How Many Solar Panels to Run a Hot Tub?

Have you ever wondered how you can enjoy your hot tub without worrying about high electricity bills? 

What if solar power could be the key to your eco-friendly relaxation?

As the green energy movement gains momentum, more homeowners are turning to solar power to run their appliances, including hot tubs. 

But the question remains: How many solar panels do you need to run a hot tub?

You need around 3 300W solar panels to power a hot tub. 

However, this number can vary depending on the size of your hot tub and your local climate.

In this article, I’ll walk you step by step through the process of calculating how many solar panels you need to run a hot tub.

Key Takeaways

• To calculate the number of solar panels needed for a hot tub, first determine the tub’s energy consumption. 
• Next, assess the peak sun hours in your area, then calculate the theoretical size of your solar system. 
• Factor in system losses to get a real-world estimate.
• Finally, divide this adjusted system size by the wattage of one solar panel to find the total number needed.
• The total cost of the solar system for a hot tub can be around $1,642
• Running your hot tub with solar panels can save you around $4,406 in 25 years

How to Calculate the Number of Solar Panels You Need?

1. Calculate Your Hot Tub Energy Consumption

Before we get into the specifics of powering your hot tub with solar panels, you need to know how much energy the solar heat pumps use.

Most hot tubs require between 3.5 kWh and 6 kWh of energy to heat the water and run the jets.

Of course, this number varies based on the type of hot tub, its size, and the climate you live in.

You can calculate your hot tub’s energy needs by multiplying its wattage by the number of hours it runs each day.

My hot tub uses 5 kWh of energy to heat and run the jets, and I use it for 3 hours twice a week.

To calculate how much energy I need to power my hot tub per month:

Total energy needed per month = 5 kWh x 8 days x 3 hours = 120 kWh/month

So, I need around 120 kWh of energy per month to power my hot tub.

2. Find out the Peak Sun Hours in Your Area

The amount of energy solar panels can generate depends on the amount of sunlight they receive.

And since solar panels don’t receive the same amount of sunlight during the whole day, we turn to peak sun hours.

Peak sun hours refer to the number of hours in a day when the sun reaches its highest intensity, and the solar irradiance is 1,000W/m² per hour.

To be more clear, let’s work with an example.

Say you live in a region where the peak sun hours are 5 hours.

In this case, you can assume that your solar panels will generate about 5 kWh of energy each day (1,000W/m² x 5 hours).

To know how many peak sun hours your area receives, you can use NREL’s solar calculator.

I live in California, so I’ll use 5.83 peak sun hours per day which translates to 174.9 hours each month (5.83 x 30 days).

3. Calculate the Theoretical Size of Your Solar System

Now, we know the peak sun hours in our area and how much energy we need to power our hot tub.

So, let’s calculate the theoretical size of the solar system.

To do this, we’ll use the following formula:

Theoretical Size of Solar System in kW = Hot Tub Energy Consumption (kWh) ÷ Peak Sun Hours per Month (hrs)

So, for my hot tub that needs 120 kWh per month and the peak sun hours in California is 174.9 hrs/month:

Theoretical Size of Solar System = 120 kWh ÷ 174.9 hrs = 0.686 kW

This means that I need around 0.686 kW or 686 watts of power to power my hot tub.

So basically, three 200W panels and one 100W panel should be enough, right?

Well, not really.

You should know that this number is only a theoretical value.

We still need to account for other factors like system losses such as shading, inverter losses, age of the panels, etc.

4. Factor in System Losses

Any solar system experiences losses due to various factors like shading, inverter losses, thermal losses, dust accumulation, etc.

These losses will affect the total output of your solar panels and can vary from system to system.

In general, the industry standard is to account for a 14% system loss.

So, the real-world size of the solar system would be:

The Real Life Solar System Size (kW) = Theoretical Solar System Size (kW) x 1.14

If we plug in the numbers for my hot tub:

Real Life Solar System Size = 0.686 kW x 1.14 = 0.782 kW

This means that I need a solar system of around 0.782 kW or 782 watts to power my hot tub and account for all other losses.

