Quick answer
Electrical Load An electrical load is any device or circuit that draws electric power, from a light bulb to a heat pump; a home's load is the total of them at any moment.
Load is measured two ways: instantaneous demand in watts or kilowatts, and consumption over time in kilowatt-hours. Critical loads are the circuits you choose to keep running from a battery during a grid outage.
Quick facts
The key facts about electrical load, with sources:
- Measured as
- Power (W, kW) and energy (Wh, kWh)
- Daily energy formula
- Watts × hours ÷ 1,000 = kWh 1
- Average US home load
- 10,791 kWh a year (2022) 3
- Critical loads
- Circuits wired to run on battery in an outage
- Battery limits to check
- Continuous kW, motor-start (LRA), usable kWh 4
Key takeaways
- A load is anything that uses power. Your home’s load changes all day.
- Load has two numbers: kW right now, and kWh over time.
- Solar is sized from yearly kWh. Batteries must cover both kW and kWh.
- Motors like pumps and AC compressors surge at start-up, so check a battery’s start rating.
- Critical loads are the few circuits you keep on in a blackout.
Every load has two numbers
A load's power is how hard it pulls right now. Its energy is how much it uses over a day or a month.
Virginia Cooperative Extension's method is the one most calculators use: wattage × hours used per day ÷ 1,000 = daily kWh. The wattage on a nameplate is the power drawn. If only amps are listed, multiply amps by volts.
Solar sizing cares mostly about energy, the kWh you use in a year. Battery backup cares about both. The battery must supply enough kW to run everything switched on at once, and enough kWh to last the outage.
Sources: [1]
How load and solar meet in your home
Solar power goes to the loads in your home first. When the panels make more than the house is using, the extra flows out through the meter to the grid. When the house uses more than the panels make, the grid fills the gap. This all happens on its own, second by second.
So your load shape matters. A home that runs the dishwasher, laundry and pool pump at midday uses more of its own solar.
A home that uses most power after dark exports more by day and buys more at night. How your utility credits those exports decides how much this matters.
The DOE notes that net metering rules depend on your state and utility.
Sources: [6]
Kinds of load a designer looks at
| Load type | What it is | Why it matters for solar or storage |
|---|---|---|
| Base load | The always-on draw: fridge, network gear, standby | Sets the overnight drain on a battery |
| Peak load | The highest kW at once, often an AC compressor or oven | Sets inverter and battery kW |
| Motor (inductive) loads | Pumps, compressors, fans | Start-up surge can trip an undersized battery |
| Critical loads | Circuits chosen for backup | Decide whether partial or whole-home backup fits |
| Phantom loads | Devices drawing power while "off" | Small, constant, and they add up 1 |
Example: a small critical-load list
An illustration built from the published examples in the Virginia Cooperative Extension guide and EIA's light-bulb example. Swap in your own nameplate wattages.
| Load | Watts | Hours per day | kWh per day |
|---|---|---|---|
| Window fan 1 | 200 | 4 | 0.80 |
| Computer and monitor 1 | 270 (120 + 150) | 4 | 1.08 |
| 40 W light bulb 2 | 40 | 5 | 0.20 |
| Total | 510 W if all on at once | 2.08 kWh |
On this list a Powerwall 3, rated 11.5 kW continuous and 13.5 kWh 4, has power to spare and energy for several days before losses.
Real critical-load lists include a refrigerator, well pump or furnace fan, whose motors briefly draw several times their running power on start-up; that surge is why battery sheets list a locked-rotor-amp (LRA) rating, 185 LRA for Powerwall 3. Use the battery sizing calculator with your own appliances.
Where to find your load numbers
- Your bill: monthly kWh and a 12-month history. The US average is about 899 kWh a month 3.
- Appliance nameplates: watts, or volts and amps 1.
- Smart meter data: many utilities show hourly or 15-minute use online. See smart meter statistics.
- Your electrical panel: the breaker labels show which circuits feed which rooms.
- Solar monitoring: some systems add a consumption meter that shows load in real time.
