Battery Sizing, Equipment, and Pricing with Project Solar
First off, we want to state that batteries are not for everyone. Adding a battery does not make you "off grid" and will almost certainly lower the ROI of your project. It's not everyday that a company will tell you you probably shouldn't buy their offering, but we have a policy of treating every customer as we would treat our own mother.
Read more about batteries for off grid here.
That being said, assuming you still want a battery, we get it. Batteries are cool and they enable you to power your home in the event of the grid being down. They also can help smooth out the disparity between "time of solar production" and "time of use", although as of right now, most state and utility net metering policies make this less of an important factor in opting for batteries.
Read more about net metering here.
Batteries with Project Solar
Our preferred battery of choice is the Enphase IQ Battery 10 (previously known as the Enphase Encharge 10). This battery provides 10kWh of storage. Most homes use between 20-40kWh a day of power, so 1 battery is equivalent to 1/2-1/4th a typical home's daily usage. In a grid down scenario, you can turn off non essential loads such as AC, dishwashers, hot tub, etc, to prolong essential loads like lights and refrigerator/freezers.
The Enphase IQ Battery is built with internal micro inverters, continuing the same distributed strategy of the rooftop solar micro inverters, eliminating down time from a single point of failure. Additional, the Enphase IQ Battery is built using Lithium Iron Phosphate which is considered the safest type of lithium battery (less heat), with improved longevity and depth of discharge performance.
|Power rating||Energy Capacity||Peak Output||Rated Output||Round Trip Efficiency|
|3.84 kW||10.08 kWh||5.76 kVA||3.84 kVA||96%|
L:319.02 mm, W: 1070.1 mm, H: 663.96, Weight: 346 lbs
Additional Required Equipment
When adding a battery to your solar PV system, you need additional equipment to manage the system properly. The following items are included in our listed battery + installation pricing, with the exception of the sub panel ($750 adder if needed).
IQ Combiner: This box comes standard with all our "solar only" and "solar + battery" projects. It houses the breakers for the system and combines all strings into one. This is also the device that houses the wifi or cellular device to wireless communicate your system data to the cloud and your monitoring app.
Load controller(s): Not shown in the picture above, however, load controllers are important devices that work to automatically shed loads when off-grid.
System Controller: This is the traffic router of your system. The system controller works to deliver and draw power from the proper device. This is only needed systems that have multiple power sources such as with a battery or a backup generator.
Sub Panels/Critical Load Panels: A critical load sub panel is as it sounds. A secondary panel that houses the breakers for the loads you deem "critical" in the event of a power outage. In an outage, your battery is limited by its capacity and peak draw, so you most likely will not be able to power equipment with high peak demands or power hungry equipment that will quickly drain your reserves. Most customers opt to have the basics backed up, such as lights and refrigerators.
Battery Pricing and Sizing
The Enphase IQ Battery system can combine as many as 3 IQ Battery 10s together, providing 30.24 kWh of storage.
The general rule of thumb is 1 IQ Battery 10 per 10kW of solar. This of course, is subject to change based on your needs/goals.
Typically, if you have 10kW of solar and that is offsetting your daily usage, then 10kWh of storage would carry you through the night. It might, however, not be enough to power certain heavy equipment or to provide you with sufficiently long enough backup during an outage. But this is subjective and based on your risk tolerance/financial justifications.
1 IQ Battery 10 + System Controller + Install = $13,995 ($9,797 after federal incentives)
2 IQ Battery 10s + System Controller + Install = $22,695 ($15,887 after federal incentives)
3 IQ Battery 10s + System Controller + Install = $31,395 ($21,977 after federal incentives)
The first battery is the most expensive (on a per battery basis) because it requires so much installation time, materials, and expertise. Adding additional batteries adds minimal extra work, so you are mostly just paying for the additional cost of the equipment.
Solar with an IQ Combiner to grid tie installation is fairly straight forward, and relatively "easy". Installation of a system controller, sub panel for critical loads, and a battery is complex and technical, requiring years of training and licensing. We do NOT support DIY for system controller and or DIY battery installation.
Installation of these components takes about 6-8 extra hours from a licensed electrician. There are often additional components, wiring, breakers, etc that add considerable cost, but are included in our listed "battery + installation" prices.
All residential installs with Project Solar utilize Enphase Micro Inverters and the Enphase monitoring app. With the addition of the Enphase IQ Battery system, your app takes on another level of detail, showing the flow of electricity from your PV system to your battery to the grid to your home. The system controller automatically balances your system to maximize the return on your investment, optimizing battery usage for the hours of the day when the sun is not shining.