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Article author:
Michael LiuArticle published at:
August 12, 2026Article comments count:
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A warm summer evening in Germany, the sun is low on the horizon, and a glance at the photovoltaic system or balcony power plant app shows pleasing figures: the modules are still delivering between 600 and 700 watts of power. But a look at the current household consumption quickly brings disillusionment. The base load from the refrigerator, router, and standby devices is only 100 to 150 watts.
This means: Every hour, over 500 watt-hours flow unused into the public power grid. For plug-in solar systems, there is generally no remuneration for this. But even for larger rooftop systems with feed-in tariffs, the remuneration is far below the price you have to pay for purchasing grid power (currently approx. 35 to 40 cents per kWh).
In this comprehensive guide, you will learn how to keep this evening energy surplus specifically within your own household, what priorities you should set for load shifting, and when investing in modern intermediate storage pays off.
The Basic Problem: Why is there so much surplus in the evening?
Modern photovoltaic modules are characterized by excellent low-light performance. Especially in the summer months of June to August, east-west or south-west oriented systems generate significant yields until approximately 8:30 PM.
At the same time, user behavior often does not change at the same pace in the evening:
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Residents relax on the terrace or in front of the TV.
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Large consumers like the washing machine already ran during the day or not at all.
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The stove is only used briefly, after which the household load quickly drops back to the base load.
Anyone who does not manage this electricity specifically wastes valuable energy. The solution lies in a well-thought-out combination of load shifting and accumulation.
Strategy 1: Intelligent Load Shifting in the Household
The most economically favorable method of utilizing solar power is direct consumption at the moment of generation. Since there are no conversion losses due to batteries, the efficiency here is almost 100 percent.
To precisely capture a surplus of 600 to 700 watts in the evening, a structured priority schedule for household appliances is recommended.
+-------------------------------------------------------+
| PRIORITY 1: HEAT & WATER |
| (Domestic hot water heat pump, heating element, kettle)|
+-------------------------------------------------------+
|
v
+-------------------------------------------------------+
| PRIORITY 2: HOUSEHOLD ELECTRONICS |
| (Dishwasher Eco Program, Washing Machine) |
+-------------------------------------------------------+
|
v
+-------------------------------------------------------+
| PRIORITY 3: BATTERIES & SMALL APPLIANCES |
| (E-bike, tools, robot vacuum cleaner, power banks) |
+-------------------------------------------------------+
Priority 1: Thermal Energy Storage (Hot Water)
Water has a high specific heat capacity and is ideal as a "thermal battery":
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Domestic Hot Water Heat Pump (DHWHP): A modern DHWHP often only requires between 300 and 500 watts of electrical power in operation. The 600–700 watt surplus fully covers this load.
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Electric Heating Element in the Buffer Tank: If you use a steplessly adjustable heating element, you can directly route the 600 watts into the hot water tank. This way, the main heating system remains completely switched off in the evening.
Priority 2: Household Electronics with Timer Function
Modern dishwashers and washing machines offer programmable start times or smart home connections (e.g., Home Connect):
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Dishwasher in Eco Mode: After heating up (where short-term high peaks occur), the continuous power of an Eco wash cycle is often only 150 to 300 watts. A surplus of 600 watts covers this process for 2 to 3 hours.
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Washing Machine (Cold or 30°C Wash): If you do a load of laundry in the evening, you deliberately utilize the heating phase within the solar window.
Priority 3: Batteries and Charging Processes
An underestimated lever is charging battery-powered everyday devices:
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E-bikes: Standard chargers for e-bikes draw between 150 and 250 watts. Two e-bike batteries charged in parallel absorb exactly the 400 to 500 watts of net surplus.
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Cordless Vacuum Cleaners, DIY Tools & Powerstations: Connect these devices specifically during the evening hours.
The Role of Smart Plugs and Automation
To avoid having to manually go from socket to socket in the evening, home automation takes over this task.
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Smart Sockets (e.g., Shelly, AVM Fritz!DECT, TP-Link Tapo): Via power measurement or timers, these sockets automatically switch on consumers as soon as a defined surplus is available.
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Home Assistant / iBroker: For ambitious users, scripts can be created: "If the PV power between 6:00 PM and 8:00 PM is above 600 watts for more than 10 minutes and household consumption falls below 200 watts, switch on the e-bike charging station."
Strategy 2: Intermediate Storage – When Does a Battery Storage Make Sense?
Load shifting has natural limits: you don't do laundry every evening, and the hot water tank is heated up at some point. In addition, the main household load (lighting, television, cooking, Wi-Fi) often shifts to the hours after sunset (9:00 PM to midnight).
To save unused evening electricity for the night, using a suitable storage solution is the most effective way.
