Electricity Storage: Is a Storage Device for the Solar Power System Worthwhile?

6.5.2021
  1. An investment in the future
  2. Solar power makes ecological and economic sense
  3. Why should you increase your own consumption?
  4. How does an electricity storage device work anyway?
  5. This is why a power or battery storage device makes sense
  6. Power storage with lead-acid or lithium-ion battery?
  7. Battery storage with lithium-ion battery
  8. How much does an electricity storage device cost?
  9. Don't just look at the price
  10. Get more out of your solar power

A solar power system produces electricity mainly at midday and in the afternoon. A power or battery storage device stores solar power that you do not use immediately and makes it available at a later time. For example, in the evening or in the morning when you and your family need more electricity.

An investment in the future

Electricity storage devices can be worthwhile and pay for themselves if all the general conditions are right. You save money especially if your energy provider charges a lot for its electricity but pays little for your solar power. This calculation could well work out: Experts expect energy prices to rise and feed-in tariffs to fall in the next few years. If this should happen, there is much to be said for consuming more self-produced solar power, i.e. increasing self-consumption. Then an electricity or battery storage device should be worthwhile.

Solar power makes ecological and economic sense

Solar energy protects resources and the environment. A solar system on the roof also pays off financially: you reduce your electricity costs by 30 percent in the long term, make yourself independent of electricity price increases, increase the value of your house, secure government subsidies and optimise your tax burden. How quickly the investment pays off depends on many factors, including your own consumption. With a high proportion of self-consumption, the investment usually pays for itself in 15 to 20 years with an average lifespan of 30 years.

The Solar System on the Roof Produces Electricity, the Battery Storage Stores It.
A battery storage device provides solar power when you need more electricity or the sun doesn't shine enough.

Why should you increase your own consumption?

Solar electricity costs less than electricity from the grid. That's why you should use as much cheap solar electricity as possible and as little expensive electricity from your energy supplier as possible. That way you can reduce your energy costs. You can increase your own consumption with an electric boiler, a charging station for electric vehicles, a heat pump or by changing your behaviour. For example, if you wash and dry your laundry in the afternoon because your solar system produces more electricity then than in the evening. But you can also increase your own consumption with a battery or electricity storage device.

How does an electricity storage device work anyway?

In principle, the electricity storage device works like a car battery. The alternator produces more energy than the car needs while driving, for example for the lights or the air conditioning. The battery stores excess energy so that you can start the car next time. The battery stores electricity that you neither need yourself (self-consumption) nor feed into the grid. You can use this electricity in the evening or at night - or if the sun doesn't shine or doesn't shine enough for days.

This is why a power or battery storage device makes sense

Most households consume the most energy in the morning and evening. However, solar systems produce the most electricity at midday, when only a few people are at home. That's why many photovoltaic systems only achieve 30 to 35 percent self-consumption without storage. With an intelligent storage solution, you optimise your consumption, store energy and use it when you need it: in the morning, in the evening or at night. You double the self-consumption share to plus/minus 70 percent and use the environmentally friendly electricity you produce yourself around the clock.

Houzy Advice

Good to know

With a degree of self-sufficiency of 70 to 80 percent, you only have to purchase and pay for expensive electricity from your energy supplier during long periods of bad weather.

Solar System

Is a Solar System Worthwhile?

With our solar calculator you can analyse the solar potential of your roof in just a few minutes. Including self-consumption simulation.
Calculate Solar Potential Now

Power storage with lead-acid or lithium-ion battery?

If you are interested in a power storage unit, you basically have the choice between lead-acid or lithium batteries:

  • Lead batteries can be discharged and charged less often. The limit is plus/minus 3000 charging cycles. In addition, the efficiency of a solar system with a lead-acid battery is lower and the lead-acid battery can be discharged less deeply. Therefore, you can use less storage capacity for the same storage capacity. On the other hand, electricity storage systems with a lead-acid battery are significantly cheaper than lithium-ion batteries.
  • Lithium-ion batteries can be discharged and charged up to 7000 times, i.e. more than twice as often. The efficiency of a solar system with a lithium-ion battery is higher (up to 95 instead of only up to 86 percent) and lithium-ion batteries can be discharged more deeply (almost up to 100 instead of only up to 80 percent). On the other hand, battery storage with lithium-ion batteries is more expensive than lead batteries. Nevertheless, they are the most popular.

