How Long Will a 10 kWh Battery Last?

A 10 kWh home battery lasts about 7.2 hours at a steady 1,000 W when you use realistic settings—80% depth-of-discharge and 90% system efficiency.
Formula: Runtime (hours) = 10,000 Wh × DoD × Efficiency ÷ Average Load (W)

Nameplate vs. realistic runtime

Average Load	Nameplate 10 kWh	Realistic (80% DoD, 90% eff.)
500 W	20.0 h	14.4 h
1,000 W	10.0 h	7.2 h
2,000 W	5.0 h	3.6 h

How does the 10 kWh battery runtime calculation work?

Step-by-step, with units you can follow even if you’re brand new:

1. What is “usable energy”?
   Not all of the 10,000 Wh is meant to be drained. We pick a safe Depth of Discharge (DoD) and include typical system losses.
   Usable_Wh = 10,000 × DoD × Efficiency
   Example (80% DoD, 90% eff.): 10,000 × 0.8 × 0.9 = **7,200 Wh**.
2. What is your average load?
   Add up the watts of the things running on average (a fridge might be 120 W but only 30% of the time → 36 W average).
3. How long will it run?
   Runtime (hours) = Usable_Wh ÷ Average_Load_W
   Example at 1,000 W: 7,200 ÷ 1,000 = **7.2 hours**.

What affects how long a 10 kWh battery will last?

• Why does Depth of Discharge matter?
  Deeper cycles give longer runtime today but reduce lifespan over many years. LiFePO4 (LFP) is happy around 70–90% DoD for daily cycling.
• What efficiency should I assume?
  Inverter + wiring + DC/AC losses typically land you near 85–92% overall. We use 90% for planning.
• Why do temperature and surge change the answer?
  Cold reduces available capacity; motors (AC, pumps) draw a high start surge, which may trip undersized inverters and raise average load.
• Does “idle” power matter?
  Yes—many inverters draw 10–40 W even with no load. Include it in your average.

How long will 10 kWh last for common home appliances?

Assumptions: 80% DoD, 90% efficiency → 7,200 Wh usable. Duty cycle = how often it actually runs.

Appliance (example use)	Typical W	Duty Cycle	Avg W	Runtime on 10 kWh (realistic)
LED lights (10 × 10 W)	100	100%	100	72 h
Wi-Fi router + ONT	12	100%	12	600 h
Laptop working	60	100%	60	120 h
TV (55″)	120	100%	120	60 h
Refrigerator (modern)	120	30%	36	200 h
CPAP (no humidifier)	60	100%	60	120 h
Well/sump pump	700	10%	70	103 h
Microwave (intermittent)	1,000	5%	50	144 h
Window AC (small room)	900	50%	450	16 h
Split AC (½–1 ton, efficient)	1,200–1,500	50%	600–750	9.6–12 h
Space heater (resistance)	1,500	100%	1,500	4.8 h

Tip: AC and electric resistance heaters eat energy fast. Cooling/heating with high duty cycles is the #1 reason a “10 kWh lasts all night” claim fails.

Does a 10 kWh battery power a whole home?

Short answer: It depends on your average draw.

Home style	Typical Avg Load	Realistic Runtime
Tiny/Efficient cabin	300–400 W	18–24 h
Efficient 1-bed apartment	600–800 W	9–12 h
Average 3-bed house (no AC)	900–1,200 W	6–8 h
Average 3-bed (with AC cycling)	1.5–2.5 kW	2.9–4.8 h

Plan for essentials (lights, fridge, Wi-Fi, a few outlets) and you’ll get strong overnight coverage. Add AC or resistance heat and runtime collapses.

How do you size runtime properly?

Below is the same 5-step method, but written like a recipe. Grab a pen or a spreadsheet.

Step 1 — Make a simple load list (we’ll turn watts into “average watts”)

1. Write each thing you want to power (e.g., fridge, lights, Wi-Fi, TV, laptop).
2. Find each item’s watts (W). It’s on the label; if not, quick-search “device model + watts.”
3. Estimate how often it actually runs (duty cycle).
   • Always on = 100% (Wi-Fi, lights you’ll keep on).
   • Sometimes on = 10–60% (fridge ~30%, well pump ~10–20%, AC often ~50%).
4. Convert to average watts: Average W = Watts × Duty Cycle.
   • Example: Fridge 120 W × 0.30 = 36 W average.

