Quick answer
Battery Power Rating A battery power rating is the most electricity a battery can deliver at one moment, measured in kilowatts (kW) or kilovolt-amperes (kVA). Continuous power is what it can sustain; peak power is a higher level it can hold only for seconds, to start motors.
It decides which appliances can run together during an outage, while capacity decides for how long.
Quick facts
The key facts about battery power rating, with sources:
Key takeaways
- Power rating is how much a battery can supply at once, in kW or kVA. Capacity (kWh) is how long.
- Continuous power can be held for as long as charge lasts. Peak power lasts only seconds.
- Motors need a surge to start. Compare an appliance's locked rotor amps (LRA) with the battery's rating.
- Charge power matters too: it limits how fast the battery soaks up midday solar.
- Adding units, shedding loads or backing up fewer circuits keeps you inside the rating.
What a power rating means at home
Think of a battery as a water tank with a tap. Capacity is the size of the tank. The power rating is the width of the tap. A big tank with a narrow tap lasts a long time but cannot fill many buckets at once.
NREL defines rated power capacity as the total possible instant discharge, in kW or MW. It is the most the battery can deliver, starting from full 5. The EIA calls the same thing power capacity: the most power a system can deliver on a continuous basis 6.
In an outage, everything on the backed-up circuits adds up against that number. Go over it and the inverter limits output or shuts off to protect itself, however much charge is left.
The four power figures on a data sheet
| Figure | What it means | Published example |
|---|---|---|
| Continuous output power | Power the battery can supply indefinitely while charge lasts. | 3.84 kVA (Enphase IQ Battery 5P) 1; 11.5 kW (Tesla Powerwall 3) 2; 10 kW / 11.5 kVA (FranklinWH aPower 2) 4 |
| Peak output power or current | A higher output for a few seconds, for inrush when motors start. | 7.68 kVA peak; 32 A for 3 s, 25.6 A for 10 s (IQ Battery 5P) 1; 15 kW for 10 s and 25 kW for 1 s (aPower 2) 4 |
| Load start capability (LRA) | Locked rotor amps the battery can supply to start a motor such as an AC compressor or well pump. | 185 LRA (Powerwall 3) 2; 185 A LRA (aPower 2) 4; up to 48 A LRA, "may vary" (IQ Battery 5P) 1 |
| Maximum charge power | How fast it can refill, which limits how much midday solar it can absorb. | 5 kW (Powerwall 3) 2; 8 kW (aPower 2) 4 |
Why power, not capacity, trips most backup systems
NREL defines rated power capacity as the maximum rate of discharge a battery can achieve from full. Exceed it and the inverter limits output or shuts down to protect itself, however much energy is left.
Motors are the usual cause. A compressor or pump draws several times its running current for a moment as it starts. A battery that runs a load comfortably may still fail to start it.
Hence the advice in our battery vs generator comparison: ask for your appliances' locked rotor amps and compare them with the battery's published surge figure.
The inverter sets the limit, not the cells alone. That is why kVA appears on data sheets. kVA is apparent power; kW is real power. For most home loads the two are close.
Sources: [5]
Heat and settings can lower the rating
A power rating is given at set conditions. Tesla says Powerwall 3 output may be de-rated above 40°C (104°F) 2. FranklinWH says the aPower 2 still runs up to 55°C (131°F), but at a derated 5 kW 4.
Some batteries can also be set to a lower rating on purpose. FranklinWH lists settings of 5, 7.6, 9.6 and 10 kW, each paired with a different breaker size from 30 A to 60 A 4. An installer may pick a lower setting to fit a small electrical panel.
Example: will these loads run together?
An illustration with round, assumed appliance loads, set against the IQ Battery 5P's published 3.84 kVA continuous rating. Your appliances' nameplates are the real inputs.
| Load (assumed for the example) | Running watts | Running total |
|---|---|---|
| Refrigerator | 200 W | 200 W |
| Lights and internet router | 300 W | 500 W |
| Microwave in use | 1,200 W | 1,700 W |
| Well pump running | 1,500 W | 3,200 W (under 3.84 kVA 1) |
The running total fits one unit. The pump's start-up surge is the real test: if its locked rotor amps exceed what the battery publishes, it may not start with the microwave on. Two units, or a soft starter fitted by an electrician, are the usual fixes.
