How much solar does an aquaponics or hydroponics system need?

The appeal of solar-powered growing is simple: the system runs off the same energy source the plants use. The economics work only if you know what the system actually draws, and most people underestimate the load.

Calculating the daily load

Every electrical component in the system has a wattage and a daily runtime. Multiply and sum to get watt-hours per day (Wh/day).

Water pump. A typical aquaponics circulating pump draws 15-40W. If it runs continuously: 30W x 24h = 720 Wh/day. If it runs on a timer (15 min on, 45 min off): 30W x 6h effective = 180 Wh/day. The timer method cuts pump energy by 75%.

Air pump. 3-10W, runs 24/7 for fish aeration. 5W x 24h = 120 Wh/day. Small draw but it never stops.

Heater. The variable that dominates in cold climates. A 200W aquarium heater in a 200L tank heating from 15°C ambient to 26°C (tilapia range) runs roughly 50-70% of the time in winter. 200W x 0.6 duty cycle x 24h = 2,880 Wh/day. That's four times the pump and air pump combined. In mild climates or summer, the heater barely runs. In cold climates in winter, it's the largest load by far.

Grow lights (indoor systems only). A 150W LED panel running 16 hours: 150W x 16h = 2,400 Wh/day per light. Multiple lights multiply accordingly. Indoor hydroponic systems with grow lights are the most power-intensive setup. A greenhouse or outdoor system avoids this entirely.

Other. Fans, monitoring equipment, automatic fish feeders: usually under 50 Wh/day total.

Example: outdoor aquaponics in a mild climate

Water pump (30W, continuous): 720 Wh/day. Air pump (5W, continuous): 120 Wh/day. Heater (200W, 30% duty in mild winter): 1,440 Wh/day. Total: approximately 2,280 Wh/day, or 2.3 kWh/day.

Example: indoor hydroponics with grow lights

Water pump (15W, timer): 90 Wh/day. Air pump (5W, continuous): 120 Wh/day. Two 150W LED panels (16h): 4,800 Wh/day. Total: approximately 5,010 Wh/day, or 5.0 kWh/day.

The grow lights dominate. Reducing light hours or using fewer panels has the largest impact on solar array size.

The daily load calculator adds up the individual components for your specific system.

Sizing the solar array

Solar panels are rated in peak watts (Wp): the output under ideal conditions (1000 W/m2 irradiance, 25°C cell temperature). Real-world output is lower. The conversion factor is peak sun hours (PSH): the number of hours per day at which the panel effectively runs at rated output.

PSH varies by location and season:

Southwest US desert: 5.5-7 PSH (summer), 3.5-5 (winter)
Midwest US: 4-5 PSH (summer), 2-3 (winter)
Pacific Northwest / UK: 3-4 PSH (summer), 1-2 (winter)
Tropical latitudes: 4-6 PSH year-round

To size the array: Daily load (Wh) / PSH / 0.85 (system losses from wiring, inverter, temperature derating, dust) = required panel Wp.

Example: 2,300 Wh/day load in the Midwest US with 3 PSH in winter (sizing for the worst season): 2,300 / 3 / 0.85 = 902 Wp. Two 450W panels or three 300W panels.

In summer with 5 PSH, the same array produces 5 x 902 x 0.85 = 3,834 Wh/day, well above the 2,300 load. The surplus charges batteries for cloudy days.

The solar array calculator runs this math with your specific location's PSH data.

Battery sizing

A solar-powered growing system needs battery storage for nights and cloudy days. How many days of autonomy to plan for depends on climate.

The baseline: enough battery to run the system through one night (12-16 hours at the nighttime load). At night, grow lights are off (if any), the heater runs (if cold), and the pump and air pump run continuously.

Nighttime load for the outdoor aquaponics example: pump (30W) + air pump (5W) + heater at 50% duty (100W effective) = 135W x 12h = 1,620 Wh. A battery bank of at least 1,620 Wh usable capacity covers one night. For lead-acid batteries at 50% depth of discharge, that means 3,240 Wh rated capacity. For lithium (LiFePO4) at 80% depth of discharge, 2,025 Wh rated capacity.

For cloudy-day autonomy (2-3 days without sun), multiply accordingly. The battery bank calculator computes the required capacity for your load and desired autonomy.

When solar doesn't make sense

If the system runs indoors with grow lights, the solar array needed to power the lights is large. Two 150W panels running 16h/day is 4,800 Wh/day of load, requiring 1,600-2,300 Wp of solar panels (depending on location). That's 4-6 residential-size panels, a battery bank, an inverter, and thousands of dollars in equipment. For comparison, the grid electricity to run those lights costs modest monthly grid electricity costs. The payback period exceeds 10 years.

Solar makes the most economic sense for outdoor systems where grow lights aren't part of the load: outdoor aquaponics, greenhouse hydroponics, or pond systems. In those cases, the daily load is 1-3 kWh, the solar array is 2-4 panels, the battery bank is modest, and the payback period is 3-5 years against grid electricity.

The system cost calculator estimates the upfront cost and payback timeline for a specific configuration.