Battery Backup for your Solar Installation

One of the most common questions we get at Skylit is: “What happens when the power goes out? Will my solar still work?” For simple grid-tied systems, the answer is no. However, we can add battery backup to an existing solar PV array, or with a new installation, to keep essential loads operating in the event of a power outage. This will also allow your solar panels to continue to produce power during the day when the grid is down.

Solar and Battey Backup

How does this work?

The battery system is designed to work with a Solar PV array. It is wired into a new or existing essential loads panel (a separate panel containing the circuits you want to keep operating during an outage. You may already have one if you have a generator).

First, let’s look at the system’s functionality during daytime hours. During the day the battery and hybrid inverter can trick the inverters into thinking the grid is still operational. This will allow your solar PV system to continue producing power. This power from the solar will first satisfy the demand in the essential loads panel and any excess production will charge the batteries.

If at any point the generated solar power exceeds both the loads demand and the need for battery charging (i.e., the battery has reached full capacity), the hybrid inverter will turn the solar off as there is no place for the extra generation to go.

When this happens, you can decide to use more power on certain loads that could be useful, instead of stopping generation. You could, for example, decide to run a water pump to fill a bathtub, make a hot meal, heat or cool your home, or charge devices.

There could also be times during the day, like if it’s raining, snowing, or very cloudy, when your solar array may not be able to deliver required power to your backed-up loads. In this scenario, the generated power will be supplemented with your installed battery to fulfill the requirements of the loads in your essential loads panel. When this happens, you may want to reduce your power requirements to ensure you do not drain your batteries before nightfall.

What about at night?

The next thing to look at is your battery systems operation during the evening/overnight when there is no solar generation. During this time, you will be reliant on the battery only and monitoring your usage (battery drain) can be much more important than during the day. This can be done through the hybrid inverter’s monitoring system.

The other thing to consider is if there is a standby generator wired to this battery system. The hybrid inverter has terminals to accept a generator connection, and for self-starting generators the inverter can be programmed to start/stop the generator with low/high battery state of charge settings. In this case, you may not be concerned with battery drain during the evening with no solar production, or during the day if solar production is low due to overcast or inclement weather. A manual start generator can also be connected to the inverter to top up the batteries as required. It just requires monitoring the system to ensure your batteries don’t get too low before using the generator.

What we offer

Our SKYSTOR battery backup systems all use a 12kW Hybrid Inverter. Our standard system comes with two 5.12kWh batteries, giving 10.24kWh of storage; and our robust package has four to give you 20.48kWh of storage. The batteries can be discharged 90%, and are rated for over 6000 cycles for a very long life.

Typical loads that would run off a battery system are: a fridge, a microwave, lights and plugs for convenience and entertainment (including internet), a small heat pump, a water pump, sump pump, and freezer. Depending on your usage, two batteries could give you up to a day’s worth of power. Four batteries will provide resiliency for higher loads, or during extended outages with little sun. Of course, differences in age and types of appliances will mean different power consumption, and every family will use power differently. As you get to know your system you can optimize it to work best for you.

Don’t go through another power outage in the dark! Plug into the sun with a SKYSTOR battery backup system for your solar installation. Contact us for more details and pricing!

Amanda Brulé

Amanda is VP Sales & Residential Projects at SKYLIT.