Choosing a solar system for your RV, cabin or home is not always straightforward and can be complicated by the various options available on the market.
While there are many reliable solar systems available, performance alone is no longer enough, it is important to know if it is worth the investment.
For example, you may be wondering if a 4 kW solar system is worth the investment, what benefits you can expect from it, and how long you can expect to break even with it.
So in this guide, I discuss whether a 4 kW solar system is worth it.
I also share some information to help you get started with selecting the right capacity of components – the number and size of batteries.
Lastly, I also share examples of appliances that you can connect to make the most of your 4 kW solar system investment without damaging it.
Is it Worthwhile Investing in a 4 kW Solar system?
If your goal is to save money then a 4 kW Solar system will save you about USD 2 per day or about USD 60 per month.
This assumes that the system generates about 16 units (16 kWh) of electricity a day valued a 13 cents/kWh.
If you assume that a complete system – solar panels, batteries, charge controller, inverter system costs about USD 5,000 plus installation, then you are looking at a payback period of about 7-10 years without subsidies.
Keep in mind that at about the 7-year mark you’ll need to invest in a new set of batteries to replace the aged ones so that the system continues to perform reliably.
Is it worth it?
In my opinion, no, unless there are subsidies or other benefits to you, for example, if it is important to you that you are using a clean, renewable source of power that also requires little maintenance.
How Many Batteries Can You Use for a 4 kW Solar System?
You can choose from several different battery configurations that may vary according to the capacity of the battery you use, the battery chemistry (lead-acid or lithium), the battery bank voltage, and the overall battery bank capacity.
A few possible battery setups that you can use are shown below but note these are just a few out of several possibilities.
The battery bank voltage used here is 48V DC.
AGM or GEL Batteries
4,800 Wh Battery Bank consisting of:
8pcs of 100 Ah batteries. You can connect them such that you have 2 strings connected in parallel of 4pcs of 12V AGM or GEL batteries connected in series for a 48V bank.
You could choose to use 200Ah batteries instead to store about 9.6 kWh from the solar panels but this will double your investment cost in batteries.
4,800Wh battery bank consisting of:
8pcs of 50 Ah batteries. You can connect them such that you have 2 strings connected in parallel of 4pcs of 12V lithium batteries connected in series for a 48V bank.
you can also use a single pylontech Lithium battery of 3.5 kWh.
4 kW Solar System | What Appliances Can you expect to Run
You can use a 4 kW solar system to power many appliances in the home such as a washing machine, fridge, water pump, water heater, AC, TV lights, coffee maker, laptops, and others as long as
- The inverter’s continuous and surge power consumption is not exceeded.
- The total daily energy consumption of the connected appliances does not exceed the energy generated and stored by the batteries.
How long the appliances can run for
The connected appliances will run for a longer or shorter duration before the available battery capacity is depleted depending on the charge in the battery, its capacity, and the combined power consumption of the connected appliances.
You can increase the runtime of the appliances connected to the system by using a large capacity battery or reducing the number and capacity (w) of appliances that are connected to the battery at any one time.
To give you an idea of what runtimes you can get and the range of appliances you may be able to connect to the solar panel, we have used a battery bank capacity of 4.8 kWh as an example.
- Washing machine: 300 watts, 1 pc for 3 hours = 900 watt hours
- Fridge: 180 watts, 1 pc for 9 hours = 1,620 watt hours
- Lights: 10 watts, 9 pcs running for 5 hours = 10 x 9 x 5 = 450 watt hours
- Tv: 50 watts, 1 pc running for 4 hours = 50 x 1 x 4 =200 watt hours
- Laptop: 40 watts, 1 pc for 5 hours = 40 x 1 x 5 = 200 watt hours
Total = 3,370 watt hours which can be accommodated by the 4,500 Wh battery.
Total power consumption is 660 watts which can be handled by a 3,500 watt rated inverter.
Important to note that the combined surge rating should not exceed approximately 7,000 watts, the estimated surge rating of a 3,500 watt inverter.
Check your inverter’s owner manual for its surge rating.
How Many Solar panels you Need for a 4 kW Solar System?
How many solar panels you need will depend on the capacity of the solar panel you build the 4 kW solar system around.
For example, you can use 10 pcs of 405 W solar panels for the 4 kW system or 20 pcs of 195 W solar panels (5 parallel strings of 4 pcs of the 12V solar panels connected in series).
These are just but 2 of the possible setups you can have.
Can a 4 kW Solar System Run an AC?
Yes, it can run an AC provided its continuous and surge power rating does not exceed what the inverter can handle.
The estimated runtime of the AC depends on the battery capacity, state of charge of the battery, the AC’s power rating, and the combined current draw from the battery.
Make sure that the AC is rated for a 115V for it to work with the 110/115V inverter output.
Will a 4 kW Solar System run a Home?
Yes if the total energy demand of the connected electrical appliances in the home is about 16 kWh or less and you have provided enough battery storage to power the appliances during the night.
That said, it is likely to fall short of meeting the energy demands of an average house in the United States.
According to the United States Energy Information Administration (USEIA), the estimated daily energy consumption of an average house in the US, in 2020 of about 30 kWh.
You’ll likely need a larger system as a 4 kW system can only meet about 53% (16 kWh) of the estimated 30kWh.
How Many Units of Electricity for a 4 kW Solar system?
*Note: This is an estimate and largely depends on how many hours of sunshine your location receives
Estimated Annual electricity output
A 4 kW solar system can generate an estimated 4,320 – 5,760 kWh of electricity annually assuming your location receives about 3 – 4 hours of sunshine.
Estimated Monthly electricity output
A 4 kW solar system can generate an estimated 360 – 480 kWh units of electricity per month assuming your location receives about 3 – 4 hours of sunshine.
Estimated Daily electricity output
A 4 kW solar system can generate an estimated 12 – 16 kWh units of electricity per day assuming your location receives about 3-4 hours of sunshine.
Monthly electricity output
To get as much power as possible, the solar panels should be angled to face the sun as much for as many hours as possible with no shadows cast on the panels.
Clean the panels to remove any dust or other debris that can obstruct the sun from reaching the panels for maximum power output.
If you are looking to save money by investing in a 4 kW Solar system, keep in mind that the likely payback period for such a system can be as long as 7-10 years unless there are subsidies available.
If the budget is available and the use of clean renewable technologies such as solar is important to you then definitely consider the investment.
Should you decide to invest in one, you can expect to run various household appliances including lights, washing machines, microwaves, TVs, fridges, and others for a duration that depends on the battery bank capacity provided that you do not exceed the inverter capacity.