Can My Older 100-Amp Service Handle an EV Charger or Heat Pump?

If you live in an older Westminster or Brighton home, you’ve probably got a 100-amp electrical service. That was perfectly fine when it was installed—enough to run your lights, appliances, and maybe a window AC unit.

But now you’re thinking about adding an EV charger or switching to a heat pump, and you’re wondering: will my electrical panel keep up?

The short answer is: sometimes. It depends on what else you’re running and how you plan to charge or heat.

Our licensed Brighton electricians and Westminster electricians are here to guide you through what actually matters when you’re trying to figure out if your current setup can handle these upgrades—or if it’s time for a panel upgrade.

What’s Actually Drawing Power in Your Home?

Before we talk about adding anything new, let’s look at what’s already using electricity. A typical 100-amp service can handle about 24,000 watts at any given moment (100 amps × 240 volts). That sounds like a lot until you start adding things up:

• Central AC: 3,000–5,000 watts
• Electric range: 3,000–5,000 watts
• Electric dryer: 3,000–4,000 watts
• Water heater: 3,000–4,500 watts
• Refrigerator, lights, electronics: 2,000–3,000 watts combined

You’re not running all of these at once most of the time, which is how 100-amp service has worked for decades. But when you add a heat pump (which can pull 3,000–7,000 watts depending on size) or an EV charger (anywhere from 1,400 to 11,500 watts), you’re pushing closer to that 24,000-watt ceiling. And that’s when things get tight.

EV Charging: Not All Chargers Pull the Same Power

A Level 1 charger plugs into a standard 120-volt outlet and draws about 1,400 watts—roughly the same as a space heater. Your 100-amp panel can handle that without breaking a sweat, though you’ll only add about 4–5 miles of range per hour. Fine for overnight charging if you don’t drive much.

A Level 2 charger runs on 240 volts and can pull anywhere from 3,800 to 11,500 watts depending on how it’s configured. That’s the one that gets you 25–40 miles of range per hour, which is what most people want. It’s also the one that can overload a 100-amp panel if you’re not careful about what else is running.

Heat Pumps Add Another Layer

Heat pumps are efficient, but they’re not low-draw. A typical residential heat pump for heating and cooling pulls between 3,000 and 7,000 watts when it’s working hard—which in Colorado means cold winter mornings and hot summer afternoons. If you’re already running other major appliances and you add a heat pump to a 100-amp service, you might be fine most of the time. But on the coldest day of the year when your heat pump is running full blast and you plug in your EV, you could trip breakers or overload circuits.

Load Calculations Tell You What’s Really Possible

This is where guessing stops and math starts. A licensed electrician can run a load calculation on your home—basically adding up everything that draws power, how often it runs, and what your peak demand looks like. That calculation shows whether your 100-amp service has headroom or if you’re already close to capacity.

If the numbers show you’ve got room, you might be able to add an EV charger or heat pump without upgrading. 

If you’re already pushing limits, you’ll need to make changes. Our team does these assessments regularly for homes throughout the Westminster and Brighton area, and we can tell you exactly where you stand.

Smart Solutions That Don’t Require a Full Upgrade

Sometimes you can add what you need without replacing your whole panel. Here are a few ways to make it work:

• Load-sharing devices: These are smart systems that monitor your home’s electrical draw in real time and automatically reduce charging speed when your dryer or AC kicks on. When demand drops, charging speeds back up. You get your EV charged overnight without overloading your panel.
• Lower-amperage EV chargers: Instead of installing a 48-amp charger (11,500 watts), you can install a 32-amp or even 24-amp charger that draws less power. You’ll still charge faster than Level 1, just not at maximum speed.
• Subpanels with smart controls: If your main panel is full but you’ve got capacity on your service, adding a subpanel with load management can give you room for new circuits without a full upgrade.
• Timing your usage: If you’re home during the day and can avoid running major appliances while your EV charges overnight, you might be able to get by. Not ideal, but sometimes practical.

These strategies work well for some homes. For others, they’re just a Band-Aid, and a real electrical panel upgrade makes more sense.

When a Service Upgrade Actually Makes Sense

If your home needs more power than these workarounds can provide, upgrading to 200-amp service is the right call. It costs more upfront, but it gives you room to grow—not just for an EV charger or heat pump, but for anything else you might add down the line.

An upgrade also means your electrical system meets current code, which matters for safety and resale value. Older panels with federal pacific or Zinsco breakers are known fire hazards and should be replaced regardless of capacity issues. If your panel is one of those, an upgrade isn’t optional.

We handle electrical panel upgrades in Westminster, Brighton, and surrounding communities, and we’ll walk you through what’s involved, what it costs, and whether rebates or incentives apply to your situation.

Available Rebates and Incentives

Colorado and some utility companies offer rebates for EV charger installations, panel upgrades tied to electrification, and heat pump installations. The Colorado Home Energy Rebate Program provides income-qualified households with rebates on electrical panel upgrades when installed alongside heat pumps and other electric appliances. Federal tax credits are also available for electrical panel upgrades through the end of 2025 when installed with qualifying equipment. Xcel Energy and other utilities may offer additional incentives through their own programs.

We won’t quote specific amounts here because they change and depend on your income level and the specifics of your project, but it’s worth asking about when you’re planning your upgrade. Sometimes the rebates and tax credits cover a meaningful chunk of the cost.

Call Us For Your Load Calculation

If you’re thinking about adding an EV charger or a heat pump to your Brighton or Westminster home, don’t just guess whether your 100-amp service can handle it. Get a load calculation done. It takes about an hour, and you’ll know exactly what’s possible with your current setup—and what’s not.

From there, we can recommend the best path forward, whether that’s a load-sharing device, a panel upgrade, or something in between. Every home is different, and there’s no one-size-fits-all answer.

Ready to figure out what your home can handle? 

Contact us to schedule an on-site load assessment. We’ll give you a clear upgrade plan that works for your home and your budget!

Call Now (720) 774-0192