Enphase Bi-directional EV Charger: V2G for any solar home
An upcoming EV charger by microinverter company Enphase will enable vehicle-to-grid technology. Here's what that means, and why it's significant.
Enphase recently announced that it is releasing a bidirectional electric vehicle charger. This means that not only is it capable of charging a car, but also drawing power from a car and sending it to your home or the grid.
This is unique because most EV chargers are unidirectional, which means they’re only capable of sending electricity in one direction - from the electric grid (ie. your home) to the car. By adding bidirectional capability, the Enphase EV charger will let solar homeowners have some of the same advantages as owning a home battery but without the high cost.
The bigger picture is that policy makers, utility companies, and tech companies have been working on vehicle-to-grid (V2G) for some time, but with only limited deployments so far. Enphase’s new EV charger has the potential to bring this technology to market more widely and with fewer policy hurdles.
We’ll take a closer look at Enphase’s new EV charger, and what it means for V2G and V2H (vehicle-to-home) charging in general.
What is vehicle-to-grid (V2G) and vehicle-to-home (V2H)?
Vehicle-to-grid and vehicle-to-home technology is the ability to send electricity stored in an electric vehicle into a home or the broader electric grid. It’s basically the reverse of EV charging.
In North America, we’ve standardized on the J1772 connector for charging electric vehicles using AC power. When you plug your car into one of these chargers, the battery will charge at a maximum of 80 amps or 19.2 kW.
V2H enables the reverse, allowing power to be drawn out of the vehicle’s J1772 port to power a home. V2G is similar to V2H, except that it’s intended to provide power to the general electric grid, and not just a single home. Hyundai also uses the more generic term vehicle-to-load (V2L). Whatever the term, the feature is the same: sucking power out of an EV to power something else.
When you think of it, a grid-connected solar home is performing a similar role whenever it’s sunny and your home isn’t using much power. In that situation, the excess solar electricity is sent into the grid where it is used by other customers in the neighborhood, helping to reduce the net load on the local grid.
V2G is currently supported by a few EVs on the market, including the Ford F-150 Lightning, Hyundai Ioniq 5, and Nissan Leaf. In most cases, this feature is marketed for smaller-scale applications. For example, Ford calls this feature Intelligent Backup Power and Hyundai says that it’s a way to power small appliances or charge another EV. Except in limited pilot projects, EVs aren’t yet being used to specifically support the grid.
What is the purpose of vehicle-to-grid?
V2G a technology that electric grid planners and companies have been working to make a reality because it has the potential to assist the electric grid as more and more electricity is being produced by intermittent sources like wind and solar power.
Renewable technologies like wind and solar have the huge benefit of being clean and inexpensive - cheaper than fossil fuels in most cases now. Their main disadvantage is intermittency. For the grid, the increasingly common solution to intermittency is the same one that’s being deployed in more and more solar homes - batteries. When the sun goes down or winds drop to a lull, grid-scale batteries can fill the gap for the grid. In the past few years, the market for grid-scale battery storage has exploded, with gigawatt-hours of storage now being added to the US every year.
The technology behind this is lithium-ion batteries - the same that’s in your smartphone, EV, or home storage battery. In fact, Tesla’s Megapack for utility-scale storage is the same basic technology that’s used in their popular Powerwall for homes.
In its fully-realized form, V2G technology could be enabled on-demand by electric grid operators when the need arises. For example, on hot summer days when the electric grid is strained by the heavy use of air conditioning, grid operators could send a request to V2G-connected EVs and have them supply power to the grid. Given that the duck curve is already a problem in states with lots of solar power, the ability to use hundreds of thousands of otherwise idle EVs to support the grid could be a huge benefit that is also cost-effective.
The Enphase Bi-directional EV Charger
Enphase recently acquired the EV charging company ClipperCreek, so it’s not surprising that Enphase is releasing new EV charging products.
At the time of writing, the bidirectional EV charger is an upcoming product, so there are no specifications (such as EV charging amperage) that are known yet. However, given their acquisition, it’s reasonable to assume that its charging capability will at least be on par with existing ClipperCreek products.
From Enphase’s description, it sounds like the V2G feature of the EV charger will provide the same kinds of functionality as an Enphase IQ Battery. Specifically, Enphase says that the software of its charger will provide the following features when in V2G mode:
- Green charging
- Savings mode
This makes a lot of sense, and you can understand what Enphase is thinking here: the Bi-directional EV Charger is functionally the same as an Enphase IQ Battery, except that your EV is providing the battery storage. The “smarts” of the IQ Battery - the software that enables different discharge modes and the smartphone app - have essentially been transplanted into an EV charger.
