From backyard koi ponds to rural farms, submersible solar-powered pumps have become a go-to option for those who do not have access to municipal water or those outside the reach of electrical power grids due to geography or prohibitive cost. A solar-powered submersible pump system is a cost-effective way to address many types of water uses, but how much solar power is needed to use one?
For a typical 12 or 24-volt DC submersible pump capable of pumping two to three gallons per minute from a source of modest depth, a single 300-watt solar panel can furnish the solar power required. For greater water needs, additional solar panels will be necessary, upwards of 400-1400+ watts’ worth.
One solar panel or three? 300, 600, or 900 watts? In this article, we do a deep dive into solar pumping with a focus on determining power needs.
How Much Solar Power Does a Submersible Pump Need?
As renewable energy sources continue to develop, they are becoming viable ways to power a wide range of operations in commercial and residential settings. Solar pumping is not only cost-effective long-term; it also checks all the boxes from an environmental standpoint. Furthermore, a pumping system powered by solar energy can be deployed in areas where other energy sources may not be available.
Solar power can be used to run pumps that supply water to many areas of need and a wide range of applications. But pairing the right solar power system with the particular submersible pump being used is the only way to ensure that the targeted volume of water will be supplied and delivered efficiently and reliably.
Understanding Solar Pumping
Harnessing the sun’s power to deliver water from a source to a site where it is needed is a process that begins with planning. Part of the equation is figuring out how much solar power is needed to meet the targeted water volume. Ultimately, the most accurate estimation of the solar power needed to run a submersible pump can only be determined by examining several key factors that relate to:
- What the water is needed for (i.e., the particular application in question, be it landscape watering, livestock drinking water, domestic use, etc.)
- How much water is needed, and over what period of time (e.g., 300 gallons per day, 50 gallons per hour)
- Delivery of the water from its source to the destination (this distance can be a few feet or a few thousand feet and can involve a 200-foot deep well or a rise in elevation)
Simply put, the greater the water needs in terms of hourly or daily volume, or the more difficult the delivery of required water turns out to be. That translates into the larger and more powerful the submersible pump will have to be. Therefore, the greater the number or size of the solar panels that will be required to generate sufficient electricity. Appropriate sizing of a solar pumping system is, as a result, critical.
It should be noted that today’s submersible pumps are quite powerful and very efficient, as are modern solar panels. Even a modest submersible pump operating on direct current (DC) voltage with a flow rate of one gallon per minute (GPM) can produce over 400 gallons of water over the course of one day in most locations across the United States.
(Source: Backwoods Home Magazine)
The Solar Pumping Equation
When it comes to solar pumping systems, careful planning is an absolute must as a one-size-fits-all approach is guaranteed to result in major (and potentially costly) problems. The amount of power required by a solar pumping operation correlates directly to the particular pump that is being used, which in turn is sized by the water needs of the particular application in question.
For instance, the amount of solar power needed to run a submersible pump supplying drinking water for a large herd of cattle or providing irrigation for a substantial farming operation will differ significantly from the solar energy needed to meet the daily water needs of an off-grid residence for a family of four. Even within the same application, solar power needs will vary depending on certain conditions such as:
- Specific water volume needed as expressed in GPM (gallons per minute) or GPD (gallons per day)
- TDH (Total Dynamic Head), which is basically the sum of the vertical distance (elevation) and resistance (friction) within the water piping that the pump must overcome to effectively deliver water to the desired destination (more on this later)
- HorThe horizontal distance between the water source and the destination (this relates to friction in the water pipes that will hinder water flow)
- Conditions of water consumption (e.g., continuous, sporadic, surge, etc.)
These are but a few of the more common factors that affect how much solar power is needed to run a submersible pump. Depending on the operation’s particulars, other conditions could come into play, such as:
- Geography (local terrain)
Thus, while one particular application may get by with a single 100-watt solar panel, another may require an entire array of them.
(Source: Leaf House tea)
How Solar Power for Pumping is Determined
Every solar pumping project begins with an earnest assessment of projected water needs, whether calculated as a daily figure or hourly. A major distinction can be drawn between solar pumping for a residence or homestead or for a commercial enterprise where water consumption can be enormous such as:
- Livestock operation
It is worth noting that even within the context of exclusively domestic use (i.e., household water usage only), American families’ average daily water consumption is well over 130 gallons. This excludes water used to maintain landscaping, washing cars and other vehicles, and other outdoor water usages.
