How Many Batteries Do I Need For a 1000 Watt Solar System?

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The question how many batteries do I need for a 1000 watt solar system is somewhat vague. It could mean how many batteries are needed to provide that power, or how many batteries the solar system should have. We will answer both questions in this guide.

A 1000 watt solar system needs a 200ah battery to run for an hour. With two 300ah batteries, the system can run for up to 7 hours.

How Many Batteries are Needed to Supply 1000 Watts?

Another way to put this question is, how many batteries do I need to provide my solar system with 1000 watts? Solar panels rely on solar power of course, but if the sky is cloudy and you want to run it, how many batteries would it take?

A 200ah lead acid battery can supply 1000 watts for one hour, and large batteries can provide even more power for longer periods. If the battery is 12V that is 2400 watts, but with a 50% depth discharge only 1200 watts can be tapped. A 24V battery can also be used if your solar panel has the right voltage.

A 12V 100ah lithium battery, including the Weize LiFePO4 can supply1200 watts if fully discharged (which you can do). Here are the watt equivalent for various 12V batteries.

  • 100ah 1200
  • 200ah 2400
  • 300ah 3600
  • 350ah 4200
  • 400ah 4800
  • 500ah 6000

Any of these batteries can supply 1000 watts to a solar system. The difference is the duration. A 300ah battery with a 50% DOD has 1800 usable watts, good for an hour and half, maybe an hour and 45 minutes.

If you have two 250ah batteries, that is 500ah or 6000 watts. Even if only 3000 watts are available, the battery can carry a 1000 watt load for 3 hours. Use the guide above and you can see how many watts they can provide.

With a lithium battery it is a different story. You can fully discharge the battery, or close to a full discharge. No need to cut the usable watts in half. Though the cost is at a premium, lithium batteries are worth considering for heavy loads.

The bottom line is you can choose from a wide range of batteries. Even a 35ah battery can provide 1000 watts if you connect four, so the choice is yours. However it is better to use higher capacity batteries to save up on space.

How Many Batteries Should a 1000 Watt Solar System Have?

It depends on how many hours you need to run 1000 watts. There are many possible scenarios for this, so let us go over some of them.

The figures and calculations here use 12V batteries, so if no voltage is mentioned assume it is 12V. But you can always use a higher voltage battery bank. If you do make sure you have an MPPT charge controller to take advantage of the extra power.

Batteries Needed to Power a Solar Panel System on Cloudy Days

A 1000 watt solar system produces around 5kwh a day or 5000 watts. To take over the solar system during cloudy days, you need a battery bank that can produce 5000 watts for five hours (using the average number of sunlight hours available).

A battery bank consisting of 2 x 300ah batteries can generate 5000 watts or more. However the batteries will be completely drained, which is not recommended if they are FLA, AGM or gel.

To avoid fully discharging the batteries, you have to double the batteries to four. That is over 14,400 watts with over 7,000 watts usable per charge, enough for five hours.

You can try other battery sizes, but 300ah or 350ah is the most practical for most. 400ah and above are expensive and heavy, while anything less than 300ah will require too many batteries.

Space and weight are very important especially for RVs. You do not want to be short on power, but stocking up too many batteries will take up a lot of room. A 12V battery is around 40 pounds, so a dozen of these in your camper or house is a hassle to work with.

Batteries Needed to Pair with a Solar System

A 1000 watt solar system can run a small RV or a few appliances in a cabin or tiny house. But when the sun sets the panels will no loner produce energy. So how many batteries do you need to maintain power for the evening?

First we have to answer the following:

  • How many watts do you expect to use at night?
  • Do you have an additional power source like a generator?
  • Do you use all 5,000 watts your solar system generates?

The answers will vary from person to person. By answering these you will save yourself a lot of trouble figuring out what batteries to buy.

Watts Required. An 800ah battery bank allows you to watch up to 4 hours of TV, around two hours of laptop use and also run a fan and some LED lights.

800ah is 9600 watts. Assuming they are lead acid batteries that is 4800 watts usable. A 42 inch TV uses 120W an hour, a laptop about 200W, LED lights 100W and a fan 50-100W.

Those are 1000 watts in total. With 4800 watts available you have plenty of power to run them. You probably won’t use your laptop and TV at the same time, so that should free up more watts to run other appliances.

Of course your case may be entirely different. If you stay up late at night, binge watch, play video games etc., you will need a lot more battery power. The assumption is power consumption goes down at night when you sleep, but it may not be in your case.

The best way to figure out how many watts you need is to add up your power consumption. Combine the total watts of all appliances and devices you use after running your solar panel. Is it 5000 watts too? Is it half?

Solar power users strive to conserve as much energy as possible. You might be surprised at how much you can save when you realize that you do not really need to watch so much TV. The scenario here is just an example, and in all likelihood you will probably use much less battery power.

Additional Power Sources. Few solar powered homes rely on solar power alone. Even an off the grid system usually has a gas generator to handle the needs of powerful appliances like AC units or refrigerators. Most RVs also use generators, and if you spend a lot of time in campgrounds they can supply your camper with power.

If you have a generator or frequent RV parks, you do not need a lot of batteries. Solar panels will provide power during the day and you can stay at the campground at night and just wait for the solar panels to recharge in the morning.

If you depend entirely on the batteries to back up your solar panels, get the largest bank you can afford. You will not only be using that to power appliances at night, but it will be your primary source if solar power output is inadequate.

To be on the safe side, you should have solar panels, a battery bank and a generator. Use the generator for your fridge or other high powered appliances. Let the solar panels handle your other appliances and reserve the battery for use at night or during rainy / cloudy days.

Do You Consume All the Solar Panel Power? The primary purpose of a battery is to preserve energy produced by solar panels. If your 1000 watt solar system produces 5000 watts and you only use 3000 watts, the rest are put in the battery bank so it can be used later.

But if you consume all 5000 watts in five hours, it might be time for an upgrade. A 1000 watt array can only supply 5kwh during the summer. Production will drop to 4000 watts or lower during the other seasons. Plus there are the variable changes that occur daily, so if you always use 5kwh get a large solar array.

If you do not use 5kwh and often have plenty of power left, store them in the battery. Use the guide given above to determine battery size. Just make sure it is at least large enough to hold the solar power you want to store.

Always plan ahead. Think not just of the current season but also the rest of the year. Make room in your calculations for those times when solar power output will decrease, so you will always have enough power.


if you are going to set up a 1000 watt solar system – or any size – you have to decide right away how you will use it. This will make it easier to determine how many batteries you are going to need and make adjustments if necessary.