Introduction
One of the frequent questions I receive regarding the SOLAR STATION and SPOT STATION projects is how I can save. I wrote this article based on my personal experiences with photovoltaics and spot prices.
Our home is fully electrified - we heat with a heat pump that also heats the hot water. We drive two electric cars. On the roof, we have a photovoltaic system of about 10kWp with an 11kWh battery.
In the autumn of 2024, after the end of the fixed rate period, I switched to spot prices. You can find out what spot prices are here.
Energy Consumption
The key to saving is controlling the largest consumers in the home. I approached this based on the highest consumption.
To optimize consumption, I used my own SOLAR STATION and SPOT STATION products in combination with smart plugs from Shelly – I call them SOLAR PLUG.
The main difference between these two products is that SPOT STATION is intended for customers without photovoltaics with a flow meter. SOLAR STATION is for owners of supported photovoltaics. So, if you have a photovoltaic system, it is better to choose the SOLAR STATION product, which can control the SOLAR PLUG also according to spot prices.
SOLAR STATION cannot actively control inverters – so-called energy trading, this function is beyond my capabilities. In my projects, I focus on optimizing consumption using smart plugs. In my personal opinion, today's spot electricity selling price is so low that it is not worth dealing with.
EV Charging
Electric cars are the largest consumers in our home. In the summer period, we charge the car according to the rules of photovoltaics and the battery. In the winter period, we charge the EV according to spot prices – here I use the rule of the 6 cheapest hours of the day.
Controlling EV charging is not that complicated. The advantage is that if you drive near chimneys, it is enough to charge a few kWh each day. There is no need to always charge the entire battery.
Charging can be smartly controlled in the following ways:
- SOLAR PLUG (cheap solution)
You can, for example, use this 3600W plug. The plug can be paired and controlled with my stations according to the rules of photovoltaics and spot prices. You connect the original single-phase charger from your car's manufacturer to the plug.
Charging is slow, but it can be perfectly utilized in the summer according to the rules of photovoltaics. The charging power is about 3.3kWh, which is just enough for my 10kWp system. In the winter, we then charge according to the 6 cheapest hours of the day (which usually falls at night) and about 20kWh are charged (120km range).
- EcoVolter PRO (professional solution)
We also support excellent charging cables (portable wallboxes) EcoVolter PRO.
SOLAR STATION can then dynamically control this cable depending on surpluses or the battery's charge state, maximizing your photovoltaics. In the winter, you can then charge again according to spot prices, and during the 6 cheapest hours, you can charge up to 66kWh, which usually fully charges the battery.
- SOLAX Wallbox
If you have a SOLAX inverter and wallbox, you can use SOLAR STATION to control the wallbox according to spot prices. You can set the ECO mode on the wallbox to switch according to specified rules.
Heat Pump
Heating is our second largest consumer. The main idea for saving is whether it is necessary to have the heat pump on 24 hours. It turns out that it is sufficient to have the heat pump on, for example, only 12 hours a day. I have utilized this and turn the heat pump on during the 12 cheapest hours of the day.
In the SOLAR STATION project, I support heat pumps from MasterTherm, Viessmann, and Mitsubishi Zubadan. Control is currently only available for MasterTherm. Unfortunately, heat pump manufacturers did not think enough about remote control via the internet. Therefore, controlling them is quite difficult.
Tip for electricians: Another way to control the heat pump is via the SOLAR PLUG PRO Mini relay. The relay can be easily switched via SOLAR and SPOT STATION. The output of this relay is suitable to be connected to the HDO input of the heat pump. Nowadays, the difference in distribution price (HDO) is not as significant as the price of the power component.
Underfloor Heating
I do not have underfloor heating with resistance wire, but it can also be easily controlled. Therefore, I present a theoretical way to achieve this - I am a theoretical electrician.
Underfloor heating is often connected to two phases. One phase is connected to the thermostat, and this thermostat then switches the second power phase. The power phase can be connected, for example, to the SOLAR PLUG PRO. and this relay can be switched according to spot prices. It will then work according to the following logic – the heating turns on if the temperature drops below a certain threshold AND at the same time the energy price is low (6 or 12 cheapest hours). If I reverse this, you simply will not heat during the price peak.
Hot Water
In my example, we heat the hot water primarily using the heat pump. Secondarily, however, we use direct heating – spirals. This spiral can be easily controlled using a smart plug.
For optimization of heating, I wrote a separate article on the blog.
Washing Machine, Dishwasher, Dryer
Intelligent control of these appliances is complicated. You can use delayed starts, etc. However, this is usually the work of the wife...
However, my wife quite understood that we wash according to smileys. On the SPOT STATION, a commonly discussed smiley is often displayed, which simply indicates whether washing is allowed - there are cheaper hours of the day. It is faster than studying spot price charts.

Of course, we do not want to be slaves to spot prices, but taking a look at the "smiley on the wall" is not complicated either.
Freezer
If you have a large freezer, you can take advantage of its large thermal inertia. It definitely makes sense to turn it off during the most expensive hours of the day. For this, you can also use small 2500W plugs. The plug can then be switched according to spot prices - even in the summer. However, it must run for at least 12 hours. The cheapest times in the summer overlap with the peak production of photovoltaics.
Battery Charging at Night
In the winter months from October to February, I set the battery charging from the grid. I made this setting directly in the inverter and charge the battery to 100% during the night hours from 03:00 to 04:00, when the price is usually favorable. This prepares the home for the morning peak. During the winter months, we manage to consume 100% of the electricity from the PV system, so why not buy cheaply at night.
Of course, charging the battery only makes sense if you are buying at spot prices.