Solar power looks like it will be the main way that households will produce clean electricity. But how many 100 watt solar panels does it take to run a house?
With the rising cost of fossil-fuels and the need to go green for the sake of our wonderful planet’s environment. Many people are now thinking about turning to solar power for their energy needs.
Over the last few years the cost of installing solar to a house has come down. So financially speaking the technology has become a better prospect. Because more households are taking advantage of solar grants. It is likely in the future the price will come down even further.
But does the 100 watt solar panel have a part to play in the home solar revolution?
How Many 100 Watt Solar Panels Does It Take To Run A House?
“ The number of 100 Watt solar panels it takes to run a house depends on how much electricity is consumed per day. According to The U.S Energy Information Administration the average household uses 2,918 watts per day. That equates to 30 x 100 watt solar panels. As you can see, using 100 watt solar panels to run a house is probably impractical.”
The average 3 bedroomed house would not have enough roof space to accommodate all those panels. Yard space would need to be used to complete such an installation. Using 100w panels may seem attractive because they are much cheaper. But in reality they are dwarf panels and are not up to the job.
Much larger wattage solar panels would be required to completely power the house. But you can use 100 watt solar panels at your home to provide solar power for outbuildings.
How Can I Use 100 Watt Solar Panels To Power Outbuildings At My House?
100 watt panels can be used to provide solar power to outbuildings such as sheds, garages and workshops. This is because these types of buildings usually need fewer watts to power them.
Say you have a shed at the end of the yard at your house. You want to provide electrical lighting and power sockets to it. You have had a quote to provide electrical cables to it but it is too expensive. Or you want to start to become more energy self-sufficient and solar power seems a good viable solution.
100 watt panels are a great way to achieve this because they are smaller so taking up less roof space.
What Components Would Be Required To Install 100 Watt Solar Panels To An Outbuilding Such As A Shed At My House?
The first thing you would need to think about is not the amount of solar required. It is what size AC inverter you will need?. This will be determined by the type of appliances you want to power from the shed. You might want to power:
- Power Tools
- A Radio
Because we are talking about powering a shed the appliances you will be using will not be powered 24/7. It will be mainly at the weekend and sometimes at night. So you will need an inverter that can handle the lights, a power tool such as a drill and the radio. I can’t see you using more than those 3 at the same time.
Let’s look at the typical wattages of those AC appliances.
- A 25 watt CFL light bulb (equivalent to a 100w incandescent bulb)
- A 800 watt drill
- A 5 watt digital radio
That is 830 watts of continuous power required and taking the drills surge into consideration at start up. It would be best to go for a 2000w inverter because you might also want to use higher wattage power tools.
It is unlikely that you would use the drill for more than 30 minutes per session. But you may have the radio switched on for 8 hours and the lights for 3 in the evening.
This might equal a total power consumption of 915 watts over the day. Assuming it is a 12V system we now need to convert the watt usage to amps. This will then allow us to size the battery for the system.
To do this we need to divide the number of watts the appliance consumes per hour by the volts (12). Then multiply by the number of hours the appliance is used to to find the total amp consumption. The drill isn’t being used for a whole hour. So for 30 minutes use its total amp consumption needs to be halved.
|Appliance||Watts||Amps Consumed Per Hour||Hours used||Total Amps consumed|
|Drill||800 watts||66 amps||30 Minutes||33|
|Lights||25 watts||2.03 amps||3Hrs||6.09|
|Radio||5 watts||0.42 amps||8Hrs||3.36|
|Total||830 watts||68.45 Amps||42.45|
The table shows quite clearly that a 100Ah LiFePO4 battery is required to power this particular shed setup. If you were to use lead-acid it might be prudent to use a higher amp hour battery.
Because it is better to overestimate the battery amp consumption due to inefficiencies in the system.
There is also the 50% rule and the inverters power consumption to take into consideration. When considering using lead-acid.
The 100 Watt Solar Panels
Now we know the size of the battery that is required to power the inverter. It is now time to look at how many 100 watt solar panels will be required to keep the battery charged. You might have realised by now that it will take fewer panels to power a shed than for your house.
To work this out we base the calculation on battery amp hours.
Take the battery amp hours (Ah) and multiply by volts (V) equals watt hours (Wh). Then watt hours (Wh) divided by sun hours (H) equals solar panel wattage. In this case to cover all sunlight scenarios we will use 5 sun hours per day and a 12V 100Ah LiFePO4 battery.
100Ah x 12V = 1200Wh
1200Wh divided by 5H = 240 Watts
This means that 240 watts of solar power are required to keep the battery charged. I would normally round that up to 300 watts. But in this case because you may not be using the shed every day, possibly mainly at the weekend. 2 x 100 watt solar panels should be ok.
If you are using the shed frequently it would be better to install 3 x 100w panels to make sure the battery remains properly charged.
The Solar Charge Controller
The solar charge controller is a very important part of the system. This is because it will make sure your battery isn’t damaged by overcharging.
If you use 2 x 100 watt solar panels for your system you will need a 20A solar charge controller. 3 x 100 watt solar panels will require a 30A solar charge controller. It is better to use an MPPT controller as this is more efficient than it’s PWM counterpart.
How Easy Is It To Install The 100 Watt Solar Panels To A Shed At My House?
If you are reasonably good at DIY you should find it quite easy to fit the 100 watt solar panels to the shed. It would be better if you had a shed roof that is sloped and facing south. This is because the best sunlight is captured between 11am and 4pm from a southerly direction.
It is also important that the panels are not shaded by overhanging trees as this will prevent solar collection. If your shed roof isn’t sloped but facing south you could use a frame to mount them at a 45° angle.
It is always better to have solar panels installed at an angle. Because they collect significantly more sunlight in this position compared to panels laid flat on the roof. If your shed’s roof isn’t sloped or facing south or is overhung by foliage and trees. It would be better to install the panels to a frame on the floor of your yard.
Inverter And Battery
When thinking about where to place the battery and inverter in the shed, water needs to be taken into consideration. If you have them on the floor and there is even a small flood or excessive ingress.
You can kiss goodbye to your investment so you should install in an elevated position. Say a purpose built bench or shelf to make doubly certain you might want to box them in. Because a shed is a confined space if you fit lead-acid batteries use the sealed variety.
Solar Charge Controller
Lot’s of manufacturers say that their solar charge controllers are waterproof. This is true but the terminals are not and though many provide waterproof caps for terminal endings. Because the installation is a shed and may not be 100% waterproof. Think about making doubly sure with waterproof tape.
If your DIY skills are rubbish and you don’t feel you will be able to solar your shed, garage or workshop yourself. You could always pay a qualified tradesperson to do it for you !!!!
My Closing Thoughts
Now you know 100 watt solar panels are not really suitable to run your house. But can be used for other applications like outbuildings at your home. Now you can move on and start thinking about what size solar panels you would actually require.
If you fit into the average household category you will require 2.918 watts of solar power. You then need to add 25% to take environmental conditions into account such as clouds. That means you actually need 3.648 watts (3.65Kw) of solar.
There are many solar panel sizes out there including a jumbo 800 watt. But the size of the panel will depend on your available roof space and your house’s orientation.
If you are interested in using 100 watt solar panels for an outbuilding project at your house. You can find more information here;
I hope you enjoyed this post and have found it helpful. If you have any questions about 100 watt solar panels or installing panels to your house. Or want to leave your own personal review, please feel free to leave a comment below.
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