Day-night battery
Stores the daytime surplus for the following night.
- Self-sufficiency
- 63%
- Self-consumption
- 52%
- Battery size
- 1.3 kWh/kWp
Available now Last verified 19 June 2026
Commercial solar & battery storage in Belgium
Market facts the model runs on
Primary-source values, each with its source and confidence level.
Grid tariff saved (self-consumption)
€0.280/kWh
Solarnation reference value for Flanders, 2026
Export / feed-in remuneration
€0.045/kWh
Solarnation reference value for Flanders, 2026
Capacity tariff (monthly peak)
€53/kW/yr
Fluvius distribution tariffs 2026
Diesel generation cost avoided
€0/kWh
Not applicable in Belgium
High confidenceMediumTo be confirmed
Solar autonomy scorecard · Modelled estimate
How far solar and a battery go in Belgium
With PV sized at 120% of annual consumption, a battery that carries one night covers 63% of the demand in Belgium; a battery holding three days of consumption lifts that to 73%.
Generation is strongly seasonal: the strongest month yields 5.7× the weakest, and the weakest month delivers only 2.4% of the annual yield.
In the three leanest months 20.0% of the annual consumption stays uncovered (167 kWh per kWp). Short-term storage cannot close that gap; it takes the grid, a backup source or seasonal storage.
Businesses pay on average 0.263 USD per kWh, households 0.406 USD per kWh.
The configurator for Belgium calculates with 950 kWh/kWp, a site-specific reference (Solarnation reference value for Flanders, 2026). This scorecard uses 1,000 kWh/kWp, a rounded national estimate, so that all countries are compared on the same basis. Its seasonal figures likewise come from the climate model, not from the site-specific monthly profile above.
The market facts above use the tariff a medium-sized business actually pays in Belgium: €0.280 per kWh. The business price in this scorecard is a cross-country average over all business tariff classes, used only to compare countries.
- Electricity price, businesses
- 0.263USD/kWh
- Electricity price, households
- 0.406USD/kWh
- PV yield
- 1,000kWh/kWp
- Seasonal spread
- 5.7×strongest ÷ weakest month
- Three-day battery
- 6.8kWh/kWp
- Lean-season deficit
- 20.0%of annual consumption
Two battery scenarios
Both with PV sized at 120% of annual consumption.
Three-day battery
Holds three full days of consumption, to ride through overcast spells.
- Self-sufficiency
- 73%
- Self-consumption
- 61%
- Battery size
- 6.8 kWh/kWp
Generation and demand through the year
Share of the annual total per month. Modelled from latitude and climate class, not measured.
- Weakest month
- 2.4%
- Strongest month
- 13.9%
- Seasonal spread
- 5.7×
- Consumption profile
- winter peak (heating)
- Climate class
- maritime
PV yield / Consumption — Belgium
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| PV yield (%) | 2.8 | 4.4 | 10.0 | 12.1 | 13.6 | 13.9 | 13.1 | 11.8 | 7.7 | 5.1 | 3.1 | 2.4 |
| Consumption (%) | 10.3 | 9.8 | 9.0 | 8.2 | 7.4 | 7.0 | 6.6 | 6.6 | 7.4 | 8.2 | 9.4 | 10.3 |
A winter deficit short-term storage cannot close
In the three leanest months 20.0% of the annual consumption stays uncovered (167 kWh per kWp). Short-term storage cannot close that gap; it takes the grid, a backup source or seasonal storage.
Sensitivity: what changes the outcome
One parameter varied at a time against the base run.
| Parameter | Value | Day-night | Three-day | Deficit |
|---|---|---|---|---|
| base | 120% · 55% · 92% | 63% | 73% | 20.0% |
| PV oversizing | 100% | 59% | 69% | 21.6% |
| PV oversizing | 150% | 67% | 78% | 17.6% |
| Night fraction of consumption | 45% | 63% | 73% | 20.0% |
| Night fraction of consumption | 65% | 62% | 73% | 20.1% |
| Battery round-trip efficiency | 85% | 61% | 73% | 20.1% |
| Battery round-trip efficiency | 96% | 64% | 73% | 20.0% |
Going from 120% to 150% PV moves three-day self-sufficiency by only 5 points: the signature of a seasonal problem, not a sizing problem.
Every modelled value for Belgium
The same fields as the downloadable dataset, with their definition.