Projecting Water Consumption
Within a residential setting, these are commonly used figures for routine, everyday activities involving water consumption:
|Toilet Flushing||33 gallons per day||Water Leaks||18 gallons per day|
|Showering||27 gallons per day||Bathroom Faucet||4 gallons per day|
|Kitchen Faucet||27 gallons per day||Dishwasher||2 gallons per day|
|Washer (Laundry)||22 gallons per day||Other/Misc.||4 gallons per day|
|The average American household uses approximately 137 gallons of water per day.|
(Source: Water Footprint Calculator)
By comparison, water consumption in an agricultural (including livestock raising) setting is immensely higher. To illustrate, the daily amount of water to sustain four milking cows is equal to the average daily water consumption for an entire household (which includes showering, toilet flushing, doing the laundry, washing the dishes, etc.).
|Milking cows (ea.)||35 gallons per day||Chickens (100 ct.)||9 gallons per day|
|Sprinklers (cooling)||20 gallons per day||Bulk tank washing||30-40 gallons/wash|
|Horses (ea.)||12 gallons per day||Irrig. – Sprinkler||4,000 g./day/acre|
|Sheep/goats (ea.)||2 gallons per day||Irrig. – Drip||1,000 g./day/acre|
These figures reveal how vital and potentially life-sustaining of a measure solar pumping can be when deployed in areas of particular hardship and need. At the very least, a solar-powered submersible pump can result in potential savings of the thousands of dollars it can take to bring metered electricity to a rural or undeveloped site.
(Source: Homesteading Today)
Calculating Gallons per Minute
Depending on the location, a solar day (when energy-convertible sunshine is brightest) can last approximately six hours. Using the household example, dividing 137 gallons (a day’s water consumption) by 6 hours equals 22.8. Dividing this figure by 60 minutes equals .38.
This means that in order to sustain an average American household’s water needs daily, a solar pumping system must provide .38 gallons per minute.
A larger-scale operation like irrigating an acre of farmland with a drip system can be calculated in a similar fashion. Starting with 1,000 gallons and dividing it by 6 hours equals 166.67. Dividing this figure by 60 minutes equals 2.78, which indicates that to supply adequate water for this application, a properly sized submersible pump will need to deliver a minimum of 2.78 gallons per minute for a full six hours straight.
There are variables at play in any solar water pumping scenario, so the amount of solar power needed for a submersible pump to run properly truly depends on the particular circumstances involved. Fortunately, pump manufacturers and solar panel fabricators have standardized their offerings to a large degree, streamlining the process of pairing these vital components together.
Submersible Pump Ratings
When figuring out how much solar power is needed to use a submersible pump, the first part of the equation is the pump itself. All pumps, regardless of the type or make, are rated by their manufacturers according to various parameters that help operators determine their suitability for particular tasks and operations. This data can be quite voluminous, but the key figures with respect to solar pumping are:
- Maximum GPM (Gallons per Minute) – this is the pumping rate at which the system will produce usable water (GPM can be used to calculate gallons per day, which is another common way to indicate a solar pumping system’s productivity)
- Maximum Head or TDH (Total Dynamic Head) – this is essentially the resistance that a pump will encounter when moving water from its source to the destination (in other words, how hard it will have to work to perform its job)
- Volts (voltage) is an indication of the electrical force needed to run the pump
- Watts (wattage) is an indication of the electrical power needed to run the pump
The first two parameters of GPM and TDH relate to the submersible pump’s ability to push a certain volume of water at a particular rate over a specific vertical and horizontal distance. Provided that the pump’s electrical requirements are met, GPM indicates the water production that can be expected. At the same time, the TDH represents the resistance that the pump can withstand or overcome in performing its job.
(Source: altE Store)
Voltage and wattage indicate the pump’s electrical requirements to perform its functions as intended. A common analogy used to explain electricity is to compare the flow of electrons through a wire to water flowing through a pipe. The voltage is the water pressure in the pipe (energy potential), while the wattage is the amount of power that the water in the pipe can exert.
A watt is a unit of energy that can be expressed in various ways, but in the case of solar pumping, it pertains to the amount of solar energy used by a submersible pump and also the amount of power produced by a solar panel. In lower capacity systems, the term watts is used, while in larger systems, the term kilowatt (kW), corresponding to 1,000 watts, may be more common.
Solar Panel Ratings
Watts and volts are not only how the electrical needs of submersible pumps are expressed; they are also how the output of solar panels is commonly indicated. As with the needs of most submersible pumps, the electricity produced by solar panels is DC or direct current. This electrical alignment enables these pumps to be directly powered by solar panels without the need for an inverter in the case of AC-powered pumps or the use of batteries.
