Off Grid Solar Load Table
What are off grid solar load tables used for?
The most important part of sizing an off-grid solar system is completing a load table to estimate the amount of energy required per day. A load table lists all the common appliances, the power ratings (wattage) and the average runtime per day. This information is then used to calculate the total daily energy usage in kWh (kilowatt/hours) of a home or business, which is required to size the solar and battery system correctly.
The load table is the first step when designing an off-grid solar system. By using a load table with separate summer and winter load categories, homeowners and businesses can ensure they will get an off-grid system that will meet their energy needs throughout the year.
Benefits of using an off-grid load table:
Helps to accurately estimate the amount of energy used per day (kWh).
Enables the solar array to be sized correctly.
Enables the battery system to be correctly sized to cover periods of bad weather.
Helps to size an off-grid inverter to supply the loads and peak power demands.
If you are considering installing an off-grid solar system, use our off-grid load table to help plan your project and help the designer select the appropriate equipment to meet your needs.
Off Grid Load Calculator Tool
Maximum Demand Explained
Regarding off-grid power systems, the maximum demand is the highest average demand, or load, over a 30-minute period. This is determined by estimating which appliances will be used simultaneously during the highest consumption period. However, this is not always easy to estimate, as each household or business uses different appliances at different times. The total maximum demand is required to select an appropriate off-grid inverter to meet the maximum demand load. If the maximum demand is calculated incorrectly, the selected inverter may be undersized, leading to an overload and system shutdown, causing a blackout.
Summer Vs Winter consumption
Depending on where you live and the local climate, the summer and winter consumption values can vary greatly depending on what appliances are used for heating and cooling, plus hot water. Other high-consumption appliances like EV chargers can also dramatically increase year-round consumption.
Summer - Off-grid solar systems are generally much more reliable in summer as the days are much longer and brighter than in winter. A correctly sized solar system should easily produce enough energy to cover the loads and recharge the battery.
Winter - In contrast to summer, winter consumption in cooler locations is generally much higher due to heating loads, and solar generation is often far lower due to poor weather and shorter days. With this in mind, off-grid solar systems are generally designed and sized around winter consumption and loads.
Off-grid system sizing and energy consumption
The size and cost of an off-grid solar system are directly proportional to the amount of energy the household uses per day. This means the more energy a house uses, the more solar and batteries that will be required to power the home, along with a larger backup generator with longer runtime during poor weather. All this equates to a greater upfront cost. In contrast, a more efficient home will require less solar and a smaller battery. With this in mind, when designing and building an off-grid home, energy efficiency and smart passive solar design should be a top priority, especially in temperate (cooler) climates.
EV charging loads
Charging an EV can require a significant amount of energy depending on how far you drive per day and how often you charge from home. For example, if you only drive short distances — less than 40 km (25 miles) per day — then you might only need to charge once or twice a week, and you could even charge on weekends during the day directly from solar. However, if you need to commute over 100 km (60 miles) daily for work, you may need to charge every night and consume 20 kWh or more per charge. This would almost completely drain an average-size (25 kWh) off-grid battery system and require frequent backup generator use.
Of course, a large off-grid battery system of 50kWh or more storage capacity could cover the EV charging loads as well as the household consumption, but this would also come at a far higher cost and require a large solar array. In summary, EV charging off-grid is possible, but it depends on how far you drive daily and when you are home to recharge. Learn more in the Home EV solar charging explained article.
Frequently Asked Questions
How many kWh does an average off-grid home use per day?
A typical energy-efficient off-grid home uses 15–25 kWh/day. However, consumption varies widely: a small cabin may use as little as 5–8 kWh, while a larger home with heating, cooling, and EV charging can exceed 40 kWh. Completing a load table (above) is the best way to get an accurate estimate for your specific appliances and usage patterns.
How do I size my off-grid solar system from a load table?
Take your highest daily consumption figure (usually winter) and add 20–30% for system losses (inverter efficiency, battery round-trip losses, wiring losses, and days of poor weather). Divide by the average peak sun hours for your location in winter to get the minimum solar array size in kW. For example, 25 kWh/day with 4 peak sun hours and 25% losses = 25 × 1.25 ÷ 4 = ~7.8 kW of solar.
How big should my off-grid battery be?
A common rule is 2–3 days of autonomy: enough stored energy to cover your consumption during consecutive cloudy days without a generator. For 25 kWh/day, that's 50–75 kWh of usable battery capacity. Lithium batteries can be discharged to 80–90% depth, so the nameplate capacity would be slightly higher. A backup generator reduces the required battery size significantly.
What's the difference between summer and winter load tables?
Summer and winter loads can differ significantly. In cool climates, winter heating loads increase consumption dramatically, while summer may add air conditioning loads. Off-grid systems are typically sized for winter because solar generation is lowest and consumption is often highest — if the system covers winter, it will comfortably handle the rest of the year.
Can I use this for a grid-connected system?
Yes — understanding your daily energy consumption is useful for any solar system, not just off-grid. For grid-connected systems, the load table helps you choose the right system size to maximise self-consumption and minimise grid imports. Try the Photonik design tool to model a complete grid-connected system with batteries, tariffs, and financial analysis.