The Freedom of Energy Independence: A Guide to Calculating Solar Panels for Your Home

In the modern world, the freedom of living in your own home is increasingly perceived as energy independence. Alternative sources of energy offer the potential to significantly reduce costs and, ideally, completely eliminate reliance on centralized and, most importantly, very expensive resources.

The Transition to Autonomy

When choosing solar panels for your home, it’s important to understand that it’s not yet possible to fully transition heating to green energy. This “delay” is due to the imperfections of the housing itself. For any alternative stations, it’s crucial that heat losses are minimal, i.e., the house is well insulated. The second issue is the mode of power generation. The bulk of the resource from solar panels (70%) falls between April and September. During the rest of the time – the heating season – about 30% can be generated, and this amount directly depends on the number of sunny days.

An Example of an Average Calculation for the Middle Belt

Annually, a 100 m^2 cottage with insulated walls and ceilings requires approximately 11.5 MW of energy. Solar panels of 10 kW produce roughly the same amount – this opportunity corresponds to 30 panels with 72 elements (1.64 x 0.99 m, 350W power). However, such a station gives its maximum in the warm period of the year when heating is not used. In the winter months, the power decreases to 10-15 kW per day (depending on the weather), which is significantly lower than the needs of the heating circuit. Every day, a 100 square meter house requires 120 kW.

Can Heating Costs Be Reduced Using Solar Energy?

To reduce costs, you need to include another link in the scheme – the green tariff. By generating and selling excess energy in the summer period, it is possible to compensate for part of the heating costs.

When deciding to buy solar panels, you can save significantly on hot water production – on average, costs are reduced by 70%. If you have a house with a pool, the savings will be even more substantial. The greatest effect can be achieved at the construction stage when the solar station is calculated and designed together with the main circuit. In this variant, other natural sources of generation, such as heat pump systems, can be added to the solar panels. A comprehensive solution will reduce energy consumption by 4-5 times, thus minimizing dependence on electricity, gas, and solid fuel suppliers.

How Many Panels Will Be Needed

To provide yourself with energy in the summer period and sell excess energy through the green tariff, you can install a set of solar panels with a capacity of 30 kW (until recently, you could only install a maximum of 10 kW).

In the calculation, you will need a free area on the roof where you can fix the panels. The areas should not be shaded by tree crowns or nearby buildings. It is advisable to orient the surfaces in the southern direction – the difference with the northern roof slope is about 40%, and this figure will also have to be taken into account.

After calculating the free area of solar panels for the home, it needs to be converted into the number of panels.

The result is divided by 2 (1.96×0.99=1.94 m^2 or ~ 2 for panels with an increased area). For 1.6 (1.64×0.99=1.62 or ~ 1.6 for standard modules).

A preliminary estimate gives about 90% accuracy. Knowing the number of individual elements, you can proceed to calculate the power. Each standard panel generates about330-350 W. Knowing which solar panels you will be installing, multiply the result of dividing the roof area by the performance to get the final power.


The free roof area is 120 m^2. For installation, solar panels of 330 W with an area of each panel of 1.6 m^2 are chosen.

We calculate the number of panels: 120 m^2 : 1.6 m^2 = 75 pcs. The power of the station will be 75 x 330 W = 24.75 kW.

Main Energy Consumers:

NamePower Consumption, kWhDuration of Operation, h/dayTotal Daily Power, kWh
Washing Machine20001.53000
Electric Kettle20000.15300

Is It Profitable?

On average, a 15 kW station allows you to profit from the sale of energy of about $2200 US, if the object consumes within 250 kW per month. Calculations for the green tariff are tied to the € rate, so profitability will always remain at the same level. The payback period for investments is 5 years with a profitability of 20%.

Tasks for Solar Panels

In case of power outage, solar panels can work as a backup power source. For this purpose, a moderate power of 3-5 kW is sufficient.

If the station is intended to be used on a permanent basis as a replacement for the central network, it is necessary to design a system with battery packs that will accumulate the generated energy. In this case, it is necessary to estimate the peak load.

To calculate, you need to note the readings of the meter, then turn on all electrical appliances for a certain time, take repeated readings, and convert the resulting consumption figure to one hour. For example, you got 5 kW. This means that the station should give a similar power at a peak moment.

The average consumption per day is calculated from receipts. The amount for the year is taken, divided by 365 days, and multiplied by the correction coefficient 1.2. Suppose you got 10 kW. This amount should be generated by solar panels every day, i.e., you need a station of about 10 kW (it is better to put with a margin of 12-15 kW).

A power of 10 kW corresponds to 30 panels of 330 W. The next step is the choice of batteries. In the case of Gel and AMG, having a capacity of 250 A·h, you need to purchase 8 elements. If you switch to lithium iron phosphate batteries, you will need 4 devices. To ensure that the station gives the required 5 kW at the peak moment, an inverter is included in the system, converting direct current into alternating current.

The Cost of Solar Panels

The cost of solar panels operating in autonomous mode is between $17,000 and $25,000 US, which is quite a lot. If there is an opportunity to include the central power grid in the scheme, it should not be refused. In combined mode, it is possible to use the station’s capabilities to the maximum in the summer by selling excess energy through the green tariff, and in winter thedifference between the station’s performance and actual needs will be covered by the resource supplier.

The Current Situation and Future Prospects

The current situation and prospects for the development of alternative methods show that in the near future, energy generation from natural sources will become a primary scheme. Therefore, it’s reasonable to connect to renewable energy today.