What is your solar surplus worth at noon? Self-consume, store, share or inject

The same kWh, four possible values

When the panels produce more than the house consumes, the surplus from midday can follow several paths. It can be used immediately for hot water, vehicle or appliance charging. It can charge a battery and come back in the evening. It can be sold to a neighbor in a local consumption model, if network conditions and participants permit. It can finally be injected into the network according to the network manager's price.

Not all of these options add up. A kWh consumed directly cannot be stored or sold at the same time. The comparison must therefore start from the same kWh and remove losses, costs, availability of equipment and household constraints. The answer that promises “always more value with a battery” does not do this calculation.

The value of the surplus is local. The purchased tariff, injection tariff, measurement cost, bundling model and future prices change depending on the DSO and the project. ElCom publishes a national median, but it does not replace the bill for your address. Swissolar also describes a new remuneration model more linked to the market from 2027, which makes the hourly form of production more important.

To decide, start with a charging curve and not the size of a battery. Measure when the house consumes, when it is empty, which appliances can be moved and how much surplus actually appears. Only then compare storage, sharing and injection.

The priority: direct consumption

The kWh consumed directly is often the easiest to value. It avoids a purchase at the price of your household electricity, which includes energy, network, metering and other components. It does not require a second conversion and does not depend on an injection rate. This comparison remains to be made with the actual GRD prices.

Direct consumption does not mean that you have to change the whole life of the house. Some loads are flexible: water heater, dishwasher, washing machine, swimming pool pump, ventilation, air conditioning or vehicle charging. A simple order can move these devices into production. Comfort, hygiene and vehicle departure times remain priorities.

The presence of a device does not guarantee consumption of the surplus. A terminal may require a minimum power greater than the available surplus. A water heater may already be hot. A heat pump can be stopped by its regulation. The simulation must therefore model real operation, not just count a device in a list.

A control system can use measurement at the connection point, an inverter output or smart meter information. Ask what data triggers the device, how often it is updated, how the system responds to clouds and whether the setting remains accessible to the owner. Control dependent on a subscription or an Internet connection must be identified in the cost and risk.

The surplus that charges a battery

A battery transforms part of the midday energy into electricity available in the evening. Its value comes from the difference between the price of a kWh purchased in the evening and the value of the kWh that would have been injected at midday, after losses and costs. You also need to consider the cost of the battery, its useful capacity, charging power, warranty, age and possible replacement of the inverter.

The calculation should start with evening consumption. If the house uses 4 kWh between 18 h and 23 h, a battery with a usable capacity of 10 kWh will not create 10 kWh of value every day. It will sometimes be partly charged, sometimes full before the peak and sometimes reserved for backup mode. The model must display the kWh actually charged, returned and lost.

The battery can also help with an injection limit. It reduces export during certain peaks if its capacity and power are available. But a full battery cannot absorb new production. Very high production days may be few in number; the battery should be sized on the frequency and value of events, not on exceptional photography.

Swissolar reports strong growth in battery installations in 2026 and a drop in the indicative cost of certain domestic systems. This development is important, but the purchase price is only part of the calculation. Operation, replacement, warranty, security, data and rescue mode should be included. A less expensive but difficult to control system may have a lower value.

The surplus shared locally

A group of own consumption, a virtual RCP or a local electricity community can allow a midday kWh to be consumed by another nearby building. The producer can get better value than traditional injection, while the consumer can pay less than their full network tariff. The difference depends on the network costs avoided or maintained, taxes, meter and contract.

Swissolar presents RCPs, virtual RCPs and local electricity communities as models that can bring production and consumption closer together. They are particularly interesting for a PPE, several houses or a small neighborhood. They are not a simple application to activate. It is necessary to check the network perimeter, the meters, the role of the DSO, the billing rules and the duration of commitment.

Sharing changes the risk profile. A neighbor can move, consume less or install their own battery. A community must know who finances the meter, who bills, who manages outstanding payments and how a member exits the model. The local price of a kWh must be set with an understandable formula, not just with a promise of reduction.

