40 Watt Solar For RV: What Can a 40-Watt Solar Panel Power?

Alternative power sources come in handy. When you want to run smaller electrical items, having a secondary power source will help. The key is to make sure that the power source will provide enough energy to power those items. Add up the wattage of the items you want to power to see if this strategy will work for you or not.

What can a 40-watt solar panel power? With 40 watts at your disposal, you may be able to run some lights, a window fan, and even a water pump. The solar won’t power big-ticket appliances, etc. but it can give you about 2 to 2 1/2 amps on a good sunny day.

To learn what this size of solar panel can power, just continue to read our article. It has the information you need to help you save energy where you can. Take a few minutes to see if this information is helpful to your camping situation.

What Is a 40-watt Solar Panel Good For?


On a good sunny day, a 40-watt solar panel can generate about 40 watts per hour. if you have 7 hours of sunlight that means you can have roughly 238 watts available to power smaller items.

Yes, 7 x 40 is 280 but you need to factor in about 15% for energy loss. This amount of energy is what is saved in your battery when you do not use it to power those devices that do not need a lot of power to work.

That energy saving gives you power when you need it. You may not be able to recharge your battery with a 40-watt solar panel, but you certainly can keep the power in the battery in reserve. When emergencies take place, you will have the power there waiting to be used instead of being used up earlier in the week.

Then, the solar panel is good for keeping lights lit at night. The stored power will provide the energy needed to keep your outside lights on. That will help keep your camping spot more secure.

Or if you need cooling, it will power a nice window fan or even let you make some cool ice tea on a hot day. The panel willpower your water pump making sure you have water when you get thirsty.

There are lots of areas where the 40-watt solar panel can come in handy.

Will a 40-watt Solar Panel Charge a 12-Volt Battery?

It can but you may be waiting up to a week or more before the battery gets recharged. The amount of amps produced by this size of solar panel is about 2 to 2 1/2 per hour. That is about 1/10th of what you need to recharge a battery quickly.

If you are in a hurry, you would need up to 20 amps per hour to recharge the battery within 5 hours. To get 20 amps an hour, you would need either 3- 100 watt solar panels or 1- 300 watt solar panel.

The 40-watt is just too weak to do a good job or even do a bad job slowly. Of course, those figures will be a bit flexible depending on the make and model of the battery. The calculations made here are based on recharging a 100/h battery.

For a 200 ah battery, you will most likely need more power. That is unless your 100-watt solar panels do not reach 30 amp per hour production. Then the next key will be the type of day you are experiencing.

Those figures are given under ideal conditions. A cloudy or rainy day will see your amp production drop considerably.

40w solar Panel Battery Size


While there are different size batteries, you do need to find the right one for your solar panel. If you get 57 hours of sunlight you are looking at generating roughly 200 to 280 watts of power minus 15% approx.

The minimum battery you would need to store the energy would be a 40ah size. This battery can be recharged in one day if you get the sunlight for that amount of hours. Then once the power is in the battery you can power a few items all night long.

To help make the power last, you can change your regular lights to LEDs and use less power. Plus, you can charge a fan or run a small television set. You will have to stay small as the larger appliances, including an induction cooker, will drain the battery just starting up.

A 40-watt solar panel is just an accessory to help you conserve main battery power. It is a useful tool, not the primary power source unless you are really roughing it and cooking outside over a campfire.

Also, it is a good backup power source when your main battery runs out and you still need lights and a little water, etc.

How Long Does It Take a 40-watt Solar Panel To Charge a Battery?

Two main factors in this process will determine the length of recharging time. One factor is the sun. If you get a lot of it, for example, in the middle of the summer where the sun stays out late, then the recharging time will go a lot faster.

If you get a lot of cloudy weather and rain, or you are trying to recharge in the winter, then the recharging times slows way down. The lack of sunlight will not give you the power you need.

The second main factor will be the size of the battery. The larger the size the more amps you will need and a 40-watt solar panel doesn't pull a lot of watts every hour. While you can recharge a 40ah battery in one day with up to 6 hours of sunlight, a 100ah or a 200 ah battery needs more amps per hour and will take a lot longer to recharge.

