Solar power system sizes? Which is best for your home?
With a grid-connected system, you are free to install any solar power system size. To figure out which system size you might like to install, there are three key factors you might want to consider first. Do you want a solar power system that will:
- Eliminate or reduce your power bill;
- A system that has the maximum amount of solar panels that will fit on your roof or
- Fits your budget
To give you an idea of the solar power system sizes range, the smallest system size a solar power installation company will normally offer is a 1.5-kW system.
A 5kW to 6kW system would produce enough electricity to match the amount of electricity that the average New Zealand home uses in a year (7,000kWh/year).
Matching a system size to your power demands doesn’t mean that you will eliminate your power bill, particularly if you end up exporting a lot of power to the grid. Even though you do get paid for power that you export, you just don’t get as much as what they charge you for power.
If your aim is to eliminate your electricity bill you might want to think of ways that you can use as much of the solar power when it is created i.e. during the middle of the day. This is known as solar power self-consumption, click here to read more about it.
A popular system size in New Zealand for home owners is a 3kW system. In Auckland it will generate around 3740kWh/year. For the average New Zealand household you won’t be eliminating your power bill with a 3kW system. But with a slightly smaller size system it is easier to ensure that the majority of the power from the system is directly used by your household and less is exported to the grid.
What does it mean to have a 1.5-kW system?
Do not get too caught up in the title of your system size. What’s more important is to find out how much power the system will provide for you in a year.
Put simply, having a 1.5-kW system means that at any given time on a clear, sunny day, the system will produce up to 1.5 kilowatts.
This graph is provided only to help reinforce the point above; the data is not precise.
A 1.5-kW system in Auckland will produce an estimated 2,000 kWh annually. For some people this will half their electricity bill, for others it will reduce it by a quarter. You can find out how many kWh’s you use in a year from looking at past power bills.
Scalable system sizes
It is possible to scale up the system size after a year or two if you would like to start off with a smaller system. There are 3 main considerations for this option.
- You will need to install a larger inverter size initially. For example you could have a 3kW system with a 5kW inverter. After a while you could add extra panels to build up to a 5kW system.
Not all larger inverters are compatible with smaller system sizes, so you will need to ask the solar power company which larger inverters will be compatible with a smaller system size. - Secondly, you will need to make sure you can get the same type and size of panels in a few years time. If you initially go for the standard 190W panels you will likely be able to get these panels again. This is important, because if you get panels that are a different sizes then you will probably experience some power loss.
- You will need to be sure you have enough roof space to add extra solar panels to the system later down the track.
Scaling up with a micro-inverter system
With a micro-inverter system, it is modular, so you can add one panel at a time if you wanted to. You would just need to consider the cost of getting an installer out to your house every time you install another panel. For additional panels you do not need to worry about matching the panel size to the previous size panel you already have on your roof.
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