Updated on April 20, 2026
You have three solar energy system quotes sitting on your kitchen bench. One recommends 6.6kW, another suggests 10kW, and the third falls somewhere in between. All three installers seemed confident, but you’re not sure who to trust.
The truth is, any of them could be right or wrong. It all depends on how your household uses electricity.
At PSC Energy, we handle every part of your solar installation ourselves. We size systems based on your real energy use, not a generic template. After installing solar on thousands of homes across Sydney and regional NSW, we’ve learned that every household uses electricity differently.
In this article, you’ll learn about the following:
- What Are Energy Consumption Patterns?
- How to Work Out Your Energy Needs
- Why the Old 6.6kW Solar Panel System Default Is Out of Date (Sometimes)
- The 2/3 Rule: Where to Put Your Panels
- How to Calculate Your System Size
- Future-Proofing Your Solar Energy System
- FAQ: Sizing Your Solar Energy System
By the end of this article, you’ll know how to figure out the right system size for your home.
What are Energy Consumption Patterns?
“Energy consumption pattern” might sound like a term made up by a solar salesperson to sound impressive. Try saying it: energy consumption patterns. It rolls off the tongue easily. It just means how and when your household uses electricity.
Break it down word by word:
Energy is the electricity running your lights, appliances, and hot water system. Pretty straightforward.
Consumption is how much of it you use.
Patterns mean your usage tends to repeat. You probably use electricity at roughly the same times each day, each week, and each season.
When you put these three ideas together, you get a clear picture of how electricity moves through your home each day.
A good solar installer uses this information to size your system correctly.
How Do You Determine Your Energy Needs?
Start with your electricity bill. It shows how many kilowatt-hours (kWh) you used over the billing period. Add up the last 12 months of bills to get your annual figure. You’ll need that number later for the maths section.
Beyond the raw numbers, think through these four areas:
Daily routine. Are you home during the day, or do you leave for work or school in the morning and return in the evening?
Most households in Sydney use electricity in the morning while getting ready, then again in the afternoon and evening for cooking, watching TV, and charging devices.
If you work from home or have young children, your usage pattern will be different from the usual profile.
Appliance usage. Which appliances do you use, and at what times? Air conditioning, electric ovens, dishwashers, washing machines, and pool pumps are major energy users.
A home running the air conditioner from 3pm uses power differently from one that only turns it on at night. Consider which appliances you use and when.
Seasonal changes. Your electricity use changes with the seasons. You’ll use more heating or cooling in summer and winter.
In winter, you’ll need more lighting because the sun sets earlier. A pool pump might run on a timer in summer but stay off in winter.
These changes are part of your usage pattern and affect how your solar system works throughout the year.
Future plans. This is more important than many people think. Are you planning to buy an electric vehicle, add a pool, switch gas appliances to electric, or work from home permanently?
Any of these changes will increase your electricity needs. If you don’t plan for them now, you might face a costly upgrade sooner than expected.
If you’re interested in learning a bit more about how to save with solar, you might want to check out the following article titled, Self-Consumption: How to Increase Solar Energy Use.
How Do Energy Needs Guide Your Solar Purchase?
The more energy you use, the larger the system you’ll need to save money and reduce your reliance on the electric grid. Similarly, the less energy you use, the smaller the system you’ll need.
However, we recommend installing a system that is easily expandable in the future, as electricity needs may change drastically even in the future, as the current energy crisis unfolds.
Families with school-age children will most likely use more energy in the morning than households without children. Kids wake up early and turn everything on. Parents are pretty likely to cook breakfast for kids and themselves, whereas a couple living together might skip turning on the TV and have coffee for breakfast.
Both types of households will undoubtedly use a lot of energy in the evening. The family gets home from school and work and needs electricity to see them through the evening hours just as much as a household without children.
Households with infants, people who work from home, and households with retirees are a different story. If a household has small children and a parent is home all day with them, then the electricity needs will be different throughout the day. The same applies to individuals who work from home and retirees who spend their days at home.
Not long ago, 6.6kW was the go-to recommendation for most Australian households. There was a practical reason for it: a 6.6kW system connects easily to the grid with a 5kW inverter, and network operators were straightforward to deal with on approvals.
A 6.6kW system produces roughly 26kWh of electricity on a good day.
For many households in 2018 or 2019, that was enough.
