Off-grid new build and the E-level: what counts?

An off-grid house must meet the same EPB rules as any new build. Solar panels lower the E-level, whether the house is connected or not. A battery and a generator do not count for a home. That is why the E-level tells you little about winter: an off-grid system is sized on December, the E-level on a whole year.

You are building a large new house, and you want it to run on its own energy. Your EPB reporter, the adviser who calculates the E-level, asks how many solar panels you plan. Your installer asks something else: what must still run in a dark week in December? On Belgian forums, builders are blunt about it. "I am laying panels to reach my E-level." Reaching it with solar panels "was simply the cheapest way".

Here is what nobody tells you. The E-level and an off-grid system look at the same roof, but they count differently. The E-level subtracts the full yearly yield of your panels, summer and winter alike. Without a grid, summer power the battery cannot store is simply lost. So a house can score an excellent E-level and still run short in January. And the two parts that carry you through winter, the battery and the generator, do not appear in the E-level at all.

In Lokeren, a private house was built without any grid connection. To reach the E-level, solar panels had to be placed anyway. We gave the flat roof the panel layout the off-grid system needed, with an LFP battery. A back-up generator covers periods of high use or little sun.

Does an off-grid new build still have to meet the EPB rules?

Yes. The EPB rules follow the building permit, not the grid connection.

In Flanders, the EPB rules apply to heated buildings built with a permit or notification and an architect, according to Vlaanderen. A house always counts as heated. Whether a cable runs to the street plays no role. In Wallonia, a new house needs an approved PEB adviser. The initial PEB declaration goes with the permit, the final one follows the works, according to SPW Energie.

Miss a requirement and a fine can follow, in both regions. In Flanders, the E-level on your EPC Bouw is also final: work done after the EPB declaration does not lower it, according to Vlaanderen.

Can you build a house without a connection at all? Read our article on a new building without a grid connection. Building in Wallonia? Read what to ask when you build an energy-autonomous house in Wallonia.

What counts in the E-level of an off-grid house, and what does not?

The calculation looks at heating, hot water, fans and auxiliary energy and cooling. It then subtracts what solar panels or cogeneration produce. Everything else stays outside.

Why do solar panels weigh so much? The E-level is expressed in primary energy, and electricity counts 2.5 times, for the losses in power stations and the grid, according to EPB-pedia. The yield of your panels is subtracted from that total in full. EPB-pedia itself calls the impact on the E-level large, and often the cheapest way to lower it (EPB-pedia).

Wallonia works the same way. The Espec indicator is the primary energy use after subtracting what cogeneration or solar panels supply, according to the Walloon Q-ZEN guide.

Do solar panels count when the house has no grid connection?

Yes. The conditions for counting panels are about where they are and when they were placed, not about a grid.

EPB-pedia sets three conditions: the location of the panels, the moment they were installed and green power certificates. For permits applied for from 2018, all panels on your own site count. That is the plot and adjoining plots of the same owner, so panels on a garage, barn or carport count too. For EPB declarations filed from 20 July 2026, new and existing panels may both count. They may not come from another site, and may not already count for another unit (EPB-pedia).

For an off-grid house this is good news. The system needs a large array for winter anyway, and the E-level gets the benefit of all of it. Very low scores are possible: owners on Belgian forums report an E-level of 6, and even minus 1. Planning panels on an outbuilding? Read whether to connect them to the house or build a separate island.

Does a home battery lower the E-level?

No. For a home, a battery cannot be entered in the Flemish EPB calculation.

EPB-pedia is clear: storage in batteries and power from wind turbines are currently not taken into account. For non-residential projects applied for from 1 January 2027, a battery can be entered, subject to final approval. The credit for solar panels then depends on how much solar power the building really uses, with a bonus for storage. For homes, no battery input is possible yet (EPB-pedia).

In Wallonia, the Q-ZEN guide lists biomass, heat pumps, solar water heaters, solar panels and cogeneration as renewable technologies. A battery is not among them.

So the battery is the part that makes an off-grid house work, and the part the E-level cannot see. Size it on your winter nights, not on the score. Read which home battery really works off-grid and how big the battery of a large home should be.

And the back-up generator?

It is not part of the E-level calculation. It may matter more for the rules after 2030.

The method counts energy for heating, hot water, fans and cooling, and subtracts solar panels and cogeneration. A generator that only runs in grey winter weeks is not in that list. In Lokeren, the generator covers periods of high use or little sun. In As, a fully off-grid installation uses a propane generator next to its panels and battery. Read how a generator and a battery share the work.

Look ahead, though. The European buildings directive makes all new buildings zero-emission from 1 January 2030. A zero-emission building may not cause on-site carbon emissions from fossil fuels, according to the directive. The same text counts renewable fuels burnt on site as renewable energy. How Flanders and Wallonia will apply this to a back-up generator is not yet written down. Ask your EPB reporter before you choose the fuel.

Why does a good E-level not keep an off-grid house running in winter?

Because the E-level adds up a year, and an off-grid house must get through every single day.

Over a year, 10 kWp gives about 10,600 kWh. The four darkest months, November to February, give about 16% of that. December gives about a quarter of June. The E-level counts every kWh the same, whether it arrives in June or in December. Off-grid, what the battery cannot store in June is gone.

Winter is also when a house uses most. The heat pump works hardest when the sun is lowest. So we size an off-grid house on the dark months, and add a back-up source for the longest grey spells. Read what a heat pump asks from a home battery in winter.

Which heating fits both the E-level and an off-grid house?

A heat pump in a very well insulated house. There, the E-level and the off-grid system agree.

In Flanders, a new build with an application from 2025 can no longer get a gas connection. Heating comes from a heat pump, a heat network, a biomass boiler with a heat pump, or direct electric heating. Direct electric heating has a very unfavourable effect on the E-level, except with a very low heat demand (EPB-pedia).

Off-grid, the same logic applies, only harder. Electric heaters draw power exactly when the sun gives least. Every kWh of heat demand you design away is a kWh your battery and generator do not have to supply in January. SPW Energie suggests completing a heat pump with an efficient stove for the coldest periods (SPW Energie).

How do you plan an off-grid new build so both calculations work?

Bring the architect, the EPB reporter and the off-grid installer to one table before the permit is filed.

Three questions save you trouble later. Is the roof designed for the panels winter needs, not only for the E-level? Is there a dry, frost-free technical room for the battery and inverters? Where can a generator stand, with its fuel, away from living rooms and neighbours? Our guide for architects and engineering firms covers the design side. The inspection of an off-grid installation covers the AREI.

How do we design the energy system of an off-grid new build?

We start from what the house must do in January, and check that the design also serves the E-level.

Our engineering office calculates the panels, the inverters, the battery and the back-up generator for your plot and your house. The system can be expanded at any time, and you follow it live. In Lokeren, the preliminary study set the battery capacity, and the battery can still be expanded.

1. Step 1: We list what the house must run in summer and in winter: heat pump, hot water, cars, pool, workshop.
2. Step 2: We read the plans and the EPB pre-calculation with your architect and EPB reporter.
3. Step 3: We size the panels, battery and generator on the dark months, and place the panels where both calculations gain.
4. Step 4: We install, have the installation inspected and follow it with you in real time.

Prefer to keep a grid connection as a back-up after all? See what our home batteries do for a large home. Which connection size to request is in the connection size for an all-electric new build.