The home battery promises to save hundreds of euros on the electricity bill

Leena Raito it looks like a cell phone screen with the humps of the utility company’s app.

“This shows that the average market price in October was 8.7 cents. Our price has been only 5.1 cents, which means the consumption effect has been almost four cents,” explains Raito.

Such a large reduction in the price of used electricity in a year would mean a saving of 500 euros per year.

A 15 kilowatt-hour battery was installed in the home of the Raitos, who live in Espoo’s Souka, in mid-September. It charges electricity when electricity is cheap and discharges it for use when exchange electricity is expensive.

Consumption effect is not entirely due to the battery, as the retired couple schedules the use of electricity for cheap hours anyway. The electric car is charged and household appliances run whenever possible when electricity is cheap.

The price of electricity also does not always vary as much as in early October. Timing of consumption and storage saves more when the price of electricity varies a lot.

But the battery still works. Raito’s battery system was purchased from the telecom operator Elisa. According to Elisa’s calculation, the consumption effect should bring an average saving of around 17 euros per month.

“You certainly won’t get rich with this, and at this point it’s still too early to assess profitability anyway,” says Timo Raito.

I are not cheap. Elisa sells batteries with a ten-year installment contract. Raitot costs 49.99 euros per month for the battery, which means a total of 6,000 euros in ten years. In addition, the installation work cost 2,000 euros.

So the equation does not seem very attractive if the saving is only 17 euros per month.

Se however, is only part of the equation. Elisa, like other home battery sellers, connects home batteries to the electricity system’s so-called reserve market, which balances electricity consumption and production throughout the day.

The system using Elisa’s artificial intelligence controls the use of Raitoj’s battery and at the same time the house’s electrical system.

Elisa optimizes the charging and discharging of the home battery according to the exchange or spot electricity price. The benefit goes entirely to the customer.

In addition, the battery capacity is used in the reserve market according to market conditions, and the benefit obtained from this is shared between Elisa and the customer.

Reserve electricity is traded on the market maintained by the grid company Fingrid. There are many products and sometimes the prices are high.

Among other things, the batteries allow the electrical system to be adjusted very quickly, which is necessary, for example, in the event of a sudden failure of large power plants.

Part Elisa therefore accounts for the reserve market’s income to the battery owners. In the calculation presented to Raidoi, the market return has been calculated as no less than 35 euros per month.

Elisa’s battery business only Jukka-Pekka Salmenkai says that Elisa’s profit calculations have been made with “conservative” i.e. cautious assumptions, i.e. there is no exaggeration in the figures, according to him.

The more the price of electricity fluctuates, the more useful you get from the battery. For example, in 2022, when the price of electricity fluctuated wildly, according to him, the battery would have generated more both with the customer’s consumption flexibility and with the income from the reserve market.

There are no solar panels on the tracks, but according to Salmenkaida, the biggest benefit from batteries comes when they are combined with solar power. When you can use the electricity you produce yourself, you completely save electricity transmission fees.

According to Elisa’s calculation, by storing the income from the panels, an additional income of 15 euros per month would be obtained.

Starting point In Elisa’s system, the battery functions above all as the home’s energy storage.

On the market there are a whole bunch of companies selling home batteries. The business idea of ​​most other companies is to use home batteries with remote control in the reserve market. But otherwise the business models are very different. And the yield or price promises are sometimes really drastic.

Participating in the reserve market may promise significantly higher compensation than, for example, Elisa starts from in its contracts.

Doctor of research Juha Koskela He and his colleagues from the University of Tampere have gone through some profit calculations.

“It’s not an official investigation, but no matter how we calculated, in the end result we fell quite far short of those promises,” he says.

If it is difficult to assess the profitability of a home battery in the short term, and it is even more difficult in the long term.

In the electricity reserve market, prices depend on supply and demand, as in any market. As the number of batteries that offer flexibility increases, the returns decrease accordingly.

On the other hand, the amount of electricity production that varies according to the weather is still growing at a furious pace. In addition to wind power, a total of hundreds of megawatts of solar power is under construction and many times that amount is being prepared. That’s why the need for control power also increases.

The equation there are many other unknown factors involved, such as how electricity consumption develops.

In addition to home batteries, large corporate batteries are also entering the electricity system in any case. For example, the Helsinki energy company Helen builds electricity storage facilities in connection with the production of renewable electricity. Many other electricity producers do the same.

Already a year and a half ago, Elisakin harnessed the batteries of its base stations for the use of the reserve market. In them, it has a total of 150 megawatt hours of reserve power. It is equivalent to 10,000 Raitoin home batteries.

Stripes With a 15 kilowatt-hour battery, you can use a house heated by geothermal energy for a few hours.

The battery supplies power with a maximum power of 4.5 kilowatts. Although it is not enough for an electric stove alone, nor for charging an electric car. The charging of the car is excluded from the automation offered by Elisa. A car’s battery easily absorbs 40–50 kilowatt hours with one charge.

In the end, the most important thing in Raitai’s household is not whether the battery’s profitability is a few euros plus or minus. Timo Raito spent his working career at Nokia and he enjoys technical things even in retirement.

It is interesting for the couple to follow the operation of the battery system and fluctuations in the price of electricity.

“I, for my part, am such a penny-pincher. That’s why this is interesting”, says Leena Raito.