Solar panels are comprised of photovoltaic (PV) cells that harness sunlight and convert it into electricity. Panels can be connected in a series to yield greater output to increase power production. It is the modular nature of solar panels, where they can operate alone or as part of a chain, that provides a tremendous degree of flexibility for power requirements, small or large.
Although low-wattage (less than 100 watts) solar panels are available (particularly those that are designed to be portable), most modern panels are configured with either:
- 60/120 PV cells – on average, these panels measure 66 inches by 40 inches with a 1.4-inch thickness and weigh approximately 40 pounds
- 72/144 PV cells – on average, these larger panels measure 80 inches by 40 inches with a 1.4-inch thickness and weigh in at approximately 54 pounds
In the case of pumping, solar panels not only represent a viable power source for even the remotest of operations (there are even portable panels that can be folded up) they are also completely scale-able for the most modest of water needs up to large-scale, heavily water-dependent applications like:
- Just about everything in between
Putting it all Together
Once a pump is properly fitted to a particular pumping operation as far as the water volume that is needed, the other part of the equation – pairing the pump with the right solar panel array – can be addressed. This process involves matching up water consumption with pump performance and then cross-referencing against solar panel output.
This table shows a variety of submersible pumps encompassing a range of:
- Water pumping capacities
- Corresponding power requirements
Also indicated are the maximum head, or TDH, values. As is evident from this data, larger pumps require more power but can pump more water. (It is worth noting that the lower the TDH, or resistance, the higher the GPM.)
|2.4 to 4.5 GPM||20-140 watts||12-30 volts DC||100-230 feet|
|1.3 to 5.0 GPM||95-184 watts||12-30 volts DC||115-230 feet|
|3.0 to 11.0 GPM||900 watts||30-300 volts DC||325-525 feet|
|10.0 to 45.0 GPM||1200 watts||24-48 volts DC||165-760 feet|
|25.0 to 75.0 GPM||1400 watts||30-300 volts DC||50-100 feet|
(Source: Colorado State University – Extension)
Modern PV solar panels are typically comprised of 60/120 or 72/144-cell configurations with voltages that vary from 12 volts DC up to over 40 volts DC, and wattages that can range from under 100 to over 400 watts per panel. Thus, pairing solar panels with submersible pumps becomes a matter of matching up the targeted water delivery (GPM) with the proper voltage and wattage range.
It is not uncommon for multiple solar panels to be installed as part of an array in order to satisfy the wattage required by the pump. For instance, if daily water demand for an operation requires a delivery rate of 5 GPM and the submersible pump draws 900 watts, it will likely be necessary to set up an array of three solar panels, each rated for a minimum of 300 watts of output.
(Source: The Solar Store)
Key Tips for Optimizing a Solar Pumping System
While the concept underlying solar pumping is fairly clear-cut, and the installation of components relatively straightforward. However, without proper planning and forethought, various problems can arise, such as the pump failing to lift water from a below-ground source like a well or the solar panels failing to provide adequate electricity to power the pump.
A solar pumping system may appear to work fine on the surface (no pun intended) but may not be optimized and, in fact, could be working harder than it needs to, resulting in faster wear of system components.
Modern technology has made both pumps and solar panels highly efficient and operator-friendly. Still, there are certain techniques and strategies that can enhance the conversion of sunlight into electricity by solar panels and improve the performance of submersible pumps. Here are few key tips for ensuring the longevity of solar pump and panels and for optimizing the performance of a solar pumping system:
- Installing solar panels in series or parallel – to increase the overall power of a solar pumping system, individual solar panels can be installed in series or parallel to satisfy the electrical requirements on the pumping side. Wiring panels in series results in the entire array producing the sum of all panel voltages (e.g., 12 VDC + 12 VDC = 24 VDC) but having the amperage of one (e.g., 5 amps).
Wiring solar panels in parallel will result in the entire array producing the voltage of one panel (e.g., 12 VDC) but with amperage that is the sum of all panels (e.g., 5 A + 5 A = 10 A).
The wattage for a solar panel array is always the sum of the individual panels’ watts produced.
(Source: University of Tennessee – Extension)
- Proper orientation of solar panels – even though modern panels are more efficient than ever before at converting sunlight into electrical power, properly orienting and aligning solar panels will ensure that solar power conversion is optimized.
