I've got these appliances, what kind of solar system do I need?

I've got these appliances

This question comes up all the time in DIY forums.

There are various ways to go about answering it. In previous blogs I've gone over some of these, like staring with the area that you have available, and how to figure out if that is enough for a particular appliance.

Today, we're going to start with a list of what we want to power and go from there. A couple of people have said they watched videos and stuff, but somehow they just don't get it, so let's see if we can clarify.

Here was the question from a forum:

"Been a part of the group for awhile and still feel like an idiot because I really don’t understand

Looking for a solar set up for our off grid cabin. ….. here’s what we need powered 

A couple lights, starlink, tv, couple charging cords, space heater, & possibly a small AC and mini fridge."

My response to this poster was to ask what in particular she didn't get in order to narrow it down a little bit, and that so long as you are organized, can keep track of things, and can do some googling, its all there for her. There is some basic math involved, but so long as you can handle addition, subtraction, multiplication, and division, that's all you need.

For each thing, there are two major questions that have to be answered: 1) how much power does it draw, and 2) how long will it be on for.

A couple of lights

Well the next question is "What kind of lights?" Are they LEDs or incandescents?  This will make a big difference in their power draw. Remember that bit about Googling? Well if we ask "What is the typical power draw for LED lights?" here is the answer that the google machine gives us:

"A typical LED light bulb, designed to replace a 60-watt incandescent bulb, draws around 10 watts of power. 

Here's a more detailed breakdown:

• LED vs. Incandescent:
  LED bulbs are significantly more energy-efficient than traditional incandescent bulbs. 

• Wattage Range:
  LED bulbs typically range from 2 to 18 watts, while incandescent bulbs range from 25 to 100 watts. 

• Brightness:
  LEDs can achieve the same brightness as a 60-watt incandescent bulb with a much lower wattage. "

So there it is, in the typical use case, around either 10w or 60w. She also said a couple. How many? It's important when calculating your energy consumption. Let's assume 4. So the total will be either 40w or 240w. Big difference there.

And how many hours will they be on for? 

Will they be on 24/7 or just during the evening hours? 

If 24/7 you've got 40w * 24hours = 960 watthours (wh) for LEDs or 240w * 24h = 5,760wh for incandescents. Again big difference.   

If only during the evening hours lets say from 5pm to 8am, its the same calculation but for only 15 hours, so either 600wh for LEDs or 3,600 wh for incandescents.

Starlink

 We have to repeat the above calculation for each thing we want to power. So you have to figure how much power does it draw and how long will it be on for (ignoring for the moment the parasitic draw when it is plugged in but not explicitly On). And again there will be a range depending on the particulars of your actual device.

Google:

"The standard Starlink router, including the antenna and power cables, consumes between 50W and 75W when connected to low Earth orbit (LEO satellites) and about 20W when connected to the internet without network usage."

So lets assume 12 hours of usage so we've got 20*12 = 240 wh and between 50*12 = 600wh and 75*12 = 900wh depending on which starlink you have.

TV

Again there is going to be a wide range depending on the type of TV.

Google:

"Modern TVs typically draw between 50 and 200 watts of electricity, but this can vary significantly based on the model, size, and technology used. "

And how long will the TV be on? Best case and worst case or average? Google: "In 2023, the average American watched about three hours of TV per day, says Statista. This includes watching TV on TV sets, computers, and portable devices."

So worst case 200w * 24h = 4,800 wh vs. best average case 50w * 3h = 150wh.

Couple of charging cords

I think you get the idea by now, yes? What will the cords power and for how long, and how many of them are there? Best and worst case scenarios. Ask Google. You can easily see there will be quite a spread depending if they are powering laptops or phones, for instance.

4 laptops 24/7 = 4*70w*24 = 6,720 wh. vs. 4 phones 8 hours a day = 4*5w*8h = 160wh.

Space heater 

These next three are the real power hogs and will have the greatest variability in their power usage depending on what type and how large they are. Generally, a space heater will use between 1,500 and 1,800 watts. The real question is for how long? 12 hours? 24? 1500w*12=18kwh and 1,800*24=43.2kwh.

A small AC

A typical small window or portable air conditioning unit draws between 500 and 1,500 watts of power, depending on its size and cooling capacity. For 12 or 24 hours that gives us 500w*12h= 6,000wh or 1500*24=36kwh

 A mini fridge

A typical mini fridge draws between 50 and 100 watts, but this can vary based on size, efficiency, and features like a freezer. So that gives us a range of 50w*24h=1200wh and 100*24h=2400wh.

Putting it all together

Now we just add it all up on the low end and high end, and that gives you the upper and lower bounds on the system design and depending on your particular system.

Load Low End Upper end

Lights 600wh 5,760wh

Starlink 240 wh 900wh

TV 150wh 4,800 wh

Charge cords 160wh 6,720 wh

Space Heater 18kwh 43.2kwh

Small AC 6,000wh 36kwh

Mini-fridge 1200wh 2400wh

Totals: 26,350wh 99,000wh

So there you have it. That is quite a spread based on the assumption of which appliances and how long they are used. Obviously, we wouldn't be using the space heater and the AC on the same day, which this analysis doesn't account for, and the space heater is by far the largest power hog, so it would make sense to look into alternatives for heating like natural gas.