| Variable | Value | Definition |
|---|---|---|
Continentcontinent | Europe | Continent the country belongs to. |
Countrycountry | Belgium | Country name in English. |
Regionregion | — | Climate region within the country; empty when the country is modelled as one region. |
Electricity price, householdsprice_households_usd_mwh | 0.406 USD/kWh USD/MWh | Average all-in retail price for households, national average. Static average, not a dynamic or market price. |
Electricity price, businessesprice_businesses_usd_mwh | 0.263 USD/kWh USD/MWh | Average all-in retail price for businesses, national average. Empty where the source publishes no business price. |
PV yieldpv_yield_kwh_kwp | 1,000 kWh/kWp/year | Estimated annual yield of a well-oriented PV system per installed kWp, rounded to the nearest fifty. |
Weakest month shareweakest_month_share_pct | 2.4% | Share of the annual yield produced in the weakest of the twelve months (the wet season in monsoon climates, winter elsewhere). A perfectly flat year gives one twelfth per month. |
Strongest month sharestrongest_month_share_pct | 13.9% | Share of the annual yield produced in the strongest of the twelve months. |
Seasonal spreadseasonal_spread | 5.7× | Strongest month divided by weakest month. Close to one means flat generation all year; above ten means strongly seasonal. |
Self-consumption, day-night batteryself_consumption_daynight_pct | 52% | Share of the PV generation that is used on site with a battery sized to carry one night. Equals self-sufficiency divided by the oversizing factor. |
Self-sufficiency, day-night batteryself_sufficiency_daynight_pct | 63% | Share of the annual consumption covered by PV plus a battery sized to carry one night. Never above one hundred percent. |
Battery size, day-nightbattery_daynight_kwh_kwp | 1.3 kWh/kWp | Battery capacity needed to carry the night-time share of one day of consumption, per kWp of PV. |
Self-consumption, three-day batteryself_consumption_3day_pct | 61% | Share of the PV generation that is used on site with a battery holding three days of consumption. |
Self-sufficiency, three-day batteryself_sufficiency_3day_pct | 73% | Share of the annual consumption covered by PV plus a battery holding three days of consumption. This is the figure the energy-island assessment is based on. |
Battery size, three-daybattery_3day_kwh_kwp | 6.8 kWh/kWp | Battery capacity equal to three days of consumption, per kWp of PV. |
Consumption profileconsumption_profile | winter peak (heating) | Assumed seasonal shape of demand for the climate: winter peak (heating), summer peak (cooling), double peak or near-flat. |
Lean-season deficitwinter_deficit_pct | 20% | Demand that stays unmet during the three consecutive lowest-yield months, despite the three-day battery, as a share of annual consumption. It is what remains for the grid, a backup generator or seasonal storage. |
Lean-season deficit, absolutewinter_deficit_kwh_kwp | 166.9 kWh/kWp | The same deficit expressed in kWh per kWp of PV. |
Latitudelatitude | 50.8 ° | Representative latitude used by the astronomical yield model; negative is the southern hemisphere. |
Climate classclimate | maritime | Climate class that sets the monthly cloud pattern, day-to-day variability and consumption profile. |
Monthly yield sharesmonthly_yield_share_pct | 2.8 · 4.4 · 10.0 · 12.1 · 13.6 · 13.9 · 13.1 · 11.8 · 7.7 · 5.1 · 3.1 · 2.4 | Twelve values, January to December: share of the annual PV yield per month. Modelled from latitude and climate class, not measured. |
Monthly consumption sharesmonthly_consumption_share_pct | 10.3 · 9.8 · 9.0 · 8.2 · 7.4 · 7.0 · 6.6 · 6.6 · 7.4 · 8.2 · 9.4 · 10.3 | Twelve values, January to December: assumed share of the annual consumption per month. |
How the model works
Monthly PV yield comes from an astronomical model (latitude, declination, tilt) multiplied by a climate pattern for cloud and rain. Day-to-day variability follows a gamma distribution per climate; multi-day coverage is the sum of independent days. Seasonal consumption is set per climate: a winter peak for heating, a summer peak for cooling, a double peak in Mediterranean climates.
Fixed assumptions
PV sized at 120% of annual consumption; 55% of consumption falls outside direct sun hours; battery round-trip efficiency 92%.
What it is not
An analytical approximation, not an hourly simulation of your site. Prices are static national averages, not dynamic or market prices. The deficit is not a storage recommendation: it quantifies what remains for grid, backup or seasonal storage.
Sources
- Electricity prices: national averages, Q2 2026.
- PV yield: Estimates in line with Global Solar Atlas (World Bank / Solargis), rounded to the nearest 50 kWh/kWp.
- Licence: CC BY 4.0.
- Dataset updated 2026-09-19
Local partner
Installation, permits and after-sales run through our local partner; Solarnation designs, sizes and finances. Your case study is handed over to them after the last step.
Local partner to be announced.
Belgium — solar autonomy in short
Can a business in Belgium go off-grid with solar and a battery?
With PV sized at 120% of annual consumption, a battery that carries one night covers 63% of the demand in Belgium; a battery holding three days of consumption lifts that to 73%. In the three leanest months 20.0% of the annual consumption stays uncovered (167 kWh per kWp). Short-term storage cannot close that gap; it takes the grid, a backup source or seasonal storage.
How large a battery does solar autonomy take in Belgium?
Per kWp of PV, carrying one night takes about 1.3 kWh of battery and holding three days of consumption about 6.8 kWh. With the three-day battery, self-sufficiency reaches 73%.
How much does solar generation in Belgium vary between seasons?
A well-oriented system yields about 1,000 kWh per kWp a year. The strongest month produces 5.7× the weakest: 13.9% against 2.4% of the annual yield.