Energy independence: standalone heating and electricity generation

Standalone heating and electricity generation: energy independence for more self-sufficiency

Homeowners who cover 100 percent of their domestic energy demand for heating energy, DHW and household electricity themselves benefit from energy independence. Put simply, this means independence from public utilities and no more bills for your own energy consumption. In addition, standalone supply also means a major contribution to environmental and climate protection. After all, energy independence can only be achieved with renewable sources. Using tried and tested technologies, Viessmann makes the step towards an energy-independent home possible. You can read more on this topic in the following sections.

Difference between true energy independence and that on the balance sheet

Homes that generate a large part of the energy they need themselves, perhaps through electricity or heat from a solar system, can be described as energy-independent. It is important to point out the difference between "true" and "balance sheet" self-sufficiency.

• A fully standalone energy supply: if a home actually meets its energy demand entirely on its own, this is referred to as true self-sufficiency in energy supply. As a result, connection to an external power or heat supply is no longer necessary.
• Balance sheet standalone energy supply:  if the energy gains that an independent building enjoys each year roughly correspond to its consumption values, it can be referred to as energy-independent on the balance sheet. A good example is the "zero energy house", which generates as much energy itself as it consumes.

Buildings whose energy balance is in equilibrium –– i.e.  which are energy-independent on the balance  sheet –– are not automatically independent of the external supply. This is because there is a seasonal gap between the generation of energy and the peak demand: while the photovoltaic system produces a surplus of energy in the summer, its yield in winter is barely sufficient to meet the increased demand. The imbalance can be redressed by relying on external power supply utilities. In this way, therefore, homeowners are not completely independent. Technical solutions such as buffer cylinders and power storage units from Viessmann offer a remedy here. The technical requirements for their use are explained below. Storage solutions significantly increase a building's energy independence.

Degree of self-sufficiency: step by step to energy independence

The energy independence of a building can be differentiated with a specification in degrees. The degree of self-sufficiency is based on comparing the required energy with the self-generated energy to provide a numerical value. The higher the  number, the higher the energy independence. Conversely, this means that the higher the degree of self-sufficiency, the lower the dependence on the public grid, power supply utilities and the prices for fossil fuels on the global market. For each building unit considered, degrees of self-sufficiency can be distinguished in terms of:

• Electricity
• Heat
• Total energy

A home can be up to 100 percent independent in terms of electricity, in which case it does not require a connection to the public grid or to purchase utilities. But this says nothing about its independence in the production of heating energy and DHW. In this era of fluctuating fuel prices and awareness for climate protection, the goal is to be as independent as possible. Even if "true" and 100 percent independence in total energy demand is not achieved immediately, step-by-step implementation of the goal avoids high costs in the future and helps to meet climate protection goals.

Energy independence in new build: prerequisites, planning and options

Achieving energy independence in new build requires solid planning. This is because all components of a building need to be optimally matched. Thus, the enveloping surfaces need to lose only minimal energy, while transparent components, such as windows and doors, need to allow ample solar energy into the house in winter. Electrical appliances should also work particularly efficiently to reduce electricity consumption to a minimum. If these conditions are met, the chances are high that from an economic perspective, a building can be operated independently of electricity.

Special simulation programs are available to allow potential interactions in the later supply to be considered during the planning stage. This way, the structural foundations and the technical conditions can be determined well before the foundation stone is laid, such that an optimal, independent energy supply is accomplished.

Three combinations compared: three combinations of installed components can be used to take a closer look at the independent heat and power supply in a newly built home:

• Photovoltaics and solar thermal systems
• Photovoltaics and heat pump
• Photovoltaics and fuel cells

Independent heating with photovoltaics and solar thermal: independent heat supply all year round thanks to solar energy

Photovoltaics (PV) in combination with solar thermal covers the annual heat demand of a home. First and foremost, a solar thermal system does this through large-surface solar collectors that are installed on the roof and feed the heat yield into a buffer cylinder. In this case, this is one water cylinder for a detached house. This way, the thermal energy can be stored for a long time before it is increasingly used for heating and DHW heating in the colder months. Then, the heating system in use simply draws heat directly from the cylinder to heat rooms and DHW. If the conditions are favourable, homeowners who heat independently in this way can manage until spring with the energy they have stored, without having to put a booster heater into operation. Optionally, the full degree of self-sufficiency can also be achieved in the power supply by installing a power storage unit, such as the Vitocharge VX3.

Heat pumps and photovoltaics used together increase energy independence –– provided that the building is well insulated and that electrical appliances used in the household are not unnecessary "power guzzlers". In addition, the solar modules and the power storage unit of the solar system should be sufficiently large to ensure a supply even in the darker months of the year.

Standalone heating with a fuel cell and photovoltaics –– year-round independence thanks to hydrogen

Combined with a photovoltaic system and a power storage unit, the fuel cell heating system ensures an independent supply of electricity and heat all year round. The electricity yield of the photovoltaic system is used to supply the household and the electric vehicle, especially in the summer. Surplus yields can be captured in a battery storage system, such as the Vitocharge VX3. When it gets darker and colder outside, the heat generator, in this case the fuel cell, can increasingly take over power generation. If the solar PV system is large enough, it can also cover the demand in winter thanks to the storage unit and thus help to achieve a high level of self-consumption and self-sufficiency.

Energy independence in a detached house –– what pays and when?

Technically speaking, a fully independent heat and power supply is only worthwhile if the collectors and cylinder are of generous dimensions. The ratio between the energy costs saved and the initial investment made must, therefore, remain within a certain range so that amortisation is possible. For a detached house, it is therefore generally uneconomical to aim for full independence at 100  percent. Instead, it is recommended that a home achieve as high a degree of self-sufficiency as possible and still –– even if only at peak load times –– to fall back on the connection to the public grid for electricity and heat. Apartment buildings, local authorities and industrial properties, on the other hand, can benefit from the greater financial and technical effort of full independence in the long term. For this, solid planning and responsible use of the technical options and one's own resources are indispensable.  

Check energy providers and switch if necessary: opting for green gas and green electricity promotes the expansion and use of renewable energies. That's why it's worth putting your own providers through their paces and thinking about switching if necessary. Doing this gives us control over where the energy we consume comes from and from which sources. 

Focus on energy efficiency in household appliances: it's not only worth paying attention to efficiency when it comes to heating – are you planning to buy a new washing machine, a new refrigerator or other appliances for the kitchen and recreational room? Then look at their energy efficiency class and how much electricity the appliances consume. Nothing is more efficient than plugging energy gaps in the long term and pulling the plug on the power guzzlers of yesteryear.

Heat less and more sensibly: even the most efficient and exemplary heating system can make savings if it is used in moderation and is optimally adjusted to real heating and hot water demand. After all, the cheapest energy is energy that is not consumed in the first place. And, speaking of attitude: use today's smart home technology and intelligent asset management to save energy costs. Viessmann can help you with innovative solutions for the regulation and control of energy generators.

Save domestic hot water: do we really need all the hot water we consume every year? When it comes to domestic hot water in particular, a lot of energy can be saved through a simple change of habits – for the sake of the environment and your own wallet. So, when you think about independent heating, consider independent water use as well. Smart products to help you include intelligent shower heads and other methods to optimise hot water consumption. 

Energy modernisation: there are many measures for optimising the energy efficiency of your own home. From hydronic balancing of the heating system to better insulation of façades and windows. This not only exploits savings potential, but also increases the value of the property. You can find out more about the individual options in our energy efficiency guides, for example.