How do I connect to CheckWatt's services?
The process begins by placing an order through one of CheckWatt’s partner companies.
The installation then proceeds as follows:
For larger, commercial battery systems, an individual prequalification with the transmission system operator – for example Fingrid in Finland, Svenska kraftnät in Sweden and Energinet in Denmark – may be required for the system to begin generating revenue for its full capacity. Consult your installer for specific requirements in your case.
What is the advantage of CheckWatt compared to the built-in functionality in my battery system?
When you buy a battery — whether it’s connected to CheckWatt or not — it often comes with built-in functionality that optimizes the usage of the battery based on the electricity consumption in your property. For example, the battery can automatically store surplus solar electricity for later use. For customers with hourly electricity pricing and dynamic grid tariffs, there is sometimes also an option to configure the battery to optimize usage based on electricity prices and reduce the property’s power peaks.
When you connect your battery to CheckWatt, you gain the ability to combine services that lower your electricity costs with selling ancillary services, providing local flexibility, and participating in various electricity markets. In order words, instead of providing three services for optimizing local energy usage with the built-in functionality of your inverter – you are, in addition, able to provide a wider range of more value-creating services. This significantly increases the potential earnings from your battery.
The services you can provide through CheckWatt also contribute more directly to the power system: ancillary services that maintain balance in the operation of the power system, local flexibility that in a precise way helps grid operators during the most strained hours, and trading on different electricity markets. These services contribute to a more stable power system, they reduce the need for costly grid expansions, and contribute to the continued build out of cheap, renewable electricity. Historically, these services have been — and continue to be — significantly more lucrative than the services provided by a standard battery system.
Which batteries and inverters are compatible with CheckWatt’s services?
CheckWatt’s services are compatible with most common brands of inverters and batteries on the market. Due to market specific rules and pre-qualification processes with national grid operators, the compatibility is different in different countries.
Here you can see if your inverter is compatible with CheckWatt services in Sweden and Finland, our largest markets. These lists are continuously updated as new brands are added.
Which electricity retailers are compatible with CheckWatt’s services?
In countries such as Finland and Denmark, CheckWatt can register as a direct supplier of grid balancing services to the transmission system operator — Fingrid in Finland or Energinet in Denmark. This means we can deliver our services, regardless of the electricity supplier of the customer.
In a market such as Sweden’s, CheckWatt needs to partner up with the customers’ electricity retailers and their respective balance responsible party in order to deliver services. Each electricity retailer has a so-called balance responsible party, which is financially responsible for ensuring that there is a balance between the electricity bought and sold, and the electricity consumed and produced. These balance responsible parties are also the ones who submit bids for grid balancing services. CheckWatt’s services are compatible with a large share of Sweden’s electricity retailers. You can see if an electricity retailer is compatible in this list.
If you live in Sweden and your electricity retailer is not on the list, you will need to switch to one that is in order to use CheckWatt’s services.
What is a virtual power plant?
A battery is versatile. It can be used in the home or building to reduce electricity costs by shifting consumption to low-price hours, increasing solar self-consumption, or reducing grid costs.
If a battery, together with other batteries (and other flexible resources), is connected to a ‘virtual power plant’, it can also provide services to various actors in the electricity system. Examples include ancillary services to the transmission system operator — such as Fingrid in Finland, Energinet in Denmark or Svenska kraftnät in Sweden — and flexibility to local grid operators during times when the grid is constrained. These services often have requirements regarding minimum bid size, geographic location, and technical performance.
A company like CheckWatt — known as an ‘aggregator’ — enables these resources to collectively meet those requirements and manages all the administration related to this type of service.
Connecting to a virtual power plant means the revenue potential is significantly higher compared to when the battery is only used based on the building’s own needs.
What is CheckWatt’s binding contract period?
For residential systems, we have no binding contract period. It may however take up to a week from the time you notify us that you wish to terminate the service until it is fully deactivated.
What happens if I move and someone else takes over the battery system?
Contact the CheckWatt partner responsible for supporting your system, and they will help you transfer the system to the new owner.
What happens if the company responsible for supporting my system goes bankrupt?