5. Find the Total Number of Solar Panels

Solar panels are rated by the number of watts they can generate.

Most residential solar panels are rated between 250 watts and 400 watts.

This wattage rating indicates how much energy they can generate for every peak sun hour (1,000W/m²) they receive.

For instance, a 300W panel will generate 300W of energy per peak sun hour.

Now, let’s calculate how many panels you need for your hot tub.

To do this, divide the real-life solar system size (kW) by the wattage rating of the panel:

Total Number of Solar Panels = Real Life Solar System Size (kW) ÷ Wattage Rating of Panel (kW)

For our example, I’ll use a 300W panel:

Total Number of Solar Panels = 0.782 kW ÷ 0.3 kW = 2.6 panels ~ 3 panels

So, for my hot tub, I need around 3 solar panels rated at 300W each.

Do I Need Batteries to Run a Hot Tub on Solar?

Solar panels collect energy from the sun and convert it into electricity that can power your hot tub.

However, the sun isn’t always available and you may experience cloudy days or periods of low sunlight.

And since solar panels don’t store any energy, you’ll need a battery system to store the excess energy generated by the solar panels when it’s sunny.

To calculate how many batteries you need, you can use this formula:

Battery Size (Ah) = Solar Panel Daily Output (Wh) / Battery’s Voltage (12/24V) / DoD (0.5/0.75/0.8)

So, we first need to calculate the solar panel’s daily output.

Since we have 3 solar panels rated at 300W each:

Solar Panel Daily Output (Wh) = Number of Panels x Rated Power Output per Panel (W) x Peak Sun Hours x (1-0.14)

So, for my hot tub:

Solar Panel Daily Output (Wh) = 3 x 300W x 5.83 hrs/day x (1-0.14) = 4,512 Wh/day

Now, let’s say I have a 24V battery system with an 80% depth of discharge:

Battery Size (Ah) = 4,512 Wh/day / 24V / 0.8 = 235 Ah

So, for my hot tub, I need around 235 Ah of battery backup to store the excess energy generated by my solar panels.

How Much Does Running a Hot Tub with Solar Power Cost?

The average cost of solar power in the U.S. is around $3-$5 per watt before tax incentives or rebates.

For our example, we need around 0.782 kW or 782 watts solar system, so the cost before incentives would be:

Total Cost = Solar System Size (W) x Average US Cost ($/W) = 782 watts x $3/W = $2,346

After taking into account all the tax incentives and rebates available which are about 30% on average, the final cost of your solar system would be around:

Net Cost = Total Cost x (1- Tax Credit Percentage) = $2,346 x (1 – 0.30) = $1,642

So, for my hot tub, the total cost of a solar system with battery backup would be around $1,642.

How Much Money Will Running a Hot Tub with Solar Panels Save Me?

Running a hot tub with solar panels will save you about $4,406 in electricity bills over 25 years compared to using grid power.

To calculate the total energy consumption of your hot tub for 25 years, use this formula:

Total Electricity Produced (kWh) = Electricity Usage (kWh/month) x 25 years x 12 months

For our example, let’s say I use an average of 120 kWh of electricity per month to power my hot tub:

Total Electricity Produced (kWh) = 120 kWh/month x 25 years x 12 months = 36,000 kWh

Now, the average rate for electricity in the U.S. is around $0.168/kWh.

So, the total savings over 25 years would be:

Total Savings ($) = Total Electricity Produced (kWh) x Electricity Rate ($/kWh) – Solar System Cost ($)

Total Savings ($) = 36,000 kWh x $0.168/kWh – $1,642 = $4,406

Therefore, I can save around $4,406 in electricity bills over 25 years by running my hot tub with solar panels.

FAQs

Conclusion

As promised, we’ve walked through everything you need to know about running a hot tub with solar panels.

My recommendation? 

Go for it, but treat it as a learning experience. 

Start with the estimated number of panels, observe how they perform, and be prepared to adjust. 

This proactive approach ensures your hot tub runs efficiently, aligning with your green lifestyle.

Do you still have questions? 

If so, feel free to drop a comment below and I’ll try my best to answer.