Then if you lose sunlight during that period, you will need to be patient as the recharging time will be extended. A third factor in recharging a battery will be the number of amps you are drawing every hour.

The more amps you get, the faster the recharging will go. If you are trying to recharge a 100ah battery and you are getting 20 amps per hour, then it will take 5 hours to recharge the battery.

But 40-watt solar panels cannot reach that level on their own. They will need help.

How Many Amps Does a 40-watt Solar Panel Put Out?


In full sun, the number of amps you will get each hour will be between 2 and 2 1/2. If the sun does not stay out for long periods, that production will go down. If the sun stays out for about 8 hours and is not blocked in any way, then you can expect to receive 16 to 20 amps for the day.

This figure is not bad as on average most portable 100-watt solar panels only produce up to 5 to 6 amps every hour. That means you are only getting between 17 to 18 volts. if you want more power, then you would need to abandon the 40-watt strategy and upgrade to a solar panel that puts out more power.

For example, a 400-watt solar panel can produce up to 26 amps approx., every hour. All these figures are given under ideal conditions. You would have to figure out how many amps per hour you would need to power your electrical devices and see if the 40-watt option is the right choice for you.

No matter what you do, you will not escape the need to do some math at some point in time.

40-watt Solar Panel For RV


The good thing about these smaller portable solar panels is that you can get them in a variety of formats. Amazon alone has about 5 or so different designs. These designs help you capture the sun’s rays from any direction.

That means you can store more power and do not have to go out and keep changing the position of the panel. Just find the best spot and leave it. The cost of these panels is reasonable and affordable.

The thing about using solar panels is that they are not really needed unless you do a lot of boondocking. They really do not help you when you have access to shore power.

The bad news is that the 40-watt models are not showing up on most top 10 or best solar panels lists. You will have to rely on reviews of individual panels or talk to the experts in your local stores. They will turn you on to the right brand and model or set you on the right search path.

Usually, the majority of owners like the larger panels that provide more wattage. their needs are greater than others and they need more power to run their necessities. The larger panels may cost more but they may be better in the long run.

Coleman 40w Folding Solar Panel Review


The fold-out design makes installation a little easier to get done. The panel itself uses crystalline solar cells and a durable metal frame to capture that free energy. It is an all-weather solar panel so you can leave it set up when the weather changes on you.

The overall opinion that we could see is that the 40-watt Coleman or any 40-watt solar panel is going to be on the not enough side of the power game. When your electrical needs are small, these are good panels to have along for the ride.

But because they are so limited in producing power, they may become a waste of space when you need more power. You are only getting 40 watts and that production is under ideal conditions.

Even if you are frugal, you may find that this is not an ideal size of panel to have on hand. Coleman is a fine brand to work with and your experience with the company and its customer service will determine if you buy it or not.

This panel is efficient and does the job it is supposed to do but again, the amount of power you get is going to be minimal and not enough. The final consideration here will be the price. It is selling at Canadian Tire for over $250 and sometimes it will go on sale.

But is the expenditure worth it when you may get larger panels for about the same price or just a tad bit more?

Pros And Cons Of Using a 40-watt Solar Panel


  • You can save some power- it may not be much but the extra power can come in handy.
  • They are affordable- when you are on a tight budget, their price can still fit that restriction.
  • They are easy to set up- plus they come in different designs to maximize their energy getting capacity.
  • They are small- that makes them easy to store and carry to where you want them set up.


  • They do not produce a lot of power- this is good in some cases but not all.
  • They are not good for campgrounds with shore power- their use can be restricted as well unless you want to save onshore power expenses.
  • They may not be worth the money- it will depend on your purpose to figure this one out.

Some Final Words

Solar power can be advantageous but only if the power produced will meet or exceed your needs. You would have to figure out your purpose and then do the math to see if buying one of these is worth the expense. Sometimes going larger and getting more power than you need is better than shorting your power supply.

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