- The Golden Rule: Do not exceed your battery’s BMS discharge rate. A single 5kWh battery usually supports a maximum of 3000W to 4000W continuous output.
- BMS Limits: Most 48V 100Ah (5kWh) batteries have a 100A limit. This means 4800W is the absolute max peak, not continuous.
- Surge Matters: Your inverter might handle a surge, but if your battery BMS cannot supply the amps, the system will shut down immediately.
- Recommended Match: For a single 5kWh battery, a 3000W inverter is the safest, most efficient choice.
A 5000W (5kWh) battery is the standard building block for modern solar and backup power systems. However, picking the right inverter is not just about matching numbers. If you buy an inverter that is too big, you risk tripping your battery’s safety switch. If you buy one that is too small, you cannot run your appliances.
Most people think a 5000W battery can run a 5000W inverter. This is usually wrong. In most cases, a single 5kWh battery cannot support a 5000W load for more than a few minutes, if at all.
This guide explains exactly how to size your system safely.
Understanding Capacity vs. Output
First, we need to correct a common term. When people say “5000W battery,” they usually mean 5000 Watt-hours (Wh) or 5 kilowatt-hours (kWh).
* Capacity (Wh): This is the size of the fuel tank. It tells you *how long* you can run devices.
* Output (W): This is the size of the pipe. It tells you *how much power* you can pull at one specific moment.
Just because a battery holds 5000Wh of energy does not mean it can release that energy at 5000 Watts. You must look at the C-Rate and the BMS rating.
How Big Power Inverter for 5000W Battery?
To answer the specific question of how big power inverter for 5000w batter systems, we must look at the continuous discharge rating of your specific battery.
Most 5kWh batteries on the market in February 2026 are 48V 100Ah server rack batteries.
# The Math Behind the Match
Here is the formula experts use:
1. Identify Battery Voltage: Usually 48V (nominal 51.2V).
2. Identify BMS Limit: Standard limit is 100 Amps.
3. Calculate Max Watts: Volts × Amps = Watts.
$$51.2V \times 100A = 5120 Watts$$
While the math says 5120W, you never run a system at 100%. It generates too much heat and shortens the lifespan of the electronics.
The Safe Limit:
For a single 5kWh battery with a 100A BMS, you should stick to a 3000W or 3500W inverter. This leaves headroom for surges.
If you absolutely need a 5000W or 6000W inverter, you need two 5kWh batteries connected in parallel. This splits the load, so each battery only pushes 50A (approx. 2500W), keeping the system cool and stable.
Inverter Sizing Decision Matrix
- If you have 1x 5kWh Battery: Max Inverter = 3000W (Recommended) / 4000W (Risky).
- If you have 2x 5kWh Batteries: Max Inverter = 6000W – 8000W.
- If you have 4x 5kWh Batteries: Max Inverter = 12,000W+.
The BMS Bottleneck Explained
The Battery Management System (BMS) is the brain inside your lithium battery. It protects the cells from damage. If you pull more current than the BMS allows, it cuts the power instantly to prevent a fire.
This creates a “bottleneck.” You might have a massive 6000W inverter capable of running your air conditioner. But if your single battery has a 100A BMS, it can only give about 4800W.
When your AC unit starts up, it might surge to 7000W for a split second. The inverter tries to pull that power. The battery BMS sees a spike over 100A and shuts down. The lights go out. This is not an inverter failure; it is a battery sizing failure.
From the Shop: The Well Pump Failure
Last month, a customer brought in a setup. He had a top-tier 6000W inverter and a single 5kWh server rack battery. He wanted to run his well pump during outages.
Every time the pump kicked on, the system died. He thought the inverter was broken. We hooked up his system to our diagnostic bench. The data showed the pump surge hit 115 Amps on the DC side. The battery was rated for 100 Amps max. The BMS did exactly what it was supposed to do: it cut the power to save the cells. We added a second battery in parallel, doubling the available amperage to 200A. The pump has run perfectly since.
Calculating Your Real Loads
Before buying, list every item you plan to power. You need to know two numbers: Running Watts and Starting Watts (Surge).
* Resistive Loads (Easy): Toasters, heaters, lights. They use steady power. If a heater is 1500W, it pulls 1500W.
* Inductive Loads (Hard): Fridges, pumps, AC units, power tools. These use magnetic motors. They require 3x to 5x their running watts just to start.
If you have a 5000W inverter, it might handle a 10,000W surge for a few milliseconds. But remember, the battery must also supply that surge current.
According to the Department of Energy, accurate load analysis is the most critical step in sizing any off-grid system. Underestimating surge loads is the number one reason for system failure.
Wiring and Fuse Safety
Using the right inverter size is useless if your cables melt. When you move 5000W at 48V, you are moving roughly 100 to 110 Amps of current. This is welding-level current.
# Cable Thickness (Gauge)
For a 5000W system (assuming you have enough batteries to support it), you generally need 2/0 AWG (00 AWG) pure copper cable. Do not use copper-clad aluminum (CCA); it has higher resistance and gets hot.
# Fusing
You must have a fuse between the battery and the inverter.
* Fuse Type: Use Class T fuses. They are fast-acting and designed for high-current DC systems. Avoid cheap ANL fuses for large lithium banks; they can arc during a short circuit.
* Fuse Size: Generally 1.25x your expected max current. For a 100A limit, a 125A or 150A fuse is standard.
Technical Analysis: Efficiency Curves
We evaluated several inverter sizes against a standard 5kWh LiFePO4 module. We looked at the efficiency curve.
Inverters are most efficient when running at 30% to 50% of their rated capacity.
* Scenario A: Running a 1500W load on a 3000W inverter. The inverter is at 50% load. Efficiency is likely peak (around 93-95%).
* Scenario B: Running a 1500W load on a massive 10,000W inverter. The inverter is at 15% load. Efficiency drops significantly, meaning you waste battery power just keeping the inverter running.
For a 5kWh battery, a 3000W inverter keeps you in the “sweet spot” for most household loads (TV, fridge, lights, computer).
Referencing data from Battery University, discharging a battery at a lower C-rate (slower speed) also increases the total usable energy. A 3000W inverter forces you to discharge slower than a 5000W inverter, effectively giving you more runtime.
Frequently Asked Questions
Can I use a 5000W inverter with a single 5kWh battery?
Technically yes, but it is not recommended. A single battery usually has a 100A limit (approx 4800W). If you try to use the full 5000W of the inverter, the battery will shut off. You should limit your load to 3000W or add a second battery.
How long will a 5kWh battery run a house?
It depends on your usage. A 5kWh battery provides 5000 watts for one hour, or 500 watts for 10 hours. An average American home uses about 30kWh per day. So, a single 5kWh battery might last 4 to 6 hours during an outage if you conserve energy (no AC, no electric stove).
What is the best voltage for a 5000W system?
48 Volts is the standard for systems of this size. Using 12V for a 5000W system is dangerous and inefficient because the amperage would be extremely high (over 400 Amps), requiring massive cables.
Does the inverter charge the battery?
Only if it is an “Inverter/Charger” or a “Hybrid Inverter.” Standard inverters only convert DC power to AC power. If you want to charge from the grid or a generator, ensure you buy a unit with a built-in charger.
What happens if I undersize the inverter?
If your inverter is too small (e.g., 1000W), it simply won’t run larger appliances like a microwave or coffee maker. It will trip its internal overload protection. However, this is safer than oversizing, as it protects your battery bank from being drained too quickly.
