LoadWise

Home Electrical Panel Load Planner

Before you assume you need a costly service upgrade, see whether your panel can actually take the new loads.

Panel service rating (A)

Existing house load (A)

EV charger load (A)

Heat pump load (A)

Other new loads — induction, etc. (A)

Demand factor (%)

Spare capacity

36 A

A positive spare capacity means the loads fit under the panel's 80% continuous limit. This is a planning estimate — a licensed electrician must run a full NEC load calculation before any panel or service change.

Demand load: 124 A
Continuous limit (80%): 160 A
Panel utilization: 77.5%

What you entered

Panel service rating (A): 200Existing house load (A): 60EV charger load (A): 40Heat pump load (A): 30Other new loads — induction, etc. (A): 25Demand factor (%): 80

1
Total connected load
60 + 40 + 30 + 25 A= 155 A
2
Apply 80% demand factor
155 A × 80%= 124 A demand
3
Panel continuous limit (80% of service)
200 A × 0.8= 160 A
4
Spare capacity
160 A − 124 A= 36 A
5
Panel utilization
124 A ÷ 160 A × 100= 77.5%

Result

Spare capacity: 36 A

Your loads draw about 124 A against a 160 A continuous limit — 36 A to spare (77.5% used). These loads likely fit without a service upgrade; managed EV charging can add more headroom.

Panel headroom when adding an EV charger and heat pump

A panel's continuous limit is 80% of its service rating. Rows add loads to an existing household demand and check what is left.

Service	Existing	EV charger	Heat pump	Connected	Continuous limit	Spare	Utilisation
100 A	60 A	None	None	60.0 A	80.0 A	20.0 A	75.0%
100 A	60 A	48 A	None	108.0 A	80.0 A	-28.0 A	135.0%
100 A	60 A	48 A	25 A	133.0 A	80.0 A	-53.0 A	166.3%
150 A	70 A	32 A	20 A	122.0 A	120.0 A	-2.0 A	101.7%
200 A	80 A	48 A	25 A	153.0 A	160.0 A	7.0 A	95.6%

A 100 A service cannot take a 48 A charger on top of a typical 60 A household load without either a service upgrade or a load management device that sheds the charger when the house draws heavily. The 200 A row fits, but only barely at 95.6%, which leaves nothing for a future addition. This is a planning tool, not a load calculation to code. Electrical work is life-safety work and is subject to local code and inspection. Use these figures for planning and have a licensed electrician verify anything you intend to build.

A home electrical panel load planner helps you answer a question that stands between many households and electrification: can my existing electrical panel handle an EV charger, a heat pump, an induction range, and other new loads — or do I need an expensive service upgrade first? Panel and service upgrades routinely cost thousands of dollars and can involve the utility, so knowing whether you genuinely need one is worth real money. This tool gives a first-pass estimate by stacking your loads and comparing them against your panel's usable capacity.

The calculation begins by summing your loads in amps: the existing whole-house draw plus each new load you want to add — the EV charger, the heat pump, and any other additions like an induction cooktop or a hot-water heat pump. Adding every nameplate rating together, though, overstates reality, because not everything runs at full power simultaneously. That is what the demand factor captures: a percentage that reflects diversity in how loads actually operate together, echoing the demand factors that electrical codes apply in a formal load calculation. The demand-adjusted figure is then compared against the panel's continuous limit, which for safety is taken as 80% of the service rating — a 200-amp panel is treated as having 160 amps of continuous capacity, following the standard rule that continuous loads should not exceed 80% of a breaker or service rating. The difference is your spare capacity, and the ratio is your utilization.

The strategic insight the source research highlights is that managed charging often makes a panel upgrade unnecessary. An EV charger is usually the single largest new load, but it typically runs overnight when the house is otherwise quiet, and a smart charger or load-management device can throttle or pause charging when other big loads switch on. That means the honest question is rarely 'does the sum of nameplate ratings fit', but 'do the loads that actually run at the same time fit' — and the answer is far more often yes than homeowners expect. Because a real installation must comply with the electrical code and local rules, this planner is a screening estimate only: a licensed electrician must perform a full NEC (or local-code) load calculation before any panel, breaker, or service change. Use it to decide whether that conversation is even necessary, and to see how much headroom managed charging buys you.

The 80% continuous rule

Electrical codes require that continuous loads (those running 3+ hours, like an EV charger or heat pump) not exceed 80% of a breaker or service rating. That's why this planner compares your demand against 80% of the panel rating, not 100% — a 200 A panel gives roughly 160 A of usable continuous capacity. Ignoring that margin is how DIY load estimates end up dangerously optimistic.

Managed charging beats a service upgrade

Because an EV charger is usually the biggest new load and mostly runs overnight, a smart charger or load-management device that pauses charging when other large loads switch on can let you add an EV without upgrading the panel at all. Before quoting a costly service upgrade, an electrician will often propose load management first — it's usually far cheaper.

Frequently asked questions

I have a 200 A panel with 60 A of existing load and want to add a 40 A EV charger, a 30 A heat pump, and 25 A of other loads — does it fit?

That's 155 A connected; at an 80% demand factor that's 124 A of demand against a 160 A continuous limit — about 36 A to spare (77.5% utilization). As entered it fits without a service upgrade, though a licensed electrician must confirm with a full load calc.

What demand factor should I use?

It depends on how much your loads overlap in time. Codes apply diversity factors because a house rarely runs everything at once; something in the 70-90% range is a reasonable planning figure, but the formal NEC calculation uses specific rules per load type. Use a higher factor to be conservative.

Do I really need a 200 A service to add an EV charger?

Often not. Many homes add EV charging to a 100 A or 150 A panel using a lower-amperage charger, off-peak-only charging, or a load-management device that throttles the charger when other big appliances run. Run the numbers here first — a service upgrade is sometimes avoidable and always worth pricing against load management.

Is this the same as an official NEC load calculation?

No. This is a simplified screening estimate to tell you whether a full calculation and an electrician visit are worth pursuing. A real load calculation follows NEC Article 220 (or your local code), accounts for each load type's specific rules, and must be done by a qualified electrician before any work.