If one of CheckWatt’s service partners goes bankrupt or if the partnership ends for any reason, CheckWatt will take responsibility for finding a new service partner to take over the support of your system. In that case, we will contact you by email.
CheckWatt offers two operating modes: Currently Optimized (CO) and Self Consumption (SC).
CO is our recommended operating mode and is designed to optimize battery control in order to maximize profitability at any given time. Systems using this mode combine the delivery of various ancillary services with value creation locally in the property — such as storing self-produced solar energy and electricity price arbitrage (i.e. charging the battery when prices are low and discharging when prices are high). Customers that live in an area with a local flexibility market also provide local flexibility during winter when the grid is most strained.
The benefit of this mode comes from both direct revenue from providing ancillary services and local flexibility, as well as cost savings on electricity.
SC is our operating mode where the battery is used solely to increase self-consumption of solar energy and — if the customer has an hourly pricing agreement — for electricity price arbitrage. The benefit of this mode comes only from cost savings on electricity, with no direct income. Overall, the profitability of this mode is significantly lower than that of CO.
Read more about our recommended operating mode CO via this link.
When you choose CheckWatt’s recommended operating mode, Currently Optimized (CO), the battery is controlled in order to deliver services to various electricity system actors (such as ancillary services) while also performing tasks locally in the property to reduce your electricity costs.
In order to lower your electricity costs, we need to forecast your electricity consumption and production, while also taking into account electricity prices and the tariffs and contracts you have with your grid owner and electricity retailer. We call this system CheckWatt AI.
CheckWatt AI is an integrated part of our Currently Optimized operating mode. The optimization varies based on the conditions at your property — for example, whether a solar PV system is installed. Electricity price arbitrage — meaning charging during low-price hours and discharging during high-price hours — is only performed for customers who have indicated in our customer portal, EnergyInBalance, that they have an hourly pricing agreement.
As CheckWatt AI runs in parallel with the delivery of ancillary services, the charge level and the power used locally in the property are limited in order to deliver ancillary services reliably. For typical residential systems, around 20–45 percent of the battery’s energy capacity is used for storing solar energy and electricity price arbitrage. Charging and discharging power is also typically limited to around 1–2 kW. You can read more about the details on CheckWatt AI here.
To ensure balance in the power system, the national transmission system operators (TSOs) — such as Fingrid in Finland, Energinet in Denmark and Svenska kraftnät in Sweden — procure several ancillary services. They are all used as tools to maintain the grid frequency as close to 50 Hz as possible.
We list all ancillary services and their respective characteristics below. They are listed in order based on how fast they respond.
The purpose of FFR — the fastest ancillary service — is to slow down rapid frequency drops when there is little inertia in the power system, such as when electricity consumption is low and wind or solar power makes up a large share of production. In the Nordic power system the need for FFR is largest during summer months when maintenance is carried out on hydro and nuclear power plants. FFR is generally the ancillary service with the lowest demand.
Activating FFR means the batteries are discharged very quickly. Providing FFR requires an extra electricity meter, which usually isn’t cost-effective for smaller battery systems such as in households.
A fast ancillary service that responds to frequency disturbances in the grid. When delivering FCR-D, you receive compensation for having capacity available, either by charging or discharging the battery. The compensation is proportional to the system’s power rating, which is limited by a combination of the inverter’s and battery’s output as well as the grid connection. For example, a 100 kW system earns ten times more than a 10 kW system.
Typically, batteries delivering FCR-D operate at a state of charge between 30–70% to allow for rapid charging or discharging, depending on whether the frequency is above 50.1 Hz or below 49.9 Hz. The largest and most prolonged frequency deviations usually occur due to sudden stops in nuclear power plants or large sub-sea transmission cables. In general, there is relatively little charge and discharge for a battery delivering FCR-D.
FCR-N is similarly to FCR-D an ancillary service where batteries are paid for capacity, i.e. they are remunerated for standing ready to charge or discharge. In addition to capacity payments, batteries delivering FCR-N are compensated for the actual energy they deliver. FCR-N is activated proportionally to frequency deviations within the range of 50 Hz ± 0.1 Hz. Since the frequency often slightly deviates from 50 Hz, batteries providing FCR-N charge and discharge much more frequently than those providing FCR-D.
