Sump pumps are essential to your home’s drainage system. They help keep water out of your basement by automatically pumping it out when water gets too high. A sump pump can prevent serious damage and prevent flooding from occurring in your basement during heavy rainfalls or other potentially damaging weather events. 

During flooding power from the grid may be cut off and you’ll need a backup system to run your sump pump. Solar power is a good option as you can rely on energy from the sun. In this article, we look at the power requirements of a sump pump, the battery bank, and the number of solar panels to run your sump pump. 

Solar Power for an 800-Watt Sump Pump 

The amount of power required to operate a sump pump depends on a number of factors, including:

• The size of the pump (smaller pumps can use less power than larger pumps)
• The type of motor used by the pump (a permanent magnet motor uses less energy than an induction motor)
• The length of time that pumps are operated each day (longer periods will result in higher energy consumption)
• How much water is being pumped out each day (the more water that needs pumping, the greater the overall energy consumption)

A 1 horse-power sump pump will need 800 Watts to Run and around 1500 watts to start. So how much solar power will you need?

To run an 800-watt sump pump you will need a 24v lithium battery rated at least 150Ah. This battery can provide the 30 amps an hour pull from the sump pump and can support it for 5 hours. With the addition of two 200-watt panels and a 24v 150Ah battery, you can run a sump pump for 8 hours. To run the same sump pump for 24 hours you will need six 200-watt solar panels and a 450Ah Lithium battery. 

Sump Pump Watt-Hour Requirement 

Electrical energy is measured in Watt-Hours. The amount of time you run an appliance determines how much power it uses.

To calculate Watt-Hours you multiply the Wattage of the device or appliance and multiply by the number of hours you use the device. 

Watt-Hours = Watts X Hours 

If you use an 800 Watt sump pump for 1 hour, you will need 800 Wh of energy. 

How many Solar Panels to run a Sump Pump 

The size of the solar array is dependent on the area, altitude, and how far you are from the equator. If you are in an area that receives around 4 hours of sunlight a day you will divide the total Watt-hour requirement by this number. 

800Wh/4 = 200 Watts 

So is a 200 Watt Solar Panel enough to support our sump pump?  Not really as the solar battery determines everything. You will also need to size up the solar array because of efficiency losses. So in this case you should go for a 400-watt solar panel or two 200-watt solar panels. 

What Size battery for a Sump pump 

From the example above we’ve seen, we’ll need around 1500 Wh in order to run a sump pump for 1 hour. In order to get the size of the battery, you would need to run the TV you will need to get the number of amps required.  

To get the number of amps the Inverter will draw from the battery in order to power the Sump pump you divide the Watts by the voltage of the system. 

For a 12v system 

800W/12v = 66.67 amps

For a 24V system 

800W/24v = 33.33 amps

Amp-hours is 1-amp of power expended over one hour. This can tell you if a battery can work for the intended use or not. 

Batteries are not designed to be depleted over a short period of time. Most solar batteries are labeled deep cycle and are intended to be used over a 20-hour period max.  But with LiFePo4 batteries, it is possible to stretch these limits as they have a 1C C rating which means you can discharge the whole battery at once. This is not recommended however but a 50% discharge in one hour is possible. 

If we are looking to support 67 amps you will need a 12v  battery that is at least 300Ah or a 24v battery that is at least 150Ah. While this battery is the least requirement for an hour it can support the sump pump for at least 4 hours. 

If we add the two 200-watt  solar panels during the day it can add 30 amps an hour to fully recharge the battery over 5 to 6 hours. So with two 200-watt panels and a 24v 150Ah battery, you can run a sump pump for 8 hours. 

Inverter for 800-watt Sump Pump

An inverter converts the dc power from the battery to AC power to be used by the sump pump. When you are choosing an inverter you match the wattage of the appliance to the inverter. However, when matching your sump pump to an inverter you need to be aware of the starting wattage. An 800-watt sump pump will have a starting wattage of around 1500 watts. 

For this sump pump, you will need an inverter that is at least 1600 watts. 

How Much Solar Power to run a sump pump for 24 hours?

Depending on your flooding situation and the rainfall you are receiving you may need to run your sump pump for longer hours. So how much power will you need to run your sump pump for 24 hours?

We have already estimated the requirements for an hour. And we’ve got the solar panels and batteries that can run an 800-watt sump pump for 8 hours. So how many solar panels and batteries to run the sump pump for 24 hours? 

Let’s add capacity to our battery first, in order to add reserve capacity we can go three times.  So for our 24v battery, we’ll need a 450Ah Lithium battery.  This battery can only still run the sump pump for around 13 hours. 

You will need a add solar panels again going three times what we had earlier estimated you will need six 200-watt solar panels. These solar panels can fully recharge the 450Ah in the course of a day. This can add capacity to run the sump pump for 24 hours. 

Conclusion

In case of flooding in your basement, you may need to run your sump pump for long periods of time. The amount of power a sump pump uses depends on the size and type of pump. Some pumps are designed for light use, like a backup system for when your main pump breaks or for small basements. Others are designed for heavy use, like pumping water from large basements or other areas with large amounts of water.  Solar panels and batteries can be used to run your sump pump for up to 24 hours.