Example: how long a full charge takes
Charge power sets the fastest refill. This uses published figures only.
| Battery | Math | Fastest full charge |
|---|---|---|
| Tesla Powerwall 3 | 13.5 kWh ÷ 5 kW max charge 2 | About 2.7 hours |
| FranklinWH aPower 2 | 15 kWh ÷ 8 kW max charge 4 | About 1.9 hours |
Both need that much spare solar the whole time. On a cloudy day, or with the house using most of the output, a refill takes longer.
Where power rating shows up
- Data sheet: continuous output, peak output, load start (LRA) and max charge.
- Quote: the backed-up circuits list. Ask how it was checked against the kW rating.
- Appliance nameplates: running amps and LRA for AC units, well pumps and fridges.
- Permit plans: the breaker size feeding the battery, which follows its rated current 4.
- Grid storage: in MW, alongside MWh, with duration as the ratio of the two 5.
A higher power rating: gains and trade-offs
What it does well
- Runs more loads at once, including central AC on some systems.
- Starts motors without tripping.
- Charges faster from strong midday solar, if charge power is also high.
Limits to keep in mind
Peak figures last seconds. The IQ Battery 5P lists 32 A for three seconds and 25.6 A for ten 1. A load that needs more than continuous power for minutes will still trip it.
The fine print matters. Enphase says its motor-start figure "may vary", and backup is not supported at 208 V single-phase 1. Power also falls as a battery runs low or gets hot. NREL notes that power capacity is measured from a fully charged state 5.
How the power rating affects cost and warranty
In NLR's home battery cost model, the battery inverter is its own line, apart from the battery pack 7. The inverter sets the power rating, so more kW tends to mean more inverter cost. HyreSolar does not print prices without dated quotes.
Higher power can also add wiring costs: a bigger breaker, heavier wire, or a panel upgrade. Ask whether the quote includes these.
Warranties do not usually cap power. They cap capacity and throughput. FranklinWH warrants the aPower 2 for 15 years or 60 MWh 4. Tesla warrants 70% capacity at 10 years 3.
How an installer checks the power rating fits
A licensed electrician or installer does this. You supply the list of what you need.
- List the loads to keep on and read each nameplate for running watts and LRA.
- Add the running loads that could be on together.
- Compare the total with the continuous rating, and the biggest motor's LRA with the battery's load start figure.
- If it does not fit, add a unit, back up fewer circuits, or add load management.
- Size the breaker and wire to the battery's rated current, then file the permit.
How systems raise their power rating
- More units. Power usually scales with units installed; Tesla supports up to four Powerwall 3 units 2.
- Load management. Smart breakers or controllers shed lower-priority loads when demand approaches the limit.
- Backing up fewer circuits. A critical load panel keeps the connected load inside the rating.
Keeping full power available
Keep the unit in a spot that stays within its range. Tesla rates Powerwall 3 from –20°C to 50°C (–4°F to 122°F) 2. Enphase lists a best range of 0°C to 30°C (32°F to 86°F) 1. Shade on a hot wall helps hold the rating.
Keep the system online for firmware updates, and check the app after an outage. Look for overload events. Repeated overloads mean the backed-up loads need a second look.
Warning signs and when to call a pro
- Backup drops out when the AC, well pump or microwave starts.
- The app logs overload or inverter faults.
- Lights dim hard when a motor kicks on.
- Breakers feeding the battery trip or feel warm.
- Call your installer. Do not swap breakers or rewire circuits yourself.
Safety rule
Never upsize a breaker to stop a battery from tripping. The breaker protects the wire. Ask a licensed electrician.
Rules tied to the power rating
Listings. The inverter that sets the power rating is listed to UL 1741, and the full system to UL 9540. Both appear on the Powerwall 3 and aPower 2 data sheets 2 4. Grid-tied units also list IEEE 1547, the US standard for connecting to the grid.
Breaker and wire. The data sheet names the breaker size: 60 A for Powerwall 3, and 30 A to 60 A for aPower 2 depending on its setting 2 4. The electrical code your area adopts sets how that ties into the panel.
Placement. Location rules come from IRC R328 and NFPA 855: up to 20 kWh per unit, 3 feet between units unless UL 9540A data allows less 8. South Carolina enforces the 2021 codes 10.
Power rating vs capacity
Misconceptions
- Myth A bigger kWh battery can run more at once.
- Reality kWh is how long. Only the kW rating decides what runs together.
- Myth The peak figure is what I can use.
- Reality Peak lasts seconds, such as 32 A for three seconds on the IQ Battery 5P 1. Plan on continuous power.