FCR-N has endurance requirements of one hour, as opposed to twenty minutes for FCR-D. In practice, this means that batteries with a higher energy-to-power ratio earn more from supplying FCR-N; for example, a 10 kW/20 kWh battery compared to a 10 kW/10 kWh battery earns around 60% more. FCR-N is a much smaller market than FCR-D because the need for the service is smaller.
mFRR is an energy-intensive ancillary service intended to handle imbalances caused by forecasting errors between electricity consumption and production — an issue that becomes more common as the share of renewable and harder-to-predict generation increases. Batteries delivering mFRR can receive both a capacity payment for being ready to deliver and payment for actual energy delivered on the energy activation market.
Unlike FCR-D and FCR-N, which are automatically triggered based on measured frequency deviations, mFRR is activated manually via a signal from the transmission system operator (TSO) through the balance responsible party. This means that delivering mFRR requires technical integration between the TSO, the customer’s balance responsible party, and CheckWatt.
mFRR is the ancillary service with the largest market in megawatts. When activated on the energy market, batteries either charge or discharge continuously for a 15-minute interval.
aFRR, like mFRR, is intended to restore the grid frequency to 50 Hz. As the name suggests, aFRR is activated automatically, whereas mFRR is activated manually. Unlike the other ancillary services, CheckWatt is not currently delivering aFRR. In Sweden this has partly been due to technical and administrative barriers preventing third-party companies like CheckWatt from offering aFRR. However, this was changed on January 15, 2025.
Currently, the demand for aFRR is lower than for mFRR, FCR-D, and FCR-N.
CheckWatt delivers the ancillary services FFR, FCR-D, FCR-N, and mFRR. The only service we do not currently provide is aFRR.
Exactly which ancillary services a specific battery can deliver depends on the market, the technical regulations, and partly on how CheckWatt prioritizes which services batteries are prequalified for. For example, FFR requires a relatively expensive electricity meter, which makes delivering FFR economically unviable for residential systems. In Sweden, we have prioritized prequalifying residential systems for FCR-D and mFRR because these markets are relatively large and prices have been high. During the summer of 2025, we are also starting to prequalify residential systems for FCR-N.
In Finland and Denmark, we have initially started to deliver the ancillary services FCR-D and FCR-N. We are continuously working on adding more ancillary services in these markets.
For batteries to be able to deliver ancillary services, a series of tests must be performed to prove they meet certain technical requirements. The test results are then submitted to the national transmission system operator for approval. In total, this process can take anywhere from a few weeks to several months. The specific test depends on the service, but a typical test takes a couple of hours.
For some ancillary services, CheckWatt is allowed to perform type qualification. This means that batteries with similar characteristics to those we’ve already prequalified can be added to an existing approval without the need for new tests. This type qualification is what allows us to begin delivering FCR-D and FCR-N from a newly connected residential system from day one.
A similar kind of prequalification may also be required for other services, such as local flexibility for grid operators, though this is generally a much simpler process.
Battery owners can, through CheckWatt, sell services to local grid owners to help manage periods when the electricity grid is constrained. This typically occurs during the coldest winter days, but challenges can also arise in summer when solar production is high and electricity consumption is low. Purchasing flexibility from batteries is a cost-effective alternative to investing in new grids, while also enabling more customers and industries to faster connect to the grid.
Today, around 10 percent of CheckWatt’s Swedish customers live in areas where the local grid operator buys flexibility during the colder months of the year. In Finland, a first local flexibility market is being launched by Fingrid and the Helsinki-based grid owner Helen. Activations on local flexibility markets typically occur during a few hours of the year, but are often well compensated. For example, in the winter of 2024/2025, around 500 CheckWatt customers in Gothenburg and Mölndal in Western Sweden participated in the local flexibility market Effekthandel Väst, generating additional revenue beyond what was earned from ancillary services and local battery optimization.