Load compared with related terms
| Term | Meaning | Unit |
|---|---|---|
| Load | Power being drawn now | W or kW |
| Consumption | Energy used over time | kWh |
| Demand | The highest average load in a set interval, used on some tariffs | kW |
| Critical load | Circuits kept on in an outage | W and kWh |
| Battery power rating | The most load a battery can carry | kW |
Partial (critical-load) backup vs whole-home backup
Critical-load backup
- Smaller battery, longer run time.
- Big loads cannot drain the battery by accident.
- Often simpler to fit to an existing panel.
Whole-home backup
- Everything stays on, so no hard choices in advance.
- Needs more battery kW and a plan for large appliances.
- Run time is shorter if you use power as normal.
Limits of load estimates
Nameplate watts are a maximum. Many devices draw less most of the time. A refrigerator cycles on and off, so the Virginia guide suggests dividing its plugged-in hours by three. Estimates from nameplates alone can run high.
Load also changes over the years. An EV, heat pump or new baby changes your kWh and peak kW. Size solar for the load you expect, not only last year’s bills. See solar and EV charging.
Sources: [1]
How load drives cost
Bigger yearly kWh means a bigger solar system. Higher peak kW means a larger inverter or battery. Many motor loads at once may mean a second battery or a load-management device.
Load can also force electrical work. If adding solar, a battery or an EV charger pushes your main panel past its rating, an upgrade may be needed. We do not list prices; see solar cost and the panel upgrade check.
Lifespan: Tesla lists a 10-year warranty on Powerwall 3 4. Panels such as the Qcells series carry 25-year warranties 5.
Building your load list with an installer
- Pull 12 months of kWh from your bills for the solar side.
- For backup, list the circuits you could not do without for two days.
- Read the wattage off each nameplate; for motors, note any LRA or starting current too.
- Estimate hours per day realistically: a refrigerator cycles, so the guide suggests dividing total time plugged in by three 1.
- Hand the list to the installer and ask them to show the kW peak and daily kWh they designed for.
- A licensed electrician moves critical circuits into a backup subpanel if you choose partial backup; the work is permitted and inspected.
Critical loads and the critical-load panel
With partial backup, the installer moves your chosen circuits into a separate subpanel fed by the battery. In an outage only that panel stays on.
It keeps the battery small and the run time long, but you must decide in advance which circuits make the cut.
Our critical-load panel guide walks through how that choice is made, and battery vs generator compares the alternatives.
Whole-home backup skips the subpanel and puts the battery in front of the entire house. That needs more battery power and usually a load-management plan for large appliances.
Keeping load and solar in balance over time
Check your yearly kWh against your solar output once a year. If your load has grown, your bill will show more kWh bought. You may want to shift loads to midday or add panels.
For battery homes, review your critical-load list after any big change, like a new well pump or medical device. Test backup with your installer’s guidance, never by pulling breakers yourself.
Warning signs of an overloaded system
Call your installer or a licensed electrician if you see:
- The battery shuts off when a pump or AC unit starts during an outage.
- Breakers trip when several large loads run together.
- Lights dim sharply when a motor starts.
- Warm breakers, buzzing or a burning smell at the panel.
Safety rule
Moving circuits or adding a subpanel is licensed electrical work. Do not rewire loads yourself.
Rules that apply to loads
Load calculations. NFPA 70, the National Electrical Code, sets how electricians calculate a home’s load and size the service and panel. Your local building department enforces its adopted edition.
Backup equipment. Batteries and their switches carry safety listings. The Powerwall 3 sheet lists UL 9540 and UL 1741, among others. Its Backup Switch is rated 200 A continuous at 120/240 V.
Islanding. When the grid fails, backup systems must isolate the home first so they do not feed the dead grid. IEEE 1547-2018 covers islanding for grid-connected generators.
Common myths about load
- Myth "A big battery can run anything."
- Reality Only up to its kW and start-up limits. Many kWh does not mean many kW.