Cheat sheet for duty cycle (typical):
fridge 25–35%, sump/well pump 10–20%, TV 50–80% while in use, split AC 40–60% in mild weather, LED lights 100% when on.

Step 2 — Add up your average watts (don’t forget inverter idle)

• Total_Avg_W = sum of all Average W + inverter idle.
• Inverter idle is the “just sitting on” draw (often 10–40 W). If you don’t know, use 20 W.
• Example list → lights 100, Wi-Fi 12, laptop 60, TV 120, fridge 36, inverter idle 20 → Total_Avg_W = 348 W.

Step 3 — Pick safe settings for the battery math

• Depth of Discharge (DoD): how much of the 10 kWh we plan to use. Use 80% for daily cycling.
• System Efficiency: losses in inverter/wiring. Use 90% unless you know better.
• These two turn 10,000 Wh into what’s actually usable today:
  Usable_Wh = 10,000 × DoD × Efficiency = 10,000 × 0.8 × 0.9 = **7,200 Wh**.

Step 4 — Calculate runtime (and sanity-check with a range)

• Core formula: Runtime (hours) = Usable_Wh ÷ Total_Avg_W.
• Example with our 348 W: 7,200 ÷ 348 = **20.7 hours**.
• Range check:
  • Best-case (nameplate, no losses): 10,000 ÷ 348 = 28.7 h.
  • Conservative (DoD 70%, eff. 85% → 5,950 Wh): 5,950 ÷ 348 = 17.1 h.

Step 5 — Stress-test with “what ifs” (this is where plans fail or succeed)

• Add a big load for 1–2 hours: e.g., microwave 1,000 W for 15 min (0.25 h) → 250 Wh extra.
• Turn on a room AC: If average +300 W for the evening, new Total_Avg_W = 648 W → 7,200 ÷ 648 = 11.1 h.
• Cold night: knock 10–15% off usable Wh (batteries give less in the cold). 7,200 × 0.9 = 6,480 Wh.

If your “stress-tested” runtime still covers the night, you’re sized well. If not, shorten the load list, add PV, or increase battery size.

What about recharging—how many solar panels do you need?

Rule of thumb:
Daily Solar kWh = Array_kW × Peak Sun Hours × 0.80

Example: 3 kW array, 5 PSH, 0.80 losses → 3 × 5 × 0.8 = 12 kWh/day.
That can refill a 10 kWh battery in one good day if the home isn’t using most of that energy during daylight. If you consume 6 kWh during the day, only ~6 kWh remains to charge the battery—so ~2 days to fill from empty.

Typical arrays to refill 10 kWh from empty (ideal sky):

Array Size	4 PSH	5 PSH	6 PSH
2 kW	6.4 kWh/day	8.0 kWh/day	9.6 kWh/day
3 kW	9.6 kWh/day	12.0 kWh/day	14.4 kWh/day
5 kW	16.0 kWh/day	20.0 kWh/day	24.0 kWh/day

If you want the battery full every evening, size PV so “Daily Solar kWh – Daytime Use ≥ 10 kWh.”

Why do people mention the “20–80% rule,” and does it apply to LiFePO4?

You’ll often hear: “keep lithium between 20% and 80%.” It’s not a hard law, it’s a longevity habit. Lithium cells dislike sitting at the extremes for long periods. Near 0%, voltage sags and protection trips; near 100%, cells are tightly packed with charge and a bit more chemically “stressed,” especially if kept hot. Cycling in the middle band reduces stress and heat, and usually extends lifespan.

For LiFePO4 (LFP)—the chemistry most home batteries use—this rule is softer than for other lithium chemistries. LFP is very stable, so daily operation at 70–90% DoD (i.e., using 70–90% of the battery each cycle) is common and safe. The bigger wins for LFP life are:

• Avoid parking at 100% SoC for days. It’s fine to fill to 100%; just don’t leave it there long-term.
• Avoid deep over-discharge. Let the inverter cut off before the pack is truly empty.
• Keep temperatures reasonable. Room-temperature operation is kind to cells.
• For storage (weeks–months): leave 40–60% SoC and disconnect heavy loads.