Today, that’s often not enough. Electricity prices have gone up across Australia, and households are using more power due to working from home, charging electric vehicles, and switching from gas to electric appliances.
Future needs are likely to be even higher. Some solar companies still recommend 6.6kW because it’s simple to sell and install. Be wary of any installer who suggests this size without asking detailed questions about your energy use.
But here’s the reality: a 6.6kW system is still right for some households. If you live alone, use little power, and don’t expect that to change, this size might suit you.
Bigger isn’t always better. If extra capacity just goes back to the grid at a low rate, you may not get your money back quickly.
The main question isn’t “what’s the standard recommendation?” but “what does your household actually need?”
If your installer can’t answer that without knowing your usage, it’s time to look for someone else.
Most households today are better served by systems in the 10kW to 13kW range, but the right size still depends on your individual situation.
If you’re interested in learning why other solar companies recommend a string system, you might want to check out the following article titled, Why Do Companies Sell 6.6kW String Systems with 5kW Inverters?
The 2/3 Rule: Where to Put Your Panels
Most people assume solar panels should go on the north-facing roof.
In Australia, the sun tracks across the northern sky, so north-facing panels collect the most direct sunlight across the day. That logic is sound, and a north-facing roof is a good place for panels.
But here’s something most installers don’t mention: for many households, north-facing panels don’t always match when you actually use electricity.
If your household uses most of its power in the morning, getting kids ready for school, making breakfast, running the washing machine early, and again in the late afternoon and evening for dinner, TV, and the dishwasher, a north-facing setup means you produce peak power at midday when no one is home.
That extra power goes back to the grid at whatever your feed-in tariff is, which is usually low right now.
At PSC Energy, we call this the 2/3 rule:
- One-third of your panels face east to capture morning sunlight.
- Two-thirds go on the west-facing roof to capture afternoon sunlight.
This layout matches your solar production to your actual consumption. Because most households use more electricity in the afternoon than in the morning, the heavier weighting toward the west makes practical sense. The system is working hardest when you need it most.
This doesn’t mean you should ignore north-facing roof space. If you have it, use it because rooftop space is valuable, and most homes benefit from panels on every available surface.
But if you have to choose between directions or have limited space, matching your panel placement to your usage pattern usually gives you a better return than just aiming for maximum midday output.
East and west panel placement can sometimes work better than a north-facing setup, depending on your energy use and timing. Not every installer will mention this.
If you’re interested in learning a bit more about which way to point your solar panels, you might want to check out the following article titled, Which Way Should Solar Panels Face in Australia?
How to Calculate Your System Size
Here’s how to work out the size of the solar system you need. You need two numbers: your average daily electricity usage in kWh, and the average peak sun hours for your location.
What are peak sun hours?
Peak sun hours are the times of day when the sun is high in the sky and sunlight is strong enough, at least 1,000 watts per square metre, for your solar panels to work at full capacity. Outside these hours, panels still make electricity, just at a lower rate.
For example, they might only produce 500 watts per square metre at 8am or 5pm. That’s why peak sun hours give us the most reliable average.
In Sydney, the average is 3.9 peak sun hours per day.
This doesn’t mean the sun only shines for 3.9 hours. It means that, on average, you get the equivalent of 3.9 hours of full-strength sunlight each day. In summer, you’ll get more peak hours; in winter, fewer.
The Formula
Daily kWh usage divided by peak sun hours equals system size in kW.
Here’s a worked example.
Say your annual electricity bill shows you used 10,000kWh over the past year. Divide that by 365 days, and you get an average of 27.4kWh per day.
Now divide your daily usage by Sydney’s peak sun hours:
27.4kWh divided by 3.9 equals 7.03kW.
You’d need a solar system that produces at least 7.03kW to cover your current daily usage. In practice, most installers suggest rounding up to 8kW or 10kW to allow for system losses, some shading, inverter efficiency, and future growth.
This formula gives you a solid starting point. It doesn’t factor in seasonal changes, roof angle, shading from trees or nearby buildings, or which way your panels face.
Still, it gives you a number you can use when getting quotes. If an installer suggests a much smaller system than this, ask them why. If they can’t explain, take note.
If you’re interested in learning a bit more about oversizing, you might want to check out the following article titled, Oversizing Your Solar Panel System: How to Maximise Your Panels for Bigger Returns.
