What Size Inverter Do I Need for Home Battery Backup? A 12V, 24V and 48V Sizing Guide
Date:2026-09-26 Click:23
Quick answer: Add up the running watts of everything you want to keep on during an outage, multiply by 1.25, and pick a pure sine wave inverter whose continuous rating meets that number and whose peak rating covers fridge and pump start-up surges. Then size the battery separately: battery Wh ≈ average load watts × backup hours ÷ (usable depth of discharge × 0.9). For home systems of about 2000W and up, a 24V or 48V battery bank is easier and safer to wire than 12V.
How do I work out what size inverter I need for home backup?
The inverter sets how much power you can draw at once, and the battery sets how much energy you have in total. Size the inverter first:
- Step 1: List essential loads (fridge, lights, router, TV, CPAP) and read each device's rated watts from its label.
- Step 2: Add the loads that run at the same time, then multiply by 1.25 for headroom.
- Step 3: Check surge. Refrigerators, freezers and water pumps can briefly draw several times their running power when the compressor or motor starts. The inverter's peak rating must cover the largest start-up surge on top of everything else that is running.
Example: A 150W fridge, 60W of LED lighting, a 20W router and a 100W TV add up to 330W. Multiply by 1.25 to get about 410W continuous. Allowing for the fridge's start-up surge, a 1000W pure sine wave inverter with a 2000W peak, such as the Rogerele 1000W inverter with charger (UPS), handles this with room to spare.
Typical power draw of common household backup loads
These are typical ranges only. Check the label on your own appliance.
| Appliance | Typical running watts | Surge at startup? |
|---|---|---|
| Wi-Fi router / modem | 10–20W | No |
| LED light bulb (each) | 5–15W | No |
| Laptop | 45–100W | No |
| LED TV | 50–150W | No |
| Refrigerator / chest freezer | 100–250W | Yes |
| Well pump / sump pump | 500–1500W | Yes, often large |
How big a battery do I need for my backup time?
Use this formula:
Battery capacity (Wh) ≈ average load (W) × backup hours ÷ (usable depth of discharge × inverter efficiency)
Use your average load, not the peak, because a fridge compressor cycles on and off. LiFePO4 batteries can usually be discharged deeper than lead-acid. Many designers plan on about 80% usable for LiFePO4 and 50% for lead-acid, but check your battery's datasheet.
Example: A 300W average load for 8 hours needs 2400Wh of AC energy. With LiFePO4 at 80% and 90% inverter efficiency, that is 2400 ÷ (0.8 × 0.9) ≈ 3330Wh of nominal battery capacity. You could build it as a 24V 150Ah bank (3600Wh) or a 48V 100Ah bank (4800Wh, which leaves extra margin). Also count the inverter's idle draw, since it runs all night. On the Rogerele REPU-2000, no-load current is under 0.9A at 12V, 0.5A at 24V and 0.3A at 48V.
Should my home battery system be 12V, 24V or 48V?
Higher battery voltage means lower DC current for the same power: thinner cables, less heat and less voltage drop. Estimate current with DC current (A) ≈ AC load (W) ÷ (battery voltage × 0.9):
| Inverter at full rated power | 12V battery | 24V battery | 48V battery |
|---|---|---|---|
| 1000W | ≈ 93A | ≈ 46A | ≈ 23A |
| 2000W | ≈ 185A | ≈ 93A | ≈ 46A |
| 3000W | ≈ 278A | ≈ 139A | ≈ 69A |
| 5000W | ≈ 463A | ≈ 231A | ≈ 116A |
A practical rule is to use 12V for systems up to about 1000W, 24V for 1000–3000W, and 48V for 3000W and above. The battery's BMS continuous discharge rating must exceed these currents, and the inverter's input voltage must match the battery. Rogerele UPS inverters come in DC12V, DC24V and DC48V versions, with input ranges of 10–15.5V, 20–31V and 40–61V.
Which inverter size fits which home backup need?
| Backup goal | Suggested size | Example Rogerele model |
|---|---|---|
| Router, lights, laptop, CPAP | 300–500W | REPU-300 / REPU-500 |
| Fridge + lights + TV + router | 1000–1500W | REPU-1000 (2000W peak) / REPU-1500 (3000W peak) |
| Add a freezer, microwave or small pump | 2000–3000W | REPU-2000 (4000W peak) / REPU-3000 (6000W peak) |
| Larger 220–240V household circuits | 5000W | REPU-5000 (10000W peak, 220/230/240VAC output) |
How does an inverter with charger (UPS) work as home backup?
An inverter with charger (UPS) connects to both the grid and the battery. It charges the battery while grid power is present and runs your loads from the battery when the grid fails. According to the product pages, the Rogerele REPU-2000 and REPU-3000 charge at 30A (12V), 20A (24V) or 10A (48V), and the REPU-5000 charges at 40A on 12V. All of these models output pure sine wave with THD <3% (linear load), and their maximum efficiency ranges from 90% on 12V to 95% on 48V.
Two points to check before you buy:
- Recharge time: At 20A into a 24V 150Ah bank, a full recharge takes roughly 150 ÷ 20 ≈ 7.5 hours or more.
- Battery chemistry: LiFePO4 and lead-acid need different charging voltages. Confirm with the supplier that the charger profile suits your battery. The built-in protection sounds a low-voltage alarm at 10.5V and shuts down at 10V on 12V models (21V/20V on 24V, 42V/40V on 48V).
When should I add solar: a charge controller or a hybrid inverter?
To recharge the battery from solar panels, you have two routes:
- Add a solar charge controller to an existing inverter setup. The Rogerele MPPT solar controller comes in 30A to 60A versions, automatically detects 12/24/48V systems, has an optional lithium battery setting, and lets you customize its charging voltages. Browse all solar charge controllers.
- Choose an all-in-one solar hybrid inverter, which combines the inverter, MPPT charger and AC charger in one unit. The GA series covers 3000–5500W on 24V or 48V batteries and offers an optional transfer time of 10ms for computers or 20ms for home appliances. The RES-3K-65 / RES-6K-65 are rated 3000W and 6000W with an IP65 enclosure.
Sourcing home backup inverters from a factory
Wenzhou Rogerele Electronic Technology Co., Ltd. is an inverter manufacturer in Yueqing, Wenzhou, China. Its range covers pure sine wave inverters, inverters with charger (UPS), solar charge controllers, solar hybrid inverters and inverter PCBA boards. The REPU UPS series carries a 2-year warranty. Distributors and energy-storage brands can contact the Rogerele team for specifications, OEM/ODM options and quotes.
FAQ
What size inverter do I need to run a refrigerator during a power outage?
Most household fridges run at 100–250W but surge at start-up. A 1000W pure sine wave inverter with a 2000W peak is a comfortable minimum for a fridge plus a few small loads.
How many batteries do I need for a 3000W inverter?
It depends on runtime, not just inverter size. Running 3000W for one hour takes about 3300Wh from the battery. For example, a 48V 100Ah LiFePO4 bank (4800Wh) gives roughly one hour at full load. The battery must also supply about 69A continuously at 48V.
Can I use a LiFePO4 battery with an inverter charger?
Yes, provided the inverter's input voltage matches the battery and the charger's voltage settings suit LiFePO4. Confirm the charging profile with the manufacturer before you connect.
Is a 48V battery better than 12V for home backup?
For systems of 3000W and above, usually yes. A 48V system draws a quarter of the current of a 12V system at the same power, which means smaller cables and less heat.
Can an inverter power my whole house?
Only if its continuous and peak ratings cover everything running at once. Most homes back up a critical-loads circuit instead of large loads such as water heaters or central air conditioning.
