Off-grid battery sizing guide
What size battery do I need for off-grid?
The honest answer is: it depends on what you want the system to survive. A weekend cabin, a normal family home, a workshop, and a full off-grid property all need different answers, especially in winter when the days are shorter and solar production is lower.
Start with lifestyle
Off-grid design starts with what matters to you. Do you need everything to run normally through bad weather, or are you happy to manage heavy loads during cloudy periods?
Size for winter
Summer can make almost any solar system look good. Winter is where the truth shows up: shorter days, lower sun angle, more cloudy periods, and higher heating loads.
Do not chase false precision
A calculator helps, but it is still an estimate. Sometimes the better decision is to oversize the battery bank a little instead of spending weeks trying to calculate every kettle boil.
Not sure where to start?
Use the quick Battery & System Finder first. It works like a guided intake: one question at a time, with extra questions only when they are relevant to your situation.
After that, the calculator below can help you sanity-check the battery size and winter reserve.
What it helps us work out
- Whether you need off-grid, rebate, DIY, or installed-system advice.
- Whether the LifePro 16kWh EVE-cell battery is a good fit.
- Whether Deye, Victron, Pylontech, Growatt, Sigenergy, GoodWe, or another path makes sense.
- What information we should ask for next.
Learn the simple sizing idea Open this if you want the plain-English method behind off-grid battery sizing.
The simple off-grid sizing idea
A battery bank should cover your overnight use, your cloudy-day reserve, and your real-world losses. The solar array then needs to refill that energy during the worst useful solar season for your location.
For LiFePO4 batteries, using around 80% usable capacity is a conservative planning number. You can sometimes use more, but sizing with headroom helps the battery work easier and gives you margin when the weather is not kind.
Optional battery sizing calculator Open this if you want to estimate daily use, reserve days, 16kWh battery blocks and winter solar size.
Interactive estimate
Off-grid battery sizing wizard
Use this as a planning guide. For the final design, we still want to know your location, appliances, seasonal usage, and what you want the system to survive.
Household appliance estimate
Start with a typical household profile, then adjust the efficiency level, TV size, hours, and quantities. This is much easier than trying to remember every appliance from a blank page.
| Load | Qty | Watts | Hours/day | kWh/day | |
|---|---|---|---|---|---|
| Appliance estimate | 0.0 | ||||
Read the deeper off-grid guide Winter sizing, when oversizing makes sense, and common battery bank sizes.
Why winter changes the answer
In summer, long days and stronger solar production can hide an undersized system. In winter, the battery has to carry more of the home through longer nights and weaker solar days. If the property is in southern Australia, in a valley, surrounded by trees, or has poor panel orientation, the winter number becomes even more important.
This is why two homes using the same daily kWh can need different battery banks. One might have excellent north-facing solar and backup generator support. Another might be shaded in the morning, use electric cooking, run pressure pumps, and need three days of reserve because access is difficult after rain.
When oversizing makes sense
There is a point where chasing perfect calculations becomes less useful than adding sensible headroom. If the system is mission-critical, the property is remote, or the customer wants normal comfort without constantly watching the battery percentage, a larger bank can be the cheaper emotional decision.
- Less generator runtime during bad weather.
- More room for future loads such as pumps, tools, EV charging, or air conditioning.
- Lower daily stress on the battery bank.
- A system that feels easier to live with.
When not to oversize blindly
Oversizing still needs a plan. A big battery with too little solar may take too long to recover. A large inverter without the right battery discharge capability may not support heavy surge loads. The goal is not just a huge number; it is a balanced system.
- Battery capacity should match solar recovery.
- Inverter size should match peak and surge loads.
- System voltage and current should keep wiring practical.
- Install requirements should be considered early.
Common off-grid battery sizes
| Battery bank | Typical use | Best suited to |
|---|---|---|
| 10-16 kWh | Light cabin, careful tiny home, essential loads, or small off-grid setup. | Fridge, lights, internet, water pump, modest appliance use. |
| 30-35 kWh | More comfortable off-grid home with useful winter reserve. | Normal home loads with some load management and sensible solar size. |
| 45-65 kWh | Family home, larger property, or customers who want fewer compromises. | More winter autonomy, pumps, tools, larger daily consumption. |
| 80 kWh+ | Large homes, commercial loads, workshops, serious energy independence. | High daily kWh, heavy loads, or longer no-sun reserve targets. |
Frequently asked questions
Is 16kWh enough for an off-grid house?
It can be enough for a careful home, cabin, or efficient setup, especially with good solar and backup generation. For a normal family home that wants comfort through winter, 16kWh is often a starting point rather than the final answer.
How many days of battery reserve should I choose?
Two days is a practical starting point for many off-grid homes. Three days is more comfortable in winter, remote locations, or places where generator use is inconvenient. One day can work for budget systems, but it needs more lifestyle management.
Should I size from my electricity bill?
Your bill is useful if the home already exists and the usage pattern will be similar. For a new off-grid home, appliance estimates and lifestyle questions are more important. Heating, cooking, water pumps, bore pumps, refrigeration, and workshop loads can change the answer quickly.
Why does solar size matter when I am asking about battery size?
The battery carries you through the night and bad weather. The solar array has to refill it. If the battery is large but solar is too small, the system may not recover properly in winter.
Can I add more batteries later?
Often yes, but it depends on the battery model, inverter, BMS compatibility, installation layout, and age of the existing battery bank. If expansion is likely, it is better to design for that from the start.
Ready to send the full details?
If you already have photos, plans, meter box images, or an appliance list, open the detailed site form. Otherwise, the quick finder above is enough to start.
Open detailed site formDetailed site evaluation form Open this when you are ready to upload photos and give us the technical site details.
Off-grid system enquiry
Tell us what you are trying to run, where the property is, and how much reserve you want. Photos, plans, meter box images, and appliance lists are very helpful.