Creating an easy-to-use Battery and Inverter sizing calculator

[Battery Bob]

Good day! I am trying to build an easy-to-use online battery and inverter sizing calculator for people in South Africa, or anywhere in the world to use. With load-shedding in South Africa, many people want some solution to the power outages (rolling blackouts) and people get all sorts of advice from different people and end up being confused about what solution will suit their needs the best.

The idea is to first - have the people select the appliances that they plan to use (from a dropdown menu) Each appliance has an estimated prefilled wattage power consumption.

Then a global variable for the number of hours that the person wants backup power (which gets multiplied by the W of the appliances)

The challenge comes in when there is coffee being made (how many cups? additional variable?) a hairdryer for example is around 1000W, but only for 10 minutes in an hour and seldom more than once a day for the average household. Even a water pressure pump, will only start a couple of times per hour, but I will need to add a value for x number of minutes per hour of runtime.

I thought it would be a good idea to get some advice from the community as we all have different opinions and from that, I would like to build the best, simplified, easy-to-use but fairly accurate free-to-use online calculator. I know there already exist calculators, but they just don't feel that user-friendly to me.

I am looking forward to your input regarding the different appliances you would suggest and also how you would approach the problem. In South Africa, power outages are normally 2 hours or 4 hours at a time.

 

[xjaw4]

http://www.batterysizingcalculator.com/ check out what exists already

 

[Battery Bob]

I have seen many of these, my aim is to build one that is a little bit less cluttered and easy to navigate.

 

[Battery Bob]

The idea so far is to list the following appliances:
LED Light, Fridge, Freezer, TV, Decoder, Sound System, Wi-Fi, Laptop, Desktop, Water Pump, Microwave, Air Fryer, Kettle, Hair Dryer, Heater, Aircon, Geyser, and also a custom appliance.

 

[Shimmy]

I would suggest a place to put in monthly energy consumption to kind of validate numbers or widen a recommended range. If you know average consumption for your target audience (and profiles if applicable) then it helps even more.

Specific to SA, is it a specific time of day that is a problem, or really overall?

 

[pollenface]

my advice to anyone is to double your inverter size so it only runs at 50% load, less heat, less fan noise. Also no one can help themself not to try to run as much as they can from their inverter as time goes on so there will always be room to grow

Look at Will's videos, he said get the BIG one cos you'll always wanna run more stuff. Otherwise you'll just waste money on a small one and replace it with something bigger later on.

 

[Battery Bob]

I would suggest a place to put in monthly energy consumption to kind of validate numbers or widen a recommended range. If you know average consumption for your target audience (and profiles if applicable) then it helps even more.

Specific to SA, is it a specific time of day that is a problem, or really overall?

I agree with your suggestion and it is a valid solution if you are looking at the total house consumption, but many people in SA can only afford a very small system to power the most basic things like a TV, Wi-Fi, and a couple of LED lights. So I wish to build on this conservative tool to give someone the opportunity to educate themselves on a simple and efficient way. Thanks for your input! I really appreciate it!

This problem varies really. It depends on which issues there are in the power production infrastructure.

 

[Battery Bob]

my advice to anyone is to double your inverter size so it only runs at 50% load, less heat, less fan noise. Also no one can help themself not to try to run as much as they can from their inverter as time goes on so there will always be room to grow

Look at Will's videos, he said get the BIG one cos you'll always wanna run more stuff. Otherwise you'll just waste money on a small one and replace it with something bigger later on.

I fully agree with your advice. We have been in the battery and solar industry for quite a while and more often than not, people want to expand their AC capacity in the future. Buy once and save time and effort in the future.

 

[Shimmy]

I agree with your suggestion and it is a valid solution if you are looking at the total house consumption, but many people in SA can only afford a very small system to power the most basic things like a TV, Wi-Fi, and a couple of LED lights. So I wish to build on this conservative tool to give someone the opportunity to educate themselves on a simple and efficient way. Thanks for your input! I really appreciate it!

I guess where I think it adds value for you is saying that this system is likely able to back up x% of your needs.

Or, you could treat it like a menu solution. Match consumption, perceived needs, and budget to not only help people size their system but to get a handle on what incremental value they get with each incremental spend.

My thinking relative to the US is that sometimes someone can spend less and get greater value for both themselves and their community. Not sure how well that translates for your situation.

 

[SeaGal]

The challenge comes in when there is coffee being made (how many cups? additional variable?) a hairdryer for example is around 1000W, but only for 10 minutes in an hour and seldom more than once a day for the average household.

LOL.. guess you don't have daughters then

The idea so far is to list the following appliances:
LED Light, Fridge, Freezer, TV, Decoder, Sound System, Wi-Fi, Laptop, Desktop, Water Pump, Microwave, Air Fryer, Kettle, Hair Dryer, Heater, Aircon, Geyser, and also a custom appliance.

An Oven, Washing Machine and Tumble Dryer would be major power consumers for us, but not on your list - assume you use those in SA too?

 

[n2aws]

The idea so far is to list the following appliances:
LED Light, Fridge, Freezer, TV, Decoder, Sound System, Wi-Fi, Laptop, Desktop, Water Pump, Microwave, Air Fryer, Kettle, Hair Dryer, Heater, Aircon, Geyser, and also a custom appliance.

Maybe Add an optional input field next to each of these. if left blank, use some standard times. if populated, use their numbers in the calculation.