In a building, also analyze the distribution between owners, tenants and common areas. The elevator, ventilation, laundry room and heat pump can be stable local consumers. Their measure and contract must be identified. A system that excludes common consumption may underestimate the value of the surplus.

The surplus injected into the network

Injection is the simplest solution technically: the network absorbs the surplus and the DNO applies its recovery tariff. It may be the best option when the house has almost no flexible consumption, the battery price is high or the sharing project is too complex. However, it must be calculated with the actual price and its validity period.

Do not confuse the purchase price of your electricity with the purchase price of your surplus. The first avoids a full cost for the energy consumed; the second pays for exported energy according to a separate rule. ElCom points out that prices are published and set by supplier, with network and measurement components. Your invoice and the conditions of the GRD are the reference.

Swissolar describes a model for 2027 in which the remuneration for injected solar energy is more linked to the hourly market price, with minimal protection for certain small installations. The transition can change the value of a midday kWh, especially if prices are low when a lot of solar is produced. You should avoid promising a 2027 rate identical to today's rate: ask for the conditions applicable to your DSO.

Injection also has the value of simplicity. A battery-free system has fewer components, less losses and less maintenance. If the economic difference with storage is small, the owner may prefer the solution that is easier to understand and replace. Profitability should not be separated from operational risk.

A comparison method in six lines

Take one kWh produced at noon and write four paths. In the first, it is consumed directly. In the second, it charges a battery and then is used later. In the third, it is consumed by a local participant. In the fourth, it is injected into the GRD. For each path, note the gross value, losses, costs, equipment needed, and the probability that the path will be available.

For direct consumption, use the rate you are avoiding and a presence hypothesis. For the battery, remove the charge and discharge efficiency, then allocate the system cost over the kWh actually moved. For local sharing, add the cost of metering, administration and the risk of a member leaving. For injection, use the GRD price, its formula and its known evolution.

The result can be presented as an annual low, middle and high value. The low scenario must survive a drop in consumption during the day, a less used battery or low injection remuneration. The high scenario can include a terminal available at lunchtime, but it must remain clearly labeled as a hypothesis.

A calculation over twenty years must also include the replacement of the inverter, insurance, possible cleaning, maintenance, price indexation and the cost of capital. Don’t mix purchasing assistance with recurring income. A grant reduces the initial cost; it does not guarantee the future value of kWh.

What choice for which profiles?

Family presents part of the day

Start with piloting and hot water. A small battery can complete evening uses, but it should not replace simple programming. The electrical terminal is interesting if the car is actually at home during sunlight hours.

Empty house during the week

Battery or local sharing can increase the value of the surplus. Compare storage size to evening consumption. If the car returns after production, do not attribute to it self-consumption that does not exist.

PPE with several accommodations

Local sharing can be powerful because profiles complement each other. Common consumption, metering, billing and exit rules are as important as the panels. Ask for a simulation per building and not an average for the building.

Secondary residence

Injection may be simpler than a large battery. A reliable surveillance system and security are priorities. The calculation must consider the low presence and costs of remote control.

Mistakes to avoid

The first mistake is to measure the surplus only in summer. A battery may be full during sunny days and unused in winter. The second is to give local sharing a full retail price excluding network, taxes and administration. The third is to compare a new battery to an injection whose price has not been verified.

The fourth mistake is forgetting the measuring point. A system can control a device from raw production while the house already consumes part of the energy. This hardly increases self-consumption. A measurement at the connection point actually shows the export.

The fifth is to confuse independence and profitability. A battery can provide a useful backup mode, but this service has a specific value. It should not be sold as a financial gain on each kWh. Ask which loads stay powered, for how long, and whether the system works during an internet outage.

Questions to ask before choosing

A reliable offer responds with a curve and kWh. An offer that only shows the battery capacity or the maximum buy-back price does not allow a comparison.

Shopping checklist

First gather the invoices, load profile, attendance periods, flexible devices and local rate. Then request an hourly or quarter-hour simulation without additional equipment. This result becomes the basis for comparing control, battery, sharing and injection.

