Commercial solar system sizing is pivotal. In fact, the most important aspect of commercial solar design is sizing. The wrong solar power system size means that you are missing out on precious savings one way or another. An under-sized system is obviously not working as well as it could be and an over-sized system will deliver an excess of solar power to the electricity grid, meaning you are not taking maximum advantage of the power availability and you’re probably not getting much (if anything) for the excess power.
How To Size Your Solar Power System (basic)
The most basic way to work out your commercial solar power system sizing is to use the same method as for residential solar power systems, ie:
- Determine your daily kWh consumption
- Narrow this down to daylight-hours consumption only (not including the night)
- Divide this number by 4.2 sun-hours
- This is your system size give or take
So for a business that uses 127kWh/day – maybe 80% is during daylight hours, which makes 101.6kWh, then divide this by 4.2 >> 101.6/4.2 = 24kW solar power system size.
Now this is fine to get a basic idea of how to size a commercial solar power system, but for the astute business owner / investor, it may not be accurate enough…
Why Should You Look At Interval Data And/Or Log Your Electricity Use
Interval data is precious when it comes to accurately sizing a commercial solar power system. If you are setup as a large customer with your electricity retailer and are charged on an unbundled bill, then you can request the last 12 months worth of interval data from your retailer so see exactly when you are using power and how much is being used.
This helps massively. The easiest way to work out what the best size of your system will be once you have the interval data is to see how much power you are using in the middle hours of the day (between 11am and 1pm) and add 20%. So if your power usage profile (in kW) reaches 70kW at midday then you would need an 84kW solar power system.
Interval data is the best way to determine your commercial solar power system size, although not the most accurate. Usually you can obtain 15minute interval data which is sufficient in most cases. If you need more accuracy then you may need to hire an electrical professional to log your data in closer intervals – this can be done within about 15 second intervals, which is a little extreme for the purposes of solar power system sizing.