How can the Enphase EV Charger support the grid?
Smart batteries like the Tesla Powerwall and the Enphase IQ can be configured to discharge electricity into a home when the grid needs it most - during utility peak hours. This is when utility companies set prices at their highest, which encourages customers to save electricity when the grid under its highest load.
Peak rates also provide home battery owners an incentive to set their batteries to discharge during peak hours. That’s what the Savings Mode of the Enphase IQ Battery and the Bi-directional EV Charger do - they use the battery to power your home, allowing any excess solar electricity to be fed into the grid.
This accomplishes the same grid-supporting goal as V2G technology, though without the direct control over demand response that utility companies desire.
How the Enphase Bi-directional EV Charger will work
The clever aspect of the Enphase charger is that it will enable V2G for solar homes without any of the coordination that would otherwise be needed between utility and technology companies.
An electric vehicle can’t simply start sending juice into the grid without an interconnection permit from the utility company. However, a solar home requires interconnection and a special meter from the utility company, so that hard part is already done.
The upshot is that adding the Bi-directional EV Charger will, from the point of the utility company, will be the same as adding a conventional home battery. In fact, the utility company won’t be able to tell whether the electricity a home is sending into the grid came from a home battery or a car.
For the homeowner, the EV Charger will require the same system layout as a solar home with Enphase microinverters and an Enphase IQ Battery. The Enphase System Controller, which provides the overall brains of the system, will be required, just as it is with an IQ Battery.
As you can see in the diagram, the EV Charger is connected to the System Controller, just the same as an IQ Battery. In fact, it appears that a homeowner could have both the EV Charger and an IQ Battery as part of their system.
Solar-only charging is a great benefit for anyone with net billing, including California NEM 3.0
Solar homeowners with net billing receive a credit for solar electricity they sell to the utility that’s less than what they pay for grid electricity. This includes California’s new NEM 3.0 scheme, even though California (incorrectly) calls it net metering.
Net billing gives solar homeowners a strong price incentive to consume all of their own solar electricity rather than sell it to the utility for a discount. Electric vehicle charging is one of the “appliances” in a home that can consume enough electricity to make a difference: charging an EV can easily consume all of the output of a home solar array.
There’s where the “green charging” feature of the Enphase EV Charger comes in. Green charging will automatically use any excess solar electricity to charge a vehicle that’s plugged in, rather than sending it to the utility for a discounted credit. For solar homeowners with net billing who are trying to figure out how to get the biggest financial benefit from solar, this green charging feature can make a big difference.
The other advantage is that the electricity used to charge an EV in this scenario is coming directly from the microinverters. This means fewer electrical losses, especially compared to using electricity stored in a home battery to charge an EV.
Pros and cons of the Enphase Bidirectional EV Charger
Home storage batteries are an increasingly popular addition to solar homes, especially with the introduction of NEM 3.0 in California. If you have solar panels and an EV, the Bi-directional EV Charger could be a great solution for getting a lot of the same benefits of a battery with less expense.
While the product hasn’t been released yet, based on the product description we can expect the following pros and cons:
- EV charging capability
- Enables vehicle-to-grid transfer
- Less expense than a home battery
- Battery storage functionality requires the vehicle to be plugged in
- Power output limited by EV capability, and can be low
- Can increase EV battery degradation
- No 30% federal tax credit
Depending on the amount of electricity that the vehicle is capable of sending to grid, degradation of the EV battery may or may not be a concern. For example, an Ioniq 5 is capable of only 15A in V2L mode, which is quite small compared to how much electricity is used by the vehicle when operating. The F-150 Lightning, however, is capable of a significantly higher 40A output.
In any case, battery degradation might not be much of a concern: reports are that Tesla batteries experience only about 12% capacity loss after 200,000 miles of driving.
While there is no price information released yet, we can assume that the Bi-directional EV Charger will be much less expensive than a standalone battery. However, some of the price advantage is reduced because home batteries qualify for the 30% federal tax credit.
Wait and see, but it could be a great product for some
At the moment, Enphase hasn’t set a release date for this product, except that it will be available in 2024. That’s quite awhile yet, so if you are needing EV charging now, the Bi-directional Charger might not be for you.
However, if you’re planning to add EV charging to your home in the future, it could be an excellent solution to adding some limited backup power for blackouts. It can also be a great way for Californians under NEM 3 and other net billing customers to maximize their savings - but only if your vehicle is home and plugged in when the sun is shining.
I’ll be sure to update this article as further details are released.