- Myth If it runs the AC, it will start the AC.
- Reality Starting takes a surge. Check the LRA against the battery's load start rating 2.
Power rating in SC, GA and VA
In hot Southeast summers, central AC is often the load people most want during an outage, and it is the one most likely to exceed a battery's rating. Heat can also derate output on a sun-facing wall 2.
South Carolina had the longest outages of any state in 2024, nearly 53 hours per customer 9. Georgia and Virginia utilities set their own interconnection terms; ask yours.
When the power rating matters to you
- You want central AC, a well pump or an electric range on backup.
- You plan whole-home backup rather than a few circuits; see whole-home battery backup.
- You have big midday solar surplus and want to catch it fast.
- Next step: list your must-run loads with nameplate amps, and ask each installer to show the kW and LRA math.
Next steps
- Battery sizing calculatorChecks kW as well as kWh
- Home battery storage
- How to choose an installer
Questions about battery power rating
What is the difference between continuous and peak power?
Continuous power can be held as long as the charge lasts. Peak power is higher and lasts seconds; the IQ Battery 5P, for example, lists 3.84 kVA continuous and 7.68 kVA peak, with peak current of 32 A for three seconds. Peak exists to start motors, not to run them.
Can a home battery run central air conditioning?
Only if its surge and continuous ratings cover the compressor's start-up and running load alongside everything else on. Compare the unit's locked rotor amps with the battery's published load start capability before assuming it will. Powerwall 3 and aPower 2 each list 185 LRA, for example.
Is kVA the same as kW?
Not quite. kVA is apparent power; kW is real power. For the resistive and mixed loads in most homes they are close, which is why data sheets list either. FranklinWH lists both for the aPower 2: 10 kW real power and 11.5 kVA apparent power.
Does charge power matter?
Yes, if you want the battery to fill from solar in a few midday hours. Powerwall 3 lists 5 kW maximum charge power, so a full 13.5 kWh charge takes at least about 2.7 hours of strong surplus. FranklinWH lists 8 kW for the 15 kWh aPower 2, a bit under two hours.
What does LRA mean on a battery data sheet?
LRA stands for locked rotor amps. It is the surge current a motor draws in the instant it starts, before it spins up. A battery's load start rating says how much of that surge it can supply. Match it against the LRA on your AC unit's or pump's nameplate.
How do I get more power from a home battery system?
Add another unit, since power usually scales with the number installed. Or reduce what runs at once with load management or a critical load panel. An electrician can fit a soft starter to some motors to cut their surge. Never upsize a breaker to stop trips.
Why does my battery shut off with charge left?
Most often, the loads asked for more power than the rating allows, so the inverter shut down to protect itself. A motor starting is the usual trigger. Heat can also lower the rating. Check the app for an overload event, then ask your installer to review the backed-up loads.
What is a good power rating for a home battery?
One that covers the loads you want running together, plus the surge of the largest motor. A few lights and a fridge need far less than central AC. Published continuous ratings range from 3.84 kVA for one IQ Battery 5P to 11.5 kW for one Powerwall 3.
Sources
- Enphase Energy, IQ Battery 5P data sheet (DSH-00010-11.0-EN-2025-05-06), retrieved .
- Tesla, Powerwall 3 Datasheet (2024), retrieved .
- Tesla, Powerwall Limited Warranty (USA), effective 21 August 2023, retrieved .
- FranklinWH, aPower 2 data sheet (2025), retrieved .
- NREL, Grid-Scale Battery Storage: Frequently Asked Questions (NREL/TP-6A20-74426, 2019), retrieved .
- US EIA, Energy storage for electricity generation, retrieved .
- National Laboratory of the Rockies (NLR, formerly NREL), Annual Technology Baseline 2024: Residential Battery Storage, retrieved .
- UL, 2021 Residential ESS Requirements (IRC R328 and NFPA 855 Chapter 15 summary, 2021), retrieved .
- US EIA, Today in Energy: Hurricanes in 2024 led to the most hours without power in 10 years, retrieved .
- SC Building Codes Council, code adoption, 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: Power, surge, charge, derate and breaker figures copied from the Enphase, Tesla and FranklinWH data sheets with their footnote conditions; definition from NREL and EIA; cost structure from the NLR ATB; placement rules from UL's summary of IRC R328 / NFPA 855.
Appliance wattages in the example are labelled assumptions, not measurements.
Suggest a correction. We fix errors and say what changed.