So: use the energy you need, but don’t live at the edges unless you must. That gets you most of the “20–80%” benefit without obsessing over exact numbers.

What inverter size do you need for a 10 kWh battery?

Think of battery (kWh) as the size of your fuel tank and the inverter (kW) as the size of your engine. The tank answers “how long”; the engine answers “how much at once.” Here’s how to pick an inverter power rating you won’t outgrow:

1) Add up your simultaneous running watts.
List what could be on at the same time (fridge, lights, TV, computers, a small AC). Suppose that totals 1,600 W.

2) Identify your biggest motor surge.
Motors (AC compressors, well pumps) can need 2–3× their running watts for a few seconds.

• Example: a 900 W window AC may surge to 2,000–2,700 W at start.

3) Choose continuous and surge ratings that clear both.
Pick an inverter whose continuous kW exceeds your simultaneous running watts with headroom (20–30%), and whose surge rating comfortably clears the biggest motor start.

• With 1,600 W running and a 2,700 W surge, a 3–4 kW hybrid inverter (often 6–8 kW surge) is a safe, quiet choice.

4) Match voltage and chemistry.
Most 10 kWh systems are 48 V LiFePO4 packs paired with a hybrid inverter/charger (solar + grid + battery). Keep DC voltage and BMS communications compatible.

5) Plan for the near future.
If you think you’ll add a second small AC or power tools, skip the edge case and size to 5–6 kW. It costs less than replacing an undersized inverter later.

Quick picks by home pattern (guidance, not a rule):

• Essentials only (lights, fridge, IT): 3–4 kW inverter is ample.
• One small AC zone + essentials: 4–6 kW.
• Multiple zones or big well pump: 6–8 kW (and verify surge spec is ≥2–3× your toughest motor).

Final check: your inverter power (kW) doesn’t change battery energy (kWh). It just ensures the system can deliver that energy at the rate your home demands—without tripping on surges.

How can you quickly estimate your runtime

Use these defaults if unsure: DoD = 80%, Efficiency = 90%.

1. Add up average watts for what you’ll run (include inverter idle).
2. Compute: Runtime = (10,000 × DoD × Efficiency) ÷ Avg_W.

Examples (realistic 7,200 Wh usable):

• Essentials set (lights 100 + fridge 36 + router 12 + laptop 60) = 208 W → 34.6 h
• Two rooms lit (200 W) + TV 120 + fridge 36 + router 12 + fans 100 = 468 W → 15.4 h
• Small window AC (450 W avg) + basic essentials (150 W) = 600 W → 12.0 h

FAQs

Q: Is a 10 kWh battery enough to run a house overnight?
A: Yes for essentials (lights, fridge, Wi-Fi, electronics). With AC or electric heating, expect shorter runtimes (3–8 h depending on size/duty).

Q: Can a 10 kWh battery run air conditioning?
A: Usually yes for a small room unit or efficient split on a hybrid inverter sized for surge. Expect 9–12 h at moderate duty for a single small zone.

Q: Is it bad to keep a lithium battery at 100%?
A: Occasional full charges are fine; don’t park at 100% for days. For longevity, daily cycle within 20–95% SoC and store around 40–60%.

Q: How many solar panels to recharge 10 kWh daily?
A: Roughly 3–5 kW of PV in 5–6 PSH regions, depending on your daytime consumption.

Q: What if my fridge or pump has a big start surge?
A: Size the inverter for 2–3× the running watts. Surge doesn’t change kWh much, but an undersized inverter can trip.

What should you do next?

• List your essentials, estimate average watts, and compute a first-pass runtime with the formula above.
• If you want help choosing the right inverter + battery + PV so your 10 kWh truly lasts the night, we can size it from your loads and sun hours.

Assumptions & notes

• We treat “10 kWh” as nameplate; real-world usable energy depends on DoD and system efficiency.
• Examples use LiFePO4 chemistry (common in home storage) and grid-quality inverters.
• Your results vary with climate, appliance mix, charging profile, and wiring quality.

Need a precise plan? Share your appliance list and city—we’ll reply with a tailored runtime + recharge sizing.