How Much does Home Solar Battery Cost Per kWh?

What is the cost of home solar battery per kWh? Do you even need a residential battery backup for your photovoltaic system? Here you will find the answers.

The cost of home solar battery use varies widely, depending largely on the solar battery company. In the past, we used lead-acid batteries to store solar energy. While the technology for lead-acid batteries is relatively mature, the expected cost per kilowatt hour can be $500 to $1,000!

Lithium-ion solar batteries are gradually replacing lead-acid batteries as the next generation of home battery backup systems because of their higher efficiency, more available capacity and longer service life, but they also come with a higher purchase cost, so the expected cost per kWh for lithium-ion home solar batteries is $800 to $1,350.

Are home solar batteries worth it?

Photovoltaics generates electricity from sunlight. Accordingly, a photovoltaic system can only generate a lot of energy when the sun is shining. This applies especially to the time from morning to afternoon. In addition, you have the greatest electricity yield in spring, summer and fall. Unfortunately, these are also the times when your household needs comparatively little electricity. Electricity consumption is highest in the evening hours and during the dark winter months. So, in summary, this means:

  ● The system delivers too little electricity just when you need it.

  ● On the other hand, too much electricity is produced during the time with the lowest demand.

Therefore, the legislator has created the possibility to feed solar power that you do not need into the public grid. You receive a feed-in tariff for this. However, you must then purchase your electricity from the public energy suppliers at times of higher demand. The ideal solution to be able to effectively use the electricity yourself is a battery backup system for your photovoltaic system. This allows you to temporarily store excess electricity until you need it.

Do I necessarily need an home solar battery system for my photovoltaic system?

No, photovoltaics also works without battery storage. However, in this case you will lose the surplus electricity in high-yield hours for your own consumption. In addition, you have to purchase electricity from the public grid at times of highest demand. You get paid for the electricity you feed into the grid, but you then spend the money on your purchases. You may even pay more for it than you earn by feeding it into the grid.

In addition, your income from the feed-in tariff is based on legal regulations, which can change or be completely canceled at any time. In addition, the feed-in tariff is only paid for a period of 20 years. After that, you have to sell your electricity yourself through brokers. The market price for solar power is currently only about 3 cents per kilowatt hour.

Therefore, you should strive to use as much of your solar power as possible yourself and therefore buy as little as possible. You can only achieve this with a home battery storage system that matches your photovoltaics and your electricity needs.

What does the kWh figure mean in relation to home solar battery storage?

The kilowatt hour (kWh) is a unit of measurement of electrical work. It indicates how much energy an electrical device generates (generator) or consumes (electrical consumer) during one hour. Imagine a light bulb with the power of 100 watts (W) burns for 10 hours. Then this results in:

100 W * 10 h = 1000 Wh or 1 kWh.

For home battery storage systems, this figure tells you how much electrical energy you can store. If such a home battery storage system is specified as 1 kilowatt hour, you can use the stored energy to keep the above-mentioned 100-watt light bulb burning for a full 10 hours. But the premise is that the home solar battery storage must be fully charged!

When is a battery backup system for home worthwhile?

As studies have shown, you can only use 30 % of the electricity generated by your photovoltaic system yourself. With the use of a solar home battery bank, this value increases to 70% - 80 %. To be profitable, the kilowatt hour from your solar home battery storage must not be more expensive than the kilowatt hour purchased from the public grid.

Photovoltaic system without solar home battery bank

To determine the amortization of a photovoltaic system without solar home battery bank, we use the following example values:

  ●  Cost of solar modules with 5 kilowatt peak (kWp) output: 7500 dollars.

  ●  Additional costs (for example connection of the system): 800 dollars.

  ●  Total costs for the purchase: 8300 dollars

Solar modules with a total output of 1 kilowatt peak generate approximately 950 kilowatt hours per year. Thus, the total yield for the system is 5 kilowatt peak (5 * 950 kWh = 4,750 kWh per year). This is roughly equivalent to the annual electricity needs of a family of 4.

As already stated, you can only consume about 30 % or 1,425 kilowatt hours yourself. You don't have to buy this amount of electricity from the public utility. At a price of 30 cents per kilowatt hour, you save 427.5 dollars in annual electricity costs (1,425 * 0.3).

On top of that, you earn 3,325 kilowatt-hours by feeding electricity into the grid (4,750 - 1,425). The feed-in tariff currently decreases monthly by a percentage of 0.4 percent. For the subsidy period of 20 years, the feed-in tariff for the month in which the plant was registered and commissioned applies. At the beginning of 2021, the feed-in tariff was around 9 cents per kilowatt-hour.

This means that the feed-in tariff results in a profit of 299.25 dollars (3,325 kWh * 0.09 euros).

The total saving in electricity costs is therefore 726.75 dollars. Thus, the investment in the plant would pay for itself within about 11 years. However, this does not take into account the annual maintenance costs for the system of approx. 108.53 euros.

Photovoltaic system with home solar battery storage

We assume the same plant data as mentioned in the previous point. A rule of thumb says that the lithium ion solar battery bank should have the same storage capacity as the power of the photovoltaic system. Thus, our system with 5 kilowatts peak includes a home solar battery backup with a capacity of 5 kilowatts peak. According to the average price of 800 dollars per kilowatt-hour of storage capacity mentioned above, the storage unit costs 4000 dollars. The price for the plant thus increases to a total of 12300 dollars (8300 + 4000).

In our example, as already mentioned, the plant generates 4,750 kilowatt-hours per year. However, with the help of the storage tank, the self-consumption increases to 80 % of the generated electricity quantity or 3800 kilowatt-hours (4,750 * 0.8). Since you don't have to buy this amount of electricity from the public utility, you now save 1140 dollars in electricity costs at an electricity price of 30 cents (3800 * 0.3).

By feeding the remaining 950 kilowatt-hours (4,750 - 3800 kWh) into the grid, you earn an additional 85.5 dollars per year (950 * 0.09) with the aforementioned feed-in tariff of 8 cents. This results in a total annual saving in electricity costs of 1225.5 dollars. The plant and the storage system would pay for themselves within about 10 to 11 years. Again, we have not taken into account the annual maintenance costs.

What should I pay attention to when buying and using home solar batteries?

Due to better efficiency and a longer lifetime than lead batteries, you should buy a home battery storage with lithium-ion batteries. Make sure that the home solar battery can withstand about 6,000 charging cycles and get offers from several suppliers. There are also considerable price differences for modern battery storage systems.

You should also install the home solar battery bank in a cool place inside the house. Ambient temperatures above 30 degrees Celsius should be avoided. The devices are not suitable for installation outside the building. You should also discharge the lithium ion solar batteries regularly. If they remain under full charge for a long time, this will have a negative effect on their lifespan.

If you follow these instructions, the home solar battery bank will last much longer than the 10-year warranty period usually given by manufacturers. With the right usage, 15 years and more are realistic.