in this video you're going to discover exactly how many batteries and solar panels are needed to power your loads effectively I've laid out a comprehensive guide to sizing your offgrid solar system from analyzing the different loads selecting the battery voltage determining days of autonomy calculating battery size finding your amount of sun hours and lastly calculating how many solar panels you need I'll be presenting this video in an over-the-shoulder format making it easy for you to follow along with the calculations Plus for those who prefer a more direct approach there's a link in the description to a calculator where you can input your own data and it will do the heavy lifting for you let's dive in and get your offgrid s system perfectly sized step one analyzing the loads the first and crucial step in sizing your offgrid solar system is to listen list all your appliances and determine their usage duration let's start with a system one of my clients has requested he has several lead lights totaling 20 watts which is being used for about 8 hours on a typical day these lights are DC powered straight from the battery so no need for an inverter now let's move on to AC devices the fridge is 100 wats with a 30% duty cycle this means the compressor is active for about 8 hours a day remember if your fridge is in a warmer location the usage might increase the laptop charger indicates a power draw of 35 wats and is used for 4 hours daily additionally a 50 W TV needs to be powered for 1 hour a day a quick tip for appliances with short run times like a cattle convert their usage into hours for example 5 minutes divided by 60 Minutes becomes 83 hours regarding the inverter he uses a 1,000 watt model to handle the fridge search Power it's important to note that a 1,000 watt inverter has a standby consumption of around 20 watts larger inverters like a 3,000 wat model uses about 30 watts and hybrid inverters can consume up to 50 Watts this standby power also needs to be factored into the total load calculation after tying up these numbers we arrive at a total consumption of 1,630 w hours we will use this value later in our calculation step two selecting battery voltage choosing the right battery voltage is a critical decision in setting up your upgrade solar system as I've discussed in previous videos it's advisable to limit the current in your DIY upgrade system to 100 amps let's quickly recap why opting for a higher battery voltage is beneficial it reduces wiring cost it increases overall system efficiency it decreases the current requirements for the charge controller all these factors contribute to significant Savings in your installation to maintain the current below 100 amps here are my recommendations for Inver sizes based on the battery voltage for a 12vt battery system use a 1,000 W inverter or lower for a 24v volt battery system choose an inverter ranging from 1,000 to 2,000 Watts for a 48 volt battery system you can go up to a 5,000 W inverter if you need more power consider adding multiple inverters in parallel for example if you're using a 1,000 wat inverter with a 12 12 Vol battery the calculation would be 1,000 wat divided by 12 Vols resulting in 83 amps to ensure safety we apply a factor of 1.25 or 125% which brings us up to4 amps therefore a 100 amp fuse would be appropriate for this inverter however let's not get Sidetrack and focus back on the main topic step three days of autonomy this step involves deciding how many days you want your system to run solely on battery power assuming no solar input this is known as days of autonomy I recommend planning for three days to ensure a reliable power supply even during consecutive days without sunlight this duration is a balanced choice for most setups however if you're connected to the grid one day of autonomy might be sufficient step four calculating battery size now let's dive into some calculations for both lead acid and lithium batteries there are two key factors to consider in this calculation for L acid batteries remember that you can only use about 50% of their capacity and they have an energy conversion efficiency of around 80% that means that for every 100 W hour you put into the battery you would get about 80 W hours of usable power referring back to our load analysis from step one where we calculated a total daily usage of 1,630 wat hours the calculation for 3 Days of autonomy would be 1,630 wat hours which is a daily usage times three which is a days of autonomy times two which is 50% usable capacity of the battery time 1.25 which equals 80% % efficiency equals 12,225 W hours to determine the required battery capacity and amp hours divide this number by the battery voltage 12,225 W hours divided by 12 volts equals 1,8 amp hours for lithium batteries the scenario is more favorable you can use up to 80% of a lithium batteries capacity and they boast a higher energy conversion efficiency of 99% applying the same load analysis we get 1,630 W hours which is a daily usage time 3 equals the days of autonomy time 1.25 equals 80% usage time 1.01 equal 99% efficiency and we become 6,173 W hours dividing this by the battery voltage gives us 6,173 W Hours ided by 12 volt equals 514 amp hours this comparison clearly shows that lithium batteries require a much smaller capacity than Le acid batteries for the same energy needs thanks to their higher efficiency and greater usable capacity step five finding out your sun hours now it's crucial to determine the average Sun hours your location receives especially during winter as this will impact your solar panel requirements for this we use a handy tool called PV Watts available at the link in the description let's walk through the process together first enter your location on the website I will use ENT taxes as an example since many of my subscribers are based there once you've confirmed the location on the map proceed to the system info section you don't need to modify any Fields here just just head straight to the PV wats results in the results section pay close attention to the left column it displays the average Sun hours for each month for sizing our solar system we focus on the month with the least Sun hours as this represents the most challenging period for solar power generation in the case of Houston the lowest Sun hour month is December averaging about 3.47 hours per day a understanding your location Sun hours during the least Sunny month is key to ensuring your upgrade system can reliably generate enough power year round step six calculating solar panels the final step is to determine the number of solar panels needed to charge your battery Bank within a single day especially during the least Sunny month this calculation ensures your system is equipped to handle the most challenging conditions let's start with lead asset batteries since you can only use 50% of lead asset's battery capacity you only need to recharge the second half for example if your total battery capacity is 12,225 W hours you will need to recharge 6,112 W hours in a day this reduced figure reflects that you're only recharging from 50% to 100% now divide this daily recharge requirement by the average Sun hours using our previous example of Houston in December with 3.47 sun hours the calculation would be 6,112 W hours ided by 3.47 hours equals 1,760 W of solar power therefore you need around 1,760 WTS of solar panels to recharge the lead acid battery in a day for lithium batteries the calculation is slightly different considering you can use 80% of lithium's battery capacity let's say you need to recharge from 10% to 90% using the same total capacity of 6,173 w hours you'll need to recharge 4,938 W hours in a day again divide this by the sun hours 4,938 W hours divided by 3.47 hours equals 1,420 Watts so for a lithium battery you will need about 1,420 WTS of solar panels to ensure a full days recharge during winter remember these calculations are based on the worst case scenario typically the winter months during summer your system will recharge more quickly due to Long Sun hours but it's crucial to size your upgrade system for the most challenging times of the year and that's how you calculate the solal panel requirements for your upgrade soloro power system thanks for watching like this video if you want more information like this are you confused about solar power get my seven free solar diagrams through the pinned comments below
