Sizing
What size of inverter do I need?
When sizing your system, add the total power consumption for all devices you'd like to keep running when power outage occurs. This total power consumption should be 50% of the inverter size you pick. When running the inverters at half the capacity, it puts less stress on the output and therefore giving you longer life time of the product. Additionally, this will give you extra room in case you need to add additional equipments in the future. Here is an example (Wattage used below is for reference only):
Tankless water heater: 125W
Gas room heaters: 150W
Router @ 10W for 24hrs: 240W
Refrigerator: 200W, this is an inductive load, so starting power might be 1200W.
LED light bulb (4 bulbs): 8W * 4 = 32W
This above totals to 747W. 747 * 2 = 1494W. In this case, the SigmaPro3024 would be the ideal system by allowing load to be equal or less than 50% of inverter's rated capacity. Now, depending on how long you wish to run these devices will determine how you will build your battery bank. Download our worksheet here to plug in some numbers and try different configurations.
What battery bank size do I need?
When deciding how to properly build battery banks, it is critical to important to make calculations on which devices required to be running, for how many hours per day, and for how many days. Take the example from above:
1 hr of hot water usage: 125W * 1 = 125W
2 hrs of room heater: 150W * 2 = 300W
Router (per day) = 240W
2 hrs of Refrigerator: 200W * 2 = 400W
4 hrs of Lighting @ 8W/LED bulb * 4 bulbs: 8 * 4 * 4 = 128W
The above totals to 1193W or 1.2KW per day. Assuming inverter efficiency is 85%, and assuming we are going to use 24VDC battery bank.
1200 Watt hours / 85% / 24 Volts = 58.8 Ah/day, for calculation, we will use 60 Ah/day.
If we want to prepare for 3 days of power outage and that our battery discharge limit (DoD) is 50%:
60 (Ah/day) * 3 (days) / 50% (DoD) = 360Ah
This is the total battery amp hour needed for the above scenario. If the battery is 200Ah, there will need to be 2 sets of batteries connected in parallel and we will have 400Ah.
The SigmaPro 3024 is a 24VDC system, which means there needs to be two (2) 12VDC batteries connected in series for each set and we need 2 sets. This means the battery bank should be four(4) 200Ah 12VDC Sealed Lead Acid batteries, 2 wired in series and 2 wired in paraelle to achieve 400Ah at 24VDC. This will allow the above equipments to be running for 3 days on battery power only.
Batteries wired in series (Ah for reference only)
How many solar panels do I need?
Solar panels will enable the Sigma inverter to operate to its fullest potentials via SBU mode. When solar energy is sufficient, inverter will convert and direct solar energy to power loads, any excess power will be used to charge the battery. Therefore, it's important to know how many panels you need in order to operate the most efficient way possible.
Again, we take our previous example of 60 Ah/day, assuming battery efficiency is 80%, and if there is 5 hours of peak sun power per day.
60Ah / 0.8 / 5 = 15 ah/day
Our SP200W-18V solar panels are rated for 200W per panel with 11.2 Imp (max current rating). We take 15Ah/11.2 = 1.34 solar panels, this is the number of panels needed to keep loads running. We round up to 2, which means 2 sets of solar panels wired in parallel. When sun power is not 5 hours, we now have the extra panel space to compensate.
We hope the above will give you some basic information to start sizing your solar system. This may seem cumbersome or overwhelming, no worries. Reach out to our Sales Team today and our team member will be able to help you size out a perfect system. You can also download our worksheet here to try different options.