- Myth "Solar covers my load at night."
- Reality Panels make nothing after dark. Night load comes from the grid or a battery.
- Myth "My load is my bill total."
- Reality The bill shows kWh bought. With solar, some load is met by your panels and never shows up there.
Load and solar rules in SC, GA and VA
Some utilities tie system size to your load. Santee Cooper’s DG-25 rider limits systems to the lesser of 20 kW or your estimated maximum monthly demand 8.
Berkeley Electric sizes systems from your annual kWh ÷ 1,800 or average monthly kWh ÷ 150 9.
In Georgia and Virginia, check your utility’s sizing rule; Virginia law caps residential net metering at 25 kW on investor-owned utilities 10.
When load matters to you
- Sizing solar: use 12 months of kWh.
- Buying backup: list critical loads and their start-up needs.
- Planning an EV or heat pump: add its load before you size.
- Seeing frequent outages: compare partial and whole-home backup.
Related pages
Questions about electrical load
What is a critical load?
A circuit you choose to keep powered from a battery or generator during a grid outage, such as the refrigerator, lights, well pump or medical equipment. Critical loads are usually moved into a dedicated subpanel by a licensed electrician.
How do I calculate my electrical load?
For energy, multiply each appliance's watts by hours used per day and divide by 1,000 to get kWh. For peak power, add the watts of everything that might run at the same time. Your bill gives the monthly total.
What is the difference between load and demand?
Load is the power being drawn at a moment; demand usually means the highest average load over a short interval set by the tariff, which some utility rates charge for separately. Most home rates bill only kWh.
Can a home battery run my whole house?
Sometimes. It depends on whether the battery's continuous kW and start-up rating cover your largest loads together, and whether its kWh last the outage. Many homes use a critical-loads panel instead.
What is a phantom load?
Power drawn by devices that are switched off but still plugged in, like TVs, chargers and game consoles. Each is small, but together they run all day. They add to the base load a battery must carry overnight.
What does LRA mean on a battery?
Locked rotor amps: the surge a motor draws for a moment as it starts. A battery must handle that surge or it shuts off. Tesla lists Powerwall 3 as able to start loads up to 185 LRA.
How much load does an average home have?
EIA puts the average US home at about 10,791 kWh a year in 2022, or 899 a month. Peak load in kW varies far more, from under 1 kW at night to many kW with the AC, oven and dryer on.
Should I size solar for my current load or future load?
Plan for the load you expect over the next few years. Adding an EV or heat pump raises kWh a lot. Check your utility’s size cap first, since some limit system size to past use or demand.
Sources
- Virginia Cooperative Extension, Estimating Appliance and Home Electronic Energy Use (2901-9014, 2020), retrieved .
- US EIA, Electricity explained: Measuring electricity, retrieved .
- US EIA, FAQ: How much electricity does an American home use? (2022 data), retrieved .
- Tesla, Powerwall 3 Datasheet (2024), retrieved .
- Qcells, Q.TRON BLK M-G2+ series data sheet (420–440 W, 2026-02 Rev01 NA), retrieved .
- US DOE Solar Energy Technologies Office, Homeowner’s Guide to Going Solar, retrieved .
- IEEE, 1547-2018 Standard for Interconnection and Interoperability of Distributed Energy Resources, retrieved .
- Santee Cooper, Distributed Generation Rider DG-25, retrieved .
- Berkeley Electric Cooperative, renewable energy (Renewable Surplus Rider), retrieved .
- Code of Virginia §56-594 (net energy metering), retrieved .
Expert review
Written by the HyreSolar Research team. Not yet reviewed by an outside expert. We say so rather than imply a review that has not happened; see our editorial policy.
How the numbers were checked: Load formula, appliance examples and the refrigerator rule from the Virginia Cooperative Extension guide; the bulb example and average use from EIA. Battery limits from the Tesla Powerwall 3 data sheet (re-read 2026-10-08). Utility sizing rules from sc-local/facts.js.
Suggest a correction. We fix errors and say what changed.