For starters, solar pumping systems installed in the U.S. (or anywhere in the northern hemisphere for that matter) should face true south for optimal sunlight exposure. Solar panel arrays installed at or near ground level are more easily cleaned (e.g., brushing off leaves and other loose obstructions). Tilt angles can also be optimized and correlate to latitude and time of year.
(Source: NYSERDA – New York)
- Oversizing the solar panel array – as a general rule of thumb, it is recommended that the wattage of solar panel arrays (the sum of the watts produced by the individual panels) be sized 20% to 25% greater than the wattage specified for the submersible pump. This is particularly true if the panel array will be directly wired to the pump.
For instance, a 100-watt submersible pump should be connected to a solar panel array capable of generating 120 to 125 watts at a minimum. The extra wattage translates to greater panel surface area, which will pay dividends in low sunlight conditions such as mornings and late afternoons while also serving as a booster to get the pump started for each day’s pumping.
(Source: University of Vermont – Extension)
- When possible, go with submersible pumps – for applications involving deeper water sources such as below ground wells, lakes, and ponds, solar-powered submersible pumps are the ideal choice.
Submersible pumps lie within the medium (e.g., water) being pumped and are therefore considered to be more efficient than surface-mounted pumps because the pressure of the surrounding liquid at the pump intake naturally feeds the pump. Hence, all it needs to do is push the material to its destination. Most are direct current and can therefore be directly wired to panels.
(Source: Advanced Power)
- Water storage – although today’s solar pumping systems are more efficient than ever before, they can be scaled in size to meet a wide range of water needs. It may be prudent to incorporate water storage in the form of a tank into the system for certain types of operations.
Certain applications require an uninterrupted supply of water. The rule of thumb is to size the storage tank to hold a full three days’ supply of water in the event of a system malfunction or unforeseen circumstances such as weather or other natural disasters. Depending on the specific location, steps may need to be taken to freeze or frost-proof the tank and its piping.
(Source: U.S. Department of Agriculture)
- Integrate pumping into a larger solar energy plan – as more home and property owners embrace the financial and eco-friendly benefits of solar energy, there is greater independence from utility-provided electricity to power electrical devices, appliances, and equipment.
The same roof-mounted solar panel system the provides electricity to keep a household running can be used to power water supply and delivery at sites where a reliable source of water exists. In such instances, this may create an opportunity to live an off-grid existence without sacrificing any of the creature comforts of the modern lifestyle.
Even the world’s foremost manufacturer of electric vehicles is realizing the incredible potential of solar energy. Tesla’s Solar Roof dispenses with the bulky and unsightly to some, solar panels that are becoming a common fixture on rooftops around the country. It replaces them with roof tiles that are actually fully functional, mini solar panels for a solar-enabled roof that hardly looks the part.
Best of all, Tesla touts the cost of its solar roofing shingles as far less expensive per watt than conventional solar panels. The only question that remains is when they will be widely available.
(Source: Energy Sage)
Other Solar Pumping Applications
The very nature of solar pumping means that an efficient and highly productive water delivery system can be deployed in just about any area where the combination of source water and sunlight exists. This translates to a wide range of activities and applications where solar pumping may be the ideal, if not the only, option.
Aside from operations like farming, agriculture, livestock, and domestic use, other applications that can benefit from solar pumping include:
- Disaster recovery – with the advent of portable solar panels (which can even be folded and transported in a carrying case), deploying a solar pumping system in areas hard-hit by flooding caused by natural disasters can pump standing water in a pinch when electrical service has been interrupted or when gas-powered generators may not be feasible.
- RV living – for those who live in RVs part-time or full-time, for leisure or out of necessity, solar-powered pumping can connect people with a reliable means of obtaining water for cooking, cleaning, and other life functions.
- Pond and backyard water features – whether purely decorative or semi-functional as a watering hole for neighborhood critters, backyard ponds and water features are vulnerable to significant water loss through evaporation in hot and dry weather. Depending on the location, upwards of 2 inches of depth can be lost in a single day through evaporation. (Source: SF Gate Homeguides)
If a source of replenishing water lies nearby, a solar pumping system can be a gamechanger as far as pond management is concerned. Best of all, such a system would be virtually maintenance-free as its inherent design assumes self-operation.
Solar pumping systems are a perfect marriage between two vastly different but equally critical resources: renewable energy from the sun and the precious, life-sustaining resource of water. Thanks to modern technology and human resourcefulness, the power contained in sunshine can be harnessed by solar panels to provide water in even the remotest and harshest of environments.