Houzy Advice

Good to know

The higher the number of charging cycles, the longer the service life. Lithium-ion batteries perform 4000 to 7000 charging cycles under full load. For a single-family house, you have to reckon with 250 to 300 cycles per year. This is how the service life of 15 to 25 years is calculated.

Houzy Hint

Tip

Do not calculate too short term. A lithium-ion battery may cost more, but it lasts longer and is more powerful. The high initial investment pays off over time. Especially if prices continue to fall thanks to increasing production.

Battery storage with lithium-ion battery

Lithium-ion batteries are not only longer-lasting and more powerful, but also significantly lighter. That is why they have long been installed in smartphones, tablets and electric vehicles. No wonder the currently most popular power storage device, the Tesla Powerwall 2, is produced by an electric vehicle manufacturer. Other well-known manufacturers of lithium-ion batteries include Fronius, sonnen and Varta. Their storage solutions can be easily mounted inside or outside on a wall, usually in the basement, and connected to the solar system on the roof.

How much does an electricity storage device cost?

The price depends on many factors. For example, the storage solution (lead-acid or lithium-ion battery), the number of charging cycles, the storage capacity, the depth of discharge and the power loss. For an average single-family home, calculate an initial investment of 6,000 to 12,000 Swiss francs for materials and installation. Our solar calculator assumes 10,000 francs.

  • If you already have a photovoltaic system installed on the roof, you can only retrofit an AC-coupled system. It converts the direct current of the solar system into alternating current for the household using two battery inverters. An AC coupled system is cheaper than a DC coupled system and easy to install, but not as energy efficient.
  • If you are only planning to install a photovoltaic system, you should opt for a DC-coupled system. On the one hand, all components are perfectly matched and the compatibility problem is solved; on the other hand, the system only needs one inverter. That is why it is more compactly built and significantly more energy-efficient than an AC-coupled system.

Houzy Advice

Good to know

In principle, you can retrofit almost any solar system with a battery storage device. How useful this is depends on the age of the photovoltaic system and the cost-benefit ratio of the storage solution. The performance of older systems decreases over the years.

Houzy Hint

Tip

The storage capacity should be based on consumption. The largest battery is of no use if you produce too little electricity in winter to fill the storage and consume too little electricity in summer to empty it.

Battery Storage: Expert Advice
Talk to a professional before choosing a storage solution

Don't just look at the price

When choosing a power storage device, don't just look at the purchase price. First compare the storage capacity, depth of discharge, number of charging cycles, available peak power and power loss. An expensive battery storage unit may well cost less per kilowatt hour (kWh) than a cheaper storage unit because it is more efficient and has a longer service life. Also consider the installation costs for the storage solution (or your time for installation) and the maintenance costs. Good advice is cheaper than a supposed bargain from the Internet. So it's better to ask an expert.

Houzy Advice

Good to know

The Energy Strategy 2050 also promotes electricity storage systems. The first two cantons to provide financial support for storage solutions are Schaffhausen and Thurgau. Ask your solar system provider or inform yourself online on how it looks in your canton.

Houzy Hint

Tip

Battery storage is particularly worthwhile in regions with low feed-in tariffs. When analysing the solar potential, our solar calculator also takes into account the regionally varying feed-in tariffs and simulates their effects on the profitability of electricity storage.

Get more out of your solar power

Get more out of your photovoltaic system with an electricity or battery storage system:

  • You cover 70 to 80 percent of your consumption with climate-friendly solar power (ecology).
  • You make yourself independent of your supply and rising energy prices (self-sufficiency).
  • You use more cheaper solar electricity and reduce your energy costs by 30 percent.
  • You can sustainably increase the value of your home with a solar system and an electricity storage device.

With the Houzy solar calculator, you can analyse the solar potential of your house roof, calculate the economic efficiency of a solar system and simulate various self-consumption scenarios with or without battery storage. The analysis tells you whether an electricity storage system is worthwhile for you or not.

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