to your battery capacity.
You can set your system to charge your battery from the grid. Be aware that the applicability of solar tax credits requires that 100% of battery recharging must be from solar power, so technically you would be putting your tax credit in jeopardy if you activate this setting. Nobody will ever know, but technically this is the way it works. You might want to turn this setting on after a storm where the utility power is coming and going if your battery is deeply discharged. If the utility power comes on for a brief time, you might be able to store up some power. This would be a rare scenario, but it’s nice to know this feature is available.
Selecting The Right Battery Mode
For the vast majority of users, we “set it and forget it.” There is no reason to change your settings, as they have been optimized for your scenario. The system is designed to be seamless and no interaction is required. It just works, providing backup power when the grid is lost and reconnecting to the grid when it returns.
If you have questions about your settings and how to maximize your investment, reach out to us and we will be happy to help.