100 Amp Home EV Charging Solution - PowerSmart

There’s a lot of confusion out there about owning an EV if your house only has a 100-amp electrical panel. Search around online and you’ll see plenty of people saying you must upgrade to 200 amps before you can think about charging at home. I’m here to tell you that’s not true.

Yes, a bigger panel gives you more breathing room, but you can absolutely run a Level 2 charger on 100 amps if you’re smart about it. The main concern is that the panel has less headroom for things like the oven, dryer, or AC running at the same time. If too much happens at once, you can push the system to its limit.

When I first got my Bolt, I was careful to only charge overnight when nothing else was running. That worked for me, but not everyone in the house remembers to think that way. I needed a solution that could keep everything safe without requiring constant attention.

That’s where Emporia comes in. They make the smart charger I use, and they also sell the Vue Energy Monitor. The Vue is a little device with sensors that clamp onto the main service wires inside your panel. It watches how much power your house is using in real time and talks directly to the charger.

Here’s the clever part: if the monitor sees the house pulling close to the 100-amp limit, it tells the charger to back off automatically. As soon as things calm down, charging speeds back up. No breaker trips, no manual scheduling, no stress.

The monitor itself costs about $99 for the base version, and if you want to unlock the load management feature, called PowerSmart, in the app you’ll need to buy a software upgrade that runs $125–$200 depending on your charger. Compared to the thousands of dollars a panel upgrade can cost, it’s an absolute bargain.

If you’re comfortable with light electrical work, installing the Vue is pretty straightforward. The sensors just snap around the main service wires in your panel — nothing gets cut or spliced. Hook it up, connect it to Wi-Fi, pair it with the charger in the app, and you’re off and running.

DIY Setup Guide

If you’re comfortable working around your panel, this project is very doable as a DIY job. Here’s the basic process:

1. Install the Emporia Charger on a 240V circuit. If you already have a dryer or range outlet, sometimes a splitter can be used, but ideally you’ll want the charger on its own breaker.

2. Install the Vue Monitor by clamping the two sensors around the main service feeds in your panel. This step does mean opening the panel, so be cautious and take your time. The clamps snap around the wires — you don’t cut or strip anything.

3. Connect the Vue to Wi-Fi and link it to your Emporia app.

4. Enable the Power Smart feature in the app. This is a paid upgrade ($125–$200 depending on charger version).

5. Pair the Charger and Monitor. Once connected, the system automatically balances charging with your household power use.

6. Test it out — run a few appliances while charging and watch the charger throttle itself down when needed.

I’ve had this setup running for a few weeks now and it has been flawless. Charging happens at the maximum speed my house can handle, and I can see exactly where my power is going in the app. Owning an EV with a 100-amp panel is totally possible, and Emporia’s system makes it easy.

Understanding the National Grid Off-Peak EV Program

When I first started reading about National Grid’s Off-Peak EV Charging Program, I noticed a lot of confusion online (especially on Reddit). The good news is the program isn’t complicated once you break it down. If you drive an EV in Massachusetts and charge at home, this program can save you money just by plugging in at the right time.

How It Works

National Grid wants to encourage EV owners to charge their cars when the overall demand for electricity is lower. If you sign up, you’ll earn a rebate every month for charging your EV during off-peak hours.

• Off-Peak Hours: Weeknights from 9 pm to 1 pm the next day

• Peak Hours: Weekdays from 1 pm to 9 pm

• Weekends and Holidays: Treated as peak hours all day (no off-peak rebates)

Holidays That Count as Peak

Here’s the full list of holidays when charging is considered peak all day, even overnight (meaning no rebate):

• New Year’s Day (observed)

• Martin Luther King Jr. Day

• Presidents’ Day

• Memorial Day

• Juneteenth

• Independence Day

• Labor Day

• Veterans Day (observed)

• Thanksgiving Day

• Day After Thanksgiving

• Christmas Day

So, for example, if you plug in your EV at 10 pm on the 4th of July, it won’t count as off-peak and you will not receive a rebate.

Why It Matters

This program gives you cash back as bill credits every month just for smart charging. The exact rebate can vary, but the idea is simple: the more you shift your charging into off-peak hours, the bigger the benefit. And you don’t have to change how you drive, just when you plug in.

Bottom Line

• Charge on weeknights after 9 pm and before 1 pm the next day.

• Avoid charging during weekday afternoons, weekends, and the listed holidays if you want to maximize your rebate.

It really is that simple once you see the breakdown.

How to connect your charger to the program

National Grid doesn’t just take your word for when you’re charging — your charger needs to share charging data with them. Here’s how that works:

1. Get a compatible smart charger.
   Not all chargers can talk to National Grid. Popular options like ChargePoint Home Flex, JuiceBox, and Emporia are supported.

2. Download the app for your charger.
   Each smart charger has its own app where you can create an account. Once your charger is installed, you’ll get instructions (or see a menu option in the app) to connect with the National Grid program. 

3. Link your account to National Grid.
   Usually this means logging into your charger’s account and approving data sharing. You'll also need to download the National Grid app to get this going. Here is the app for Android and iOS.

4. That’s it.
   From there, National Grid can see when you’re charging. You just need to plug in during off-peak hours to earn the credit.

If you need more information you can visit the National Grid page for this rebate program.

