First, Understand Your Daily Electricity Use
You cannot size a battery without knowing how much power you use. This is like buying a suitcase without knowing how long your trip is.
Grab your electricity bill. Look for the number in kilowatt-hours (kWh). That is your monthly usage. Divide by 30 to get your average daily usage.
Here are some real-world examples based on recent customer data from Southeast Asia and Europe:
Small apartment (1-2 people, no AC, gas stove): 8 to 12 kWh per day
Medium house (3-4 people, AC in bedrooms, electric appliances): 15 to 25 kWh per day
Large house (4+ people, central AC, EV, pool pump): 30 to 50 kWh per day
Write down your number. You will need it.
But do not just take the average. Look at your usage pattern throughout the day. Most homes use power in three peaks:
Morning (6-9am): breakfast, showers, getting ready
Evening (6-10pm): dinner, TV, lights, appliances
Night (10pm-6am): minimal usage, mostly standby loads
Solar panels generate power during the day, peaking around noon. Without a battery, any solar power you do not use during the day gets sent to the grid. You buy power back at night. That is inefficient.
A battery shifts your solar power from daytime to evening. That is the basic value proposition.
Two Different Jobs for a Battery
Before you pick a capacity, decide what job you want the battery to do. This changes everything.
Job 1: Backup power
You want the lights to stay on when the grid goes down. Maybe the refrigerator, internet, a few outlets, and some lights. You are not trying to run the whole house. You just want to avoid sitting in the dark.
For backup, you do not need a huge battery. You need enough to cover essential loads for a certain number of hours. A 5kWh battery can run a fridge (150W) for 30+ hours. Add lights, phone chargers, and a router, and you still have plenty.
The key question for backup: How long do outages typically last where you live? If they are usually 2-4 hours, a small battery is fine. If you live somewhere with multi-day outages, you need more capacity or a generator.
Job 2: Peak shaving / arbitrage
You want to save money on your electricity bill. Your utility has time-of-use rates. Power is cheap at night and expensive in the late afternoon and evening.
With a battery, you charge during cheap hours (from the grid or from your solar) and discharge during expensive hours. You avoid buying expensive power.
For this job, the math is different. You want a battery large enough to cover your evening usage. Look at your daily usage between 4pm and 9pm. That is what you want the battery to supply.
If your evening usage is 8kWh, a 10kWh battery gives you some margin. If your evening usage is 3kWh, a 5kWh battery is plenty. A bigger battery just sits partly empty, and you paid for capacity you never use.
Hybrid approach
Most homeowners want both. They want to save money every day, and they want backup for when the grid fails. That is fine. Size for the daily savings job first. Whatever capacity you end up with will also work for backup. The only difference is how many hours of backup you get.
Capacity Tiers: What Each Size Does
5kWh – Entry level
This is for small households or people who just want basic backup.
Daily usage: under 10kWh
Evening usage: 2-4kWh
Backup: covers essentials (fridge, lights, internet) for 10-20 hours
Best for: apartments, small homes, people who just want outage protection
With a 5kWh battery, you can shift your evening peak usage away from expensive grid power. But you will still draw from the grid for heavy evening loads like AC or cooking.
10kWh – Sweet spot
This is what most medium-sized homes need.
Daily usage: 15-25kWh
Evening usage: 5-8kWh
Backup: covers essentials for 24-48 hours, or can run a few circuits for most of a day
Best for: typical 3-4 bedroom homes, families with an EV that charges during the day
A 10kWh battery handles most of your evening usage. You might still pull a little from the grid on high-demand evenings. But your bill will drop significantly. And you have enough backup to get through most outages without thinking about it.
15kWh+ – Large home or heavy user
This is for big houses or people who want to be nearly grid-independent.
Daily usage: 30-50kWh
Evening usage: 10-15kWh
Backup: covers essentials for days, or can run most of the house for 8-12 hours
Best for: large homes, people with medical equipment, those in areas with frequent long outages
At this size, you can run central AC, an EV charger, and appliances all evening from battery. You barely touch the grid during peak hours. But you pay for that convenience. These systems are significantly more expensive.
A note: If your daily usage is over 40kWh, consider whether you really need to store that much. Sometimes it is cheaper to reduce usage than to store it. LED lights, efficient appliances, and better insulation often give better returns than a giant battery.
A Real Example
Let me give you a real example from a customer we worked with in early 2026.
Four-bedroom house in Selangor, Malaysia. Two adults, two kids. Daily usage around 22kWh. Evening usage (5pm to 10pm) around 8kWh. They already had solar panels generating 25-30kWh per day.
They installed a 10kWh battery in February 2026.
Here is what changed:
Before battery: They used solar during the day, but bought grid power from 5pm to 10pm. Monthly bill was about 280 ringgit (roughly $60 USD).
After battery: The battery charges during the day from excess solar. From 5pm to 10pm, the battery powers the house. They buy almost no grid power during peak hours. Monthly bill dropped to about 70 ringgit (roughly $15 USD).
Payback period: About 4 years based on current electricity rates in Malaysia. After that, pure savings.
Could they have used a 5kWh battery? Yes, but they would have run out of stored power around 8pm. The last two hours of evening would have come from the grid. Savings would be lower.
Could they have used a 15kWh battery? Yes, but it would have cost about 50% more. The extra 5kWh would have sat mostly empty. They would never recover the additional cost.
10kWh was exactly right for their usage pattern.
What We Offer at Wenzhou Chuhan (2026)
We make lithium iron phosphate (LFP) batteries for home and small commercial use. LFP is the same chemistry used by Tesla's Powerwall and many other major brands. Here are our current standard sizes:
5kWh – Wall-mounted, about the size of a small suitcase. Good for apartments or basic backup. You can add a second unit to reach 10kWh.
10kWh – Our most popular size in 2026. Wall-mounted or floor-standing. Handles most homes' evening usage. Also expandable.
15kWh – For larger homes. Usually floor-standing. Can be expanded further for near-grid-independent setups.
All our batteries use LFP cells. Here is why that matters in 2026:
Safer chemistry – Much lower fire risk than NMC batteries. This is why LFP has become the standard for home storage.
Longer cycle life – 6,000+ cycles at 80% depth of discharge. That is roughly 15+ years of daily use.
No cobalt – More ethical supply chain and less exposed to price swings.
Lower energy density – Slightly heavier than NMC, but for a wall-mounted home battery, a few extra kilograms do not matter.
Every battery includes a Battery Management System (BMS) that monitors cell voltages, temperatures, and current in real time. The BMS talks to our inverters to decide when to charge and discharge.
Our batteries work with our own hybrid inverters. They can also work with many other brands in AC-coupled setups. If you already have solar and want to add storage, send us your inverter model and we will check compatibility.
How to Decide: A Simple Process
Step 1: Find your daily and evening usage numbers from your electricity bill. If you do not have a bill, check your utility's app or website.
Step 2: Decide your priority – backup, bill savings, or both.
Step 3: If bill savings is your goal, size for your evening usage. Round up to the nearest standard size.
Step 4: If backup is your only goal, size for how many hours you want to run essential loads. For most people, 5kWh is plenty.
Step 5: If you are not sure, start with a 5kWh or 10kWh expandable system. You can always add more later.
Do not let a salesperson talk you into a giant battery you do not need. More capacity is not always better. It is just more expensive.
If you want help with the math, reach out. Send us your electricity bill (you can block out personal information) and tell us what you want the battery to do. We will give you a recommendation.
We sell batteries. But we would rather sell you the right battery than the biggest battery.
