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How much power does your property really need?
Chat with Bowie for a few minutes. You'll get your daily kWh, a full appliance list and a report our off-grid engineers use to size your panels and battery.
Where should we send your report?
Once Bowie has your load list, we'll email the full breakdown. A regional off-grid specialist reviews every submission and can recommend panel, inverter and battery sizes for your site.
Sizing an off-grid system starts with one number: your daily kWh
Sizing an off-grid solar system correctly requires knowing your total daily energy consumption in kilowatt-hours (kWh). Too small and you run out of power on cloudy days; too large and you pay for capacity you never use.
Getting the load right first is how we have designed off-grid systems that last since 1987. Here is how the calculator gets you there.
Typical appliance wattage in Australian homes
Use this table to cross-check the values Bowie estimates, or to work out your daily kWh by hand.
Figures are typical averages. Actual consumption varies by model, usage pattern and climate. The AI calculator adjusts estimates based on your specific answers.
| Appliance | Watts | Hours/day | kWh/day |
|---|---|---|---|
| Refrigerator (medium, frost-free) | 150 W | 8 h | 1.2 |
| Split-system air conditioner (2.5 kW) | 850 W | 6 h | 5.1 |
| LED lights (whole house, 10 bulbs) | 100 W | 5 h | 0.5 |
| Electric hot water system (heat pump) | 500 W | 3 h | 1.5 |
| Washing machine | 500 W | 1 h | 0.5 |
| Chest freezer | 80 W | 8 h | 0.6 |
| Television (55" LED) | 80 W | 4 h | 0.3 |
| Laptop computer | 45 W | 6 h | 0.3 |
| Water pump (pressure pump) | 750 W | 1 h | 0.75 |
| Pool pump (0.75 kW) | 750 W | 6 h | 4.5 |
| EV charger (Level 2, 7.4 kW) | 7,400 W | 2 h | 14.8 |
| Microwave oven | 1,200 W | 0.3 h | 0.4 |
Rather talk it through with a person?
Our off-grid team in Nimbin has been designing systems for remote properties since 1987.
Off-grid solar calculator: frequently asked questions
A solar load calculator helps you estimate your daily electricity needs before designing an off-grid or hybrid solar system. It identifies your major energy consumers, air conditioning, water heating, pool pumps, fridges and lighting, and calculates how many kilowatt-hours you consume every day. This figure is the foundation of every solar system design.
What is a solar load calculator?
A solar load calculator estimates your total daily electricity consumption by listing all your appliances, their wattage, and hours of use per day. The resulting kWh figure is used to correctly size solar panels and battery storage for an off-grid or hybrid system.
How do I calculate how many solar panels I need?
Divide your daily energy consumption (kWh) by the average peak sun hours for your location, typically 4 to 5 hours in Australia. Add 20 to 25% for system losses. For example, a home using 10 kWh/day at 5 peak sun hours needs at least 2.5 to 3 kW of solar panels.
What size battery do I need for an off-grid solar system?
Multiply your daily kWh usage by the number of days of autonomy you want, usually 2 to 3 days, then divide by the battery's usable depth of discharge: 0.8 for lithium, 0.5 for lead-acid. A home using 10 kWh/day with 2 days autonomy needs approximately 25 kWh of lithium battery capacity.
What is the difference between off-grid and hybrid solar?
An off-grid solar system operates completely independently from the electricity grid, relying entirely on solar panels and battery storage. A hybrid solar system includes solar panels and batteries but remains connected to the grid as a backup, allowing you to both store excess energy and draw from the grid when needed.
How accurate is this solar load calculator?
This calculator uses AI to identify your appliances and apply typical wattage figures based on your descriptions. Accuracy depends on how completely you describe your appliances and usage habits. The results are estimates suitable for initial planning. Rainbow Power Company's engineers review every submission and can refine the design for your specific situation.
Is this calculator free to use?
Yes. The Off-Grid Solar Load Calculator is completely free. After the chat, you receive a personalised energy report by email at no cost. There is no obligation to purchase anything.
Why is load estimation important for solar system design?
Accurate load estimation prevents undersizing, which causes power shortages, and oversizing, which wastes money. Knowing your exact daily kWh consumption lets engineers select the right number of solar panels, the correct inverter size, and sufficient battery capacity to meet your needs reliably.
Learn more about off-grid systems at Rainbow Power Company, Australia's off-grid solar specialists since 1987.