Driven by EU legislation, it’s likely that all grid operators will be required within a few years to purchase flexibility as a way to avoid unnecessarily expensive grid expansion. You can read more about CheckWatts experiences delivering local flexibility through this link.
No, once your battery is connected to CheckWatt, we take over control of the system. We collect data and handle forecasting and optimization of charging and discharging, while also managing all administration with the transmission system operator and other stakeholders. However, to optimize the usage of the battery, we ask our customers to fill in certain information in our customer portal, EnergyInBalance — for example, whether they have an hourly pricing agreement or not.
More and more grid operators have started introducing dynamic grid pricing, where part of the monthly cost paid to the grid company is based on the hours of highest electricity consumption during the month.
The savings that peak shaving can generate vary from case to case, depending on factors such as the structure of the tariff and the consumption profile of the property. For example, it’s common for grid companies to apply dynamic grid pricing only during the colder months of the year when grids are more constrained. Additionally, consumption peaks are harder to predict compared to other aspects such as ancillary services, electricity prices or self-consumption of solar electricity — where the customer receives compensation more or less immediately after the service is delivered. With most dynamic grid pricing, just a few instances in a month where the battery fails to do peak shaving can significantly reduce or eliminate the potential savings.
During the summer and fall of 2025, we are conducting a pilot project with the aim of implementing peak power creation in our governance.
In your account in our customer portal, EnergyInBalance, under the ‘Dashboard’ page, you can view the status of your system. If the status indicator is green and says ‘Activated’, it means everything is working as it should. If the status indicator is yellow, it means the system is currently being tested for delivery of ancillary services. If the system has not been activated after three days, the status will turn red.
If the status indicator is red, you should contact the CheckWatt partner responsible for operating your system for further troubleshooting.
CheckWatt always performs automatic actions when the system status changes from green to yellow, such as restarting the system software and updating the software version. If it’s cold — or if other factors affect the battery’s performance — we also have automated systems that adjust the system’s power output so it can continue delivering services even when performance is reduced. You can read more about the tests we perform via this link.
CheckWatt charges a monthly fee of €5 per system, excluding VAT. This monthly fee is deducted from the payment made at the end of each month.
CheckWatt and the company responsible for operating the customer’s system also charge a performance fee at 20 percent of the total compensation the system has generated (this fee is split 10 percent to CheckWatt and 10 percent to the company responsible for support). When a customer views their earnings in our customer portal EnergyInBalance, these performance based fees have already been deducted.
Since the prices of electricity and ancillary services are set on open markets, revenues will vary from month to month and over time. If you live in Sweden, you can view historical compensation data on this page. We are working on a similar page for Finnish customers.
By connecting your battery to CheckWatt, you gain access to more markets and services than if you only use the battery’s built-in control system. We also manage the optimization aimed at maximizing your battery’s profitability.
As the owner of the battery, you receive the majority of the compensation, but 20 percent of the generated value is shared between CheckWatt and the company responsible for supporting your system. CheckWatt also charges a monthly fee of €5 (excluding VAT).
Generated revenue varies from month to month depending on market prices. Additionally, following factors influence the revenue and savings that your battery generates:
Compensation is reported in EnergyInBalance either on a daily or monthly basis. For Swedish customers, this depends on the electricity retailer and you can see in this document whether data is reported daily or monthly. In Finland, compensation is updated daily for all customers.
Once a system has been commissioned, the first payment is usually made 60 days after the end of the month and is paid either directly from us or via the customer’s installer. The delay is mainly due to the time it takes for CheckWatt to receive the payment for the delivery of ancillary services from the transmission system operator — Svenska kraftnät in Sweden and Fingrid in Finland — and the balance responsible party. Approximately 30 days after the end of the month, a so-called self-invoice is sent out informing each customer of the determined compensation. At this time, the compensation graphs in EnergyInBalance (which until then have been preliminary) may also be corrected slightly.
Once the system has been in operation for two months, compensation is then paid at the end of each month.
CheckWatt is a company that manages energy resources in a smart way. All installations of CheckWatt are done through our experienced partner companies. Find and installer near you or read more about our services.
Together, we’re making the power system smarter and more renewable.