For each variation, ask for initial cost, maintenance, losses, revenue and savings. Note contractual commitments and data responsibility. If a local model is offered, read the exit conditions and transfer price. If a battery is offered, request an offer without battery and an offer with battery.

Finally, have the connection and measurement checked. A good simulation can become false if the inverter is limited, if the meter does not measure the expected flow or if a DSO changes the tariff. The value of a surplus is based on a system actually connected and measured.

A numerical example without false precision

Let's imagine that a house has a surplus of 2 000 kWh per year after direct consumption. In the first variant, all this energy is injected. In the second, additional control consumes 400 kWh directly. In the third, a battery returns 700 kWh in the evening after having absorbed more at midday. In the fourth, a neighbor uses 600 kWh via a local model and the balance is injected. These numbers are not a prediction; they show why the paths must be separated.

Direct management generally avoids conversion losses and significant investment. The battery only values ​​the 700 kWh actually returned, less its implicit annual cost and the risk of replacement. Local sharing can give a better gross value to the 600 kWh, but you have to pay for metering, administration and management of departures. The injection remains the residual output and must be calculated with the DSO tariff.

If the avoided purchase price is 25 cents, the local take-back rate is 10 cents and the sharing value is 18 cents, the three kWh are not equivalent. A kWh used directly has a different value from a kWh stored and then returned, even if both come from the same peak. In the decision, replace these illustrative values ​​with your written rates and add losses. Apparent precision only makes sense if the assumptions are traceable.

This example also shows that a device should not be credited with all the surplus. Control, battery and sharing compete for the same quantity of energy. A simulation that adds up the gains from all four options promises more value than the roof can produce.

So ask the service provider for a sheet where each kWh appears only once. This simple discipline makes the comparison more credible and allows you to modify a hypothesis without redoing the entire offer.

Access, contracts and future changes

The owner must be able to consult production, purchasing, export, storage, priorities and prices. If only the installation company can modify the battery, this dependency must appear in the contract. Download data out of the portal and request manual mode for urgent uses.

A future electric vehicle, heat pump or community can change the curve, but should not be credited as a certain saving before it is put into service. Request a current scenario and a future scenario, with date, cost and actual presence of the vehicle. Preparing the table and the measurement system may be more relevant than an immediate purchase.

During a change of owner, transmit statement, history, injection rate, commitments and definition of flows. The person taking over the house must know whether each kWh is directly consumed, stored, shared or injected.

Observe the seasons before buying

Track the surplus in spring, summer, fall and winter. In summer, a battery may be full before peak and local sharing may be more valuable. In winter, consumption sometimes increases while production decreases. A single sunny weekend does not allow storage to be dimensioned.

A terminal, boiler or heat pump must be present and available to absorb the surplus. Note actual schedules, minimum power, comfort and priorities. A control that starts and stops at each cloud may create less value than a simple schedule.

For sharing, control participants, counter, price and output. For injection, use the DSO price and its date. For the battery, count the kWh returned, not just the capacity. The four paths must be compared on the same curve.

The change in value over time

A new heat pump, a vehicle or an hourly rate can change the use of the surplus. Ask for a current scenario and a future scenario with date and cost. Swissolar describes a remuneration evolution from 2027; it must be verified with the DSO and does not justify a fixed promise.

The owner must maintain data, priorities, contracts and exports from the platform. A useful solution remains usable after changing person, router or supplier.

The owner must keep control

A battery, control or community must remain understandable without the installer. Request proprietary access, data export and manual mode. If a platform closes or the router changes, measurement, security and billing must continue.

When changing occupants, transmit load curve, prices, settings, guarantees and contracts. The new user must understand the priorities between direct, storage, sharing and injection. This continuity avoids assigning a fictitious value to the surplus simply because an old graph showed a high percentage.

Conclusion

The lunch surplus is neither free nor without value. It has four possible uses, and their order depends on your home. Start by consuming directly, then evaluate control, storage, local sharing and injection with the rates for your address. Battery is not the universal answer, and injection is not a failure.

The best strategy is one that remains understandable when prices, the presence of residents or the rules change. An honest load curve, complete costs and readable contracts will allow you to give each solar kWh the value that really corresponds to your situation.