What Matters When Choosing a Storage System
Those who want to efficiently secure their solar power should pay attention to some crucial quality features:
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Charging and Discharging Power: The storage unit must be able to cover higher household loads, even when cooking in the evening or using several devices simultaneously.
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Multiple MPPT Trackers: In the low evening sun, partial shading often occurs due to trees or neighboring buildings. Independent MPPT inputs ensure that shaded modules do not reduce the performance of the remaining strings.
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Scalability: Household electricity demand changes. A modular system grows flexibly with your requirements.
For users looking for a flexible and powerful solution, retrofitting with a compact head storage unit is an option. A modern model like the SunEnergyXT 500 Pro Head Storage 2400W demonstrates what is technically important: With up to 2,400 watts of system power in grid-connected operation, it offers sufficient power reserves for typical evening peak loads. Thanks to four independent MPPT inputs (up to 2,500 W PV input power), it optimally utilizes module surfaces with different orientations. The system is modularly scalable from 5.024 kWh to 30 kWh and has an integrated emergency power output with a switching time of less than 10 ms.
Economic Comparison: Direct Consumption vs. Load Shifting vs. Storage
To illustrate the savings potential, we compare three scenarios for the period from May to September (150 summer days) with a daily evening surplus of 600 watts over 3 hours each (1.8 kWh surplus/day).
Assumptions:
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Grid electricity price: 38 cents/kWh
-
Daily evening surplus: 1.8 kWh
| Scenario | Daily use of surplus | Savings per summer day | Savings in summer (150 days) |
| Scenario A: No action | 0 kWh (feed-in to the grid) | €0.00 | €0.00 |
| Scenario B: Load shifting only | approx. 0.9 kWh (dishwasher, e-bike) | approx. €0.34 | approx. €51.00 |
| Scenario C: Storage integration | 1.8 kWh (full utilization at night) | approx. €0.68 | approx. €102.00 |
Note: Over the entire year, the effect accumulates further due to spring and autumn yields.
Conclusion: Step-by-Step to Maximum Self-Consumption
A surplus of 600 to 700 watts in the evening is no cause for concern, but rather a sign of a well-functioning solar system. With the right strategy, you can utilize this electricity seamlessly yourself:
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Analyze: Use app data to determine exactly when your surplus window begins.
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Automate: Use smart plugs and timers for large consumers and battery charging stations.
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Store: When load shifting is exhausted, a coordinated storage system ensures that the evening yield covers the electricity demand for the entire night.
Frequently Asked Questions
1. Is a storage unit worthwhile with only 600 to 700 watts of evening surplus?
Yes, absolutely. 600 to 700 watts over a period of two to three hours results in approx. 1.2 to 2.1 kilowatt-hours of pure energy. This amount is often sufficient to cover the complete night consumption of an average household (base load of approx. 100–150 W over 8 hours). This drastically reduces your grid electricity consumption during night hours.
2. Can I operate the washing machine and dishwasher simultaneously if my balcony power plant delivers 600–700 W?
It is recommended to switch on these appliances one after the other. When heating water, both dishwashers and washing machines briefly draw between 1,800 and 2,200 watts. If both appliances heat up simultaneously, you will have to purchase additional electricity from the grid despite the 700 watts of solar power. If one appliance runs first and then the other, you will use the solar power much more efficiently.
3. What happens to the surplus electricity if I have neither a storage unit nor consumers switched on?
For standard balcony power plants without storage, the surplus electricity automatically flows back into the public power grid via your socket. Depending on the installed electricity meter, the following happens:
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Bi-directional meter: The fed-in electricity is registered on the feed-in meter (usually without remuneration for balcony power plants).
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Meter with backstop: The meter simply stops; the electricity goes into the grid without remuneration.
4. How do smart sockets help to automatically utilize the evening yield?
Smart sockets measure power or communicate with the electricity meter or the inverter app. As soon as it is determined that the feed-in to the grid exceeds a threshold (e.g., 400 watts), the socket automatically switches on the connected consumer (e.g., a domestic hot water heat pump or an e-bike charger) and switches it off again when the solar power decreases.
5. Which orientation of the solar modules helps to utilize the evening sun even better?
A west or southwest orientation of the modules is ideal for generating evening electricity. While a purely south orientation reaches its peak around noon (12:00 to 1:00 PM), west-facing modules still deliver high power values, especially between 5:00 PM and 8:30 PM.
6. Is a battery storage unit for balcony power plants also useful in winter?
In winter, the total yield of solar systems is lower, so the storage unit is less often fully charged. Nevertheless, even on sunny winter days, the storage unit captures the few yield peaks. In addition, modern storage systems with an emergency power function offer an additional plus in reliability in the event of grid disturbances in winter.
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