The field would be "runtime". and in the case of a TV, could be "hours a day". or hair dryer could be "minutes a day"
Or, for the sake of consistency, just make them all "minutes per day"

In the background, make some assumptions that are logical. ie, 20m hair dryer. 2 hours for a TV, etc. but this would allow them to change hair dryer to "40" if there are 2 people in the house that use it daily.. etc etc.

 

[Battery Bob]

LOL.. guess you don't have daughters then


An Oven, Washing Machine and Tumble Dryer would be major power consumers for us, but not on your list - assume you use those in SA too?

At this stage no daughters yet. I can add those yes (your 3 suggestions ). They are however quite difficult items to factor in for battery sizing, but would make the calculation much more conservative if you go with their rated power as the oven, washing machine and the tumble dryer normally use less than their rated. Thanks for your input!

 

[Battery Bob]

I guess where I think it adds value for you is saying that this system is likely able to back up x% of your needs.

Or, you could treat it like a menu solution. Match consumption, perceived needs, and budget to not only help people size their system but to get a handle on what incremental value they get with each incremental spend.

My thinking relative to the US is that sometimes someone can spend less and get greater value for both themselves and their community. Not sure how well that translates for your situation.

I like the part for the value they add for the incremental amount they spend extra. The price of products in general are so all over the show as well as quality, but somewhere I would like to give people an idea of this will be your battery size and this will be your inveter size. Without overcomplicating it for myself as well as the user. Thanks for your input!

 

[SeaGal]

Agree - there is little data regarding duty cycle for many of these heating devices - guess because it varies between different users and equipment.

From my experience (if this is of any help);
Oven on 75%; off 25% (ish)
Washing machine - on full for about 30 mins, then very low (100W or so)
Tumble Dryer - on virtually all time, till very end.
Air Fryer - on 50%, off 50%.

 

[Shimmy]

Agree - there is little data regarding duty cycle for many of these heating devices - guess because it varies between different users and equipment.

From my experience (if this is of any help);
Oven on 75%; off 25% (ish)
Washing machine - on full for about 30 mins, then very low (100W or so)
Tumble Dryer - on virtually all time, till very end.
Air Fryer - on 50%, off 50%.

I and some other members run IoTaWatt and have good appliance data in terms of peak energy, duty cycle, and energy consumption average if there are any specific loads that details would help on.

For refrigerators, ice makers and dispensers, and dual compressor designs can make loads vary from 1-4kWh/day.

My dryer and oven generally pulse full power to the heating element for a few seconds or minutes to modulate temperature, so it can easily peak at 5kW while running for an hour, but total energy consumption is about 1kWh per load.

 

[Battery Bob]

I and some other members run IoTaWatt and have good appliance data in terms of peak energy, duty cycle, and energy consumption average if there are any specific loads that details would help on.

For refrigerators, ice makers and dispensers, and dual compressor designs can make loads vary from 1-4kWh/day.

My dryer and oven generally pulse full power to the heating element for a few seconds or minutes to modulate temperature, so it can easily peak at 5kW while running for an hour, but total energy consumption is about 1kWh per load.

Thanks for everyone's input. It is truly appreciated. I will share my progress as soon as I can show something that works and then I can expand it from there!

 

[CoolWill]

Make it so that when the user selects South Africa, the app sends them to an airline webpage so they can buy a ticket out.

 

[Battery Bob]

Agree - there is little data regarding duty cycle for many of these heating devices - guess because it varies between different users and equipment.

From my experience (if this is of any help);
Oven on 75%; off 25% (ish)
Washing machine - on full for about 30 mins, then very low (100W or so)
Tumble Dryer - on virtually all time, till very end.
Air Fryer - on 50%, off 50%.

I have yet to build in your advice, but I would for now like to share my basic calculator so far. Please note I am not a programmer and that I made use of Chat GPT4 to help me build this calculator. It is exciting what can be achieved with the use of AI without any experience in HTML coding.

So I have made some basic progress with the battery and inverter sizing calculator. It is still far from complete and far from perfect (I don't think it can ever really be perfect due to the listed and discussed challenges), but that is not the idea here, it is to give people in SA an idea of the size battery and inverter that they might need. I am sharing it so long so I can get some assistance on how to improve it for ease of use and to give a fairly accurate answer to the user. I will build in all the advice as far as possible as time goes on! It is quite an exciting project for me

A fantastic Sunday for everyone and thanks for all your advice so far!

 

[CoolWill]

I like that it has no bounds and will take whatever input and give an output. For example, my appliance rated for 5531.7 watts, 12 volt battery, DoD of 21%, operating for 117 hours on a 9% efficient inverter requires a 2853655 Ah battery.

 

[Battery Bob]

I like that it has no bounds and will take whatever input and give an output. For example, my appliance rated for 5531.7 watts, 12 volt battery, DoD of 21%, operating for 117 hours on a 9% efficient inverter requires a 2853655 Ah battery.

Thanks for your feedback and taking it for a spin. I will as promised make more and more edits to the calculator to improve its accuracy whilst still keeping it as simple as possible to use.


One thing that I wanted to change that bothers me about other calculators is that I did not want to have a calculate button. A small thing, but it is one less place to click so makes it faster for its user to get to the answer they want

I think that I must maybe add optional 12.8V 25.6V 38.4V and 51.2V to accommodate for 4s 8s 12s and 16s LiFePO4 batteries. My only thing again is, I want to keep it as simple as possible for the user, or they must type in their nominal battery voltage manually. Please share your thoughts on this!