Picking and Installing A Home Charger on 100-Amp Service

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When I bought my Bolt I knew I wanted the convenience of charging at home. The twist: my house has 100-amp service, and there’s a persistent internet myth that you must upgrade to 200-amp service to add a Level-2 charger. That isn’t true for the Bolt — with the right approach, 100-amp service is more than enough.

Disclaimer: I’m not an electrician — just an EV owner sharing my personal experience. Electrical work can be dangerous if done incorrectly. Always consult a qualified, licensed electrician before starting any electrical project. You are responsible for ensuring your work meets local building codes and safety requirements. I am not liable for any damages, injuries, or issues that may arise from attempting to replicate anything described here. 

After reading reviews and comparing features I went with the Emporia Classic. It hit the balance I wanted: not the cheapest, not the fanciest, but solid. The biggest benefit is that it's compatible with National Grid's off-peak program and can automatically schedule charging based on off peak hours. It charges reliably, has Wi-Fi and an app for scheduling and monitoring, and it offers both a plug (NEMA 14-50) option and a hardwire whip. Since my install was outdoors and I wanted a clean look, I chose the hardwire route.

Installation was straightforward because I had a lucky break: an abandoned hose spigot right above my electrical panel. I removed the spigot, mounted a single-gang outdoor electrical box, ran flexible conduit through the old hole, and pulled the properly sized wire to the panel. The Emporia hardware uses a ¾" threaded PVC conduit fitting which made connecting to the outdoor box easy and neat.

Why you don’t need 200A just to run a Bolt

A lot of people assume you need a 200-amp service for Level-2 charging — but the Chevy Bolt’s onboard AC charger limits it to roughly 32 amps (about 7.2–7.7 kW) on Level-2, so you don’t need a huge circuit to get useful charge overnight.

That was handy for me: I installed a 40-amp breaker for the charger circuit (a common choice), but I configured the Emporia to behave as if it were on a 30-amp circuit. In practice that gives me a safe buffer so the EV and the charger never try to pull the full 40A, while still topping the car overnight easily.

National Grid off-peak (what I enrolled in)

If you’re in Massachusetts and served by National Grid, they run an off-peak EV program that pays rebates for charging during designated off-peak hours. The program currently offers $0.05/kWh for off-peak charging in summer months (June 1–Sept 30) and $0.03/kWh in non-summer months (Oct 1–May 31). There’s also a one-time enrollment incentive in some rollouts. Charging must occur within Massachusetts and you generally enroll through the program portal or partner app. (Check National Grid for eligibility and the exact program window/dates — they publish full details).

A couple practical notes: confirm the exact off-peak hours for your account (they’re published by National Grid and can vary by program/version), enroll so your off-peak charging shows up in the program’s tracking tools, and set your charger schedule to charge during those windows for the rebate.

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Charging math (so you can see the real overnight numbers)

Assumptions I used (conservative & realistic):

• 2020-era Bolt usable battery capacity: ~60 kWh is a common conservative usable figure for many 2020 Bolts (some later replacements/upgrades push to ~66 kWh).

• Starting state of charge (SoC) for this example: 50%, so you need to add ~30 kWh to get to 100%.

• Charger/vehicle losses: account for ~10% charging overhead (heat/inefficiencies). I show results both without and with that 10% loss so you can see both ideal and realistic cases.

Power from a 240V circuit = 240 V × amps ÷ 1000 = kW.
So:

• 20 A → 240 × 20 / 1000 = 4.8 kW

• 30 A → 240 × 30 / 1000 = 7.2 kW

• 32 A → 240 × 32 / 1000 = 7.68 kW (Bolt is limited to ~7.2–7.7 kW by its onboard charger). 

HOURS to add 30 kWh (ideal, no losses)

• 20 A (4.8 kW): 30 ÷ 4.8 = 6.25 hours

• 30 A (7.2 kW): 30 ÷ 7.2 = 4.17 hours

• 32 A (7.68 kW): 30 ÷ 7.68 = 3.91 hours

HOURS to add 30 kWh with ~10% charging losses (realistic)

If we assume ~10% loss, you actually need about 33.3 kWh input (30 ÷ 0.9):

• 20 A (4.8 kW): 33.33 ÷ 4.8 ≈ 6.94 hours

• 30 A (7.2 kW): 33.33 ÷ 7.2 ≈ 4.63 hours

• 32 A (7.68 kW): 33.33 ÷ 7.68 ≈ 4.34 hours

Bottom line: even at the conservative 20-amp rate you’ll get a full 50%->100% overnight in under 7 hours (with losses). At 30A and 32A you’re easily done in a single overnight window (4–5 hours). That’s why the Bolt on a properly configured 30–32A L2 circuit is more than enough for daily commuting.

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Practical tips from my install

• If your charger supports setting a max breaker/amps (like the Emporia), set the charger lower than the breaker to keep a safety buffer. I used a 40A breaker and set the charger to run as if it were on 30A.

• Schedule charging during off-peak hours (National Grid) to capture rebates and lower per-kWh cost — the program’s tracking and rebate make this worthwhile.

• If you’re unsure about fitting conduit/wiring or local code, hire a licensed electrician. That money is well spent for a clean, safe install.

• Double-check connector and box sizes (Emporia uses a ¾" threaded PVC conduit fitting for the outdoor box on the unit I used) so your outdoor run is watertight and neat.