Future-Proofing Your Solar Energy System
The formula above tells you what you need right now. What you’ll need in five years is a different question.
Several common changes can significantly increase your electricity usage:
Installing air conditioning in a home without it will significantly increase your usage, especially in the summer.
Adding a granny flat or second dwelling creates a second household’s worth of consumption on the same meter.
Installing a swimming pool adds a significant power draw through the pool pump, typically running several hours a day through the warmer months.
Converting from gas to electric for your stove, hot water, or heating shifts that energy demand onto your electricity supply. Australians are making this switch in increasing numbers as gas prices rise.
Working from home on a permanent or semi-permanent basis adds daytime usage that your system might not be sized to handle if it was designed around the assumption that the house is empty during the day.
Buying an electric vehicle is one of the biggest ways you can change your electricity demand. Charging an EV at home adds roughly 10 to 20kWh per day, depending on how far you drive. That’s a meaningful addition to your baseline.
Installing a solar battery changes the whole equation by letting you store excess daytime generation for evening use rather than exporting it to the grid at a low rate. A battery makes a well-sized system significantly more efficient.
If any of these changes are in your near future, include them in your system size now instead of expanding later. Adding panels later is possible, but it’s more expensive and disruptive than getting the size right from the start.
If you think you might want to expand later, ask your installer about microinverter systems. Unlike string inverters, where all panels are connected in a series, microinverters mounts a small inverter to each panel. This lets panels work independently, so shading or a problem with one panel doesn’t affect the others. Adding panels later is also much easier and less costly. Microinverter systems usually cost more upfront, but they’re a good choice if you plan to grow your system.
If you’d like to learn a bit more about what solar batteries are on the market, you might want to check out the following article titled, 6 Best Solar Batteries on the Market.
Wrapping Up: Watt’s the Right Size for You?
The right solar system size is the one that matches your household’s actual energy use, not a number a salesperson landed on before they knew anything about you.
Start by checking your electricity bill and working out your daily usage. Divide that by 3.9 peak sun hours for Sydney to get a baseline. Then consider your future plans, your roof’s direction, and whether a microinverter system fits your needs.
If you’d like help working out the numbers for your home, contact the PSC Energy team. We’ll ask the right questions, show you how we calculate everything, and recommend a system that fits your needs. It’s what we do.
If you’re interested in learning a bit more about solar panel efficiencies, you might want to check out the following article titled, How Efficient Are Solar Panels? Shade, Heat, and Seasonal Considerations in NSW, Australia.
FAQ: Sizing Your Solar Energy System
How do I find my annual kWh usage?
Check your electricity bills. Most bills show your usage in kWh for the billing period. If you have access to your retailer’s online portal, you can usually download a full year of usage data in a single download. Add up 12 months of bills and divide by 365 to get your daily average.
Is a bigger solar system always better?
No. A bigger system costs more at the start, and if you don’t use much electricity, the extra panels might not pay for themselves quickly. The goal is to match the system to your current and future needs. If your usage is low and unlikely to grow, a smaller system can still give you a good return. Bigger only makes sense if your usage justifies it.
What if I don’t have a north-facing roof?
East and west-facing roofs can work very well, especially if you use most electricity in the morning and afternoon. PSC Energy’s 2/3 rule is made for this situation. A good installer will look at both your roof orientation and your usage pattern before making a recommendation. Don’t assume your roof is a problem until an expert has checked it.
Will I still get electricity bills after installing solar?
Yes, in most cases. Solar will cut your electricity bills a lot, but it won’t get rid of them unless you also have a battery big enough to cover your evening use and your system is sized for all your daily needs. Most homes with solar see much lower bills, not zero bills. A battery can almost get you to zero.
What is the difference between a string inverter and a microinverter?
A string inverter connects all your panels in a series. If one panel underperforms due to shade or debris, it reduces the output of the whole string. Microinverters are mounted beneath individual panels, so each panel operates independently. String inverter systems are less expensive upfront and are a solid choice for roofs with minimal shading and a single orientation. Microinverter systems cost more initially but perform better on complex roofs, are easier to expand, and give you panel-level monitoring so you can see exactly how each panel is performing.
How often should I review my solar system size?
You should review your solar system size whenever your lifestyle changes in a big way. Buying an EV, having more people in the house, working from home, adding a pool, or switching from gas to electric are all good reasons to check if your system still suits you.
