Many EV owners encounter multiple inefficiencies today. Evening charging coincides with peak prices. Standalone vehicle-to-load (V2L) or vehicle-to-home (V2H) are available for power backup, but using the vehicle as the primary backup source adds extra charge/discharge cycles and heat stress to the traction battery, accelerating battery degradation.
This is where a home energy management system (HEMS) redefines the way you use your EV. It can automatically shift charging to lower-cost windows, prioritize the stationary home battery for routine backup, and dispatch EV power only when appropriate to protect short term needs.
The article explores how integrating EV power into a HEMS can lead to improved home energy efficiency, resiliency, and controlled EV battery impact.
Dedicated Home Battery in a HEMS vs. EV Battey: The Key Differences
Dedicated Home Battery
Designed specifically for residential energy use, a home battery can withstand the frequent, deep, and rigorous daily duty cycling demands, with intelligently managed operation.
- Long lifespan: A home battery typically supports over 6,000 cycles, rendering a durability that can handle frequent and continuous charge/discharge cycling without significantly compromising its capacity when used as intended.
- Addressing time-of-use (TOU) tariffs: The HEMS dynamically adjusts to fluctuating electricity rates, charging the battery during off-peak hours, and releasing during expensive periods to avoid peak grid charges.
EV Battery
While the advent of EVs ushers in a new era of sustainable mobility and cleaner air, uncoordinated home charging and unplanned use of V2L/V2H can increase energy costs, reduce efficiency, and place unnecessary wear on the EV battery.
- Shorter lifespan compared to home batteries: EV batteries are optimized for driving, typically enduring around 3,000 charge cycles. This lifespan aligns with automotive expectations but is not ideal for the frequent, constant cycling of daily energy use.
- Evening charging elevates peaks and costs: Plug-in behavior often clusters after work, which happens to align with peak grid demand and peak tariffs. This significantly increases electricity bills and grid stress.
- Extended parking leads to standby losses: Onboard systems can draw power when your EV is sitting (vampire drain), gradually lowering the state of charge over days or weeks.
- Regular, standalone V2L/V2H use will impose faster EV battery wear: When your car becomes the main power source for the house during outages, it racks up extra charge/discharge cycles and heat. How much it degrades depends on the depth of discharge, temperature, and frequency of use.
How HEMS Load-Shifting Shaves Home Charging Costs
When integrating an EV into a HEMS, the system can decide when to charge your EV so that most of the grid energy draws land in the cheapest, lowest-impact hours, without you attending to the schedule.
TOU rates alone help a little by nudging you off-peak, but managed charging makes a huge difference. With a HEMS, the system actively shifts the bulk of your charging into low-price windows and away from the evening rush.
Multiple field programs show the same pattern: managed charging reliably shifts a significant share of EV charging from busy, expensive hours to quieter, cheaper times, reducing local demand spikes on neighborhood lines and transformers. For example, in California, there are trials using smart charging that automatically adjusts to changing prices. Consequently, up to 98% of charging occurred off-peak, far outperforming TOU alone (ev.energy). Industry analyses further estimate roughly $300 per EV per year in additional customer savings for active managed charging versus TOU-only approaches. (utilitydive).
The FranklinWH System is an epitome in intelligent management of EV charging. The Smart Circuits in the system allow you to place the EV charger on a dedicated, controllable circuit and schedule it for late-night off-peak hours, say 2:00 a.m., so most charging happens when rates are lowest. Through the FranklinWH App, you can schedule start/stop times, align with your utility’s TOU windows, and automatically pause or shed the circuit during outages to preserve home battery reserve.
How Solar Can Be Leveraged to Charge EVs at Midday through HEMS
As HEMS technology advances, more companies are enabling solar-to-EV charging during midday when your panels are producing the most. A HEMS can intelligently coordinate household loads, the home battery, and the EV in real time so that power surplus to home loads flows straight into the EV. If you are not home during the day, you can still set the HEMS to charge your EV by drawing stored solar in the home battery in the night.
Leveraging self-generated energy to charge your EV not only raises the share of renewable energy powering your miles and cuts fossil-fuel consumption, but it also gives you a second way to save money by using stored solar so you’re not charging from the grid.
How V2L/V2H Integration with HEMS Strengthens Backup Resiliency
Integrating V2L/V2H into a HEMS turns the vehicle into a controllable energy asset, adding another layer of backup without over-cycling the EV battery.
V2L/V2H for Supplementary Power Backup
Your EV can serve as an additional energy source, supplementing the home battery during outages when it’s drained or home loads briefly exceed its output power. With an advanced system controller, the HEMS seamlessly dispatches the EV power to support the home battery, keeping your home powered.
HEMS Optimization
Within a HEMS, V2L/V2H utilization is intelligently optimized:
- Schedules charging into low-price windows
- Prioritize stationary home battery storage for routine backup
- Dispatch EV power during rare, high-impact moments without manual intervention
The result is stronger power outage protection via layered storage with intelligent management.
The FranklinWH System, for example, provides advanced EV integration technology, tapping into your EV power with a dedicated module in the aGate intelligent controller that connects to your EV. Homeowners can power their home by plugging into a native 240 V outlet on their EV (eg., Ford F-150 Lightning), distributing power through the aGate for intelligently managed power backup. This enables enhanced home energy resiliency.
Why Integrating Your EV into a HEMS Protects EV Battery Longevity
Integrating your EV with a HEMS protects your battery's longevity as opposed to a standalone V2L/V2H setup because the HEMS adds a crucial layer of intelligence and control, transforming your EV from a simple, constant power source into a strategically managed energy asset. A HEMS optimizes usage by strategically dispatching the EV's power only during outages as a last resort, prioritizing other sources such as solar or a stationary home battery first, which dramatically reduces the number of charge-discharge cycles on your EV.
It also manages high-power demands by leveraging a home battery to handle sudden spikes, sparing your EV from the most strenuous loads, thereby ensuring that powering your home doesn't come at the expense of your vehicle's primary function and long-term health.
Summary
The benefits of a HEMS to an EV homeowner are clear. Charging an EV without intelligent control can exacerbate peak electricity demand, straining the power grid and leading to energy waste, while a HEMS solves this by automatically shifting charging to off-peak hours, reducing electricity costs and carbon emissions.
Furthermore, when integrated with V2L/V2H technology, the HEMS improves home energy reliability: it ensures enhanced home power backup by leveraging the EV as a strategic energy reserve, mitigating fast EV battery degradation caused by unmanaged charging and discharging. That way, its health and longevity can be preserved while being an energy source.
