Seasonal solar planning
How much does a 5 kW solar system produce in winter?
Location makes a large difference. The same reference array averages about 4.1–16.4 kWh a day in December across the four cities below. An individual cloudy or snowy day can be much lower.
A 5 kWp array in London, Berlin, Warsaw and Madrid.
Here “5 kW solar” means 5 kWp of rated panel capacity, not a 5 kW inverter or a constant 5 kW output. The examples share the same assumptions: south-facing panels, 35° tilt and 14% system losses in the PVGIS calculation.
Each cell shows modelled monthly energy and that month’s average daily energy. June is included to show the seasonal difference. City names open the local forecast and full seasonal profile.
| City | October | December | January | June |
|---|---|---|---|---|
| London | 343 kWh11.1 kWh/day | 182 kWh5.9 kWh/day | 204 kWh6.6 kWh/day | 613 kWh20.4 kWh/day |
| Berlin | 350 kWh11.3 kWh/day | 136 kWh4.4 kWh/day | 158 kWh5.1 kWh/day | 663 kWh22.1 kWh/day |
| Warsaw | 357 kWh11.5 kWh/day | 126 kWh4.1 kWh/day | 165 kWh5.3 kWh/day | 676 kWh22.5 kWh/day |
| Madrid | 632 kWh20.4 kWh/day | 509 kWh16.4 kWh/day | 541 kWh17.4 kWh/day | 772 kWh25.7 kWh/day |
Source and calculation: European Commission Joint Research Centre PVGIS 5.3; stored profile dated . Monthly and daily values are scaled by 5 ÷ 10 from the reference dataset, then rounded for display. The date identifies the stored calculation, not the weather period of a forecast.
These are multi-year averages for the selected city coordinates. Your roof direction, tilt, nearby shade, snow, equipment and operating limits can change the result. The table does not describe every roof in a city or guarantee a minimum winter day.
Why an annual average overstates the winter plan.
The Berlin reference produces about 5,247 kWh in a typical year. Dividing that by 365 gives about 14.4 kWh per day. But its December profile averages only 4.4 kWh per day. Using the annual average to plan December battery charging would assume energy that often is not available in that season.
A monthly daily average still smooths over clear and overcast days. It helps answer “is this season usually weaker?” rather than “can I charge the car tomorrow?”. For the second question, use the dated solar production forecast and check the hourly curve.
Less winter sunlight matters more than the panel rating.
Shorter daylight hours, a lower sun and local weather reduce the useful solar window. Shadows can reach a roof that is unshaded in summer, while snow cover may restrict production further. A 5 kWp rating describes test conditions, not what the array must produce at noon in December.
If output falls unexpectedly, compare equivalent weather and periods, check inverter alerts and look for an obvious change in conditions. The forecast-versus-actual checklist helps distinguish a measurement mismatch from a change that merits an installer check.
Worked example · illustrative numbers
Will winter solar fill a 10 kWh home battery?
Suppose tomorrow’s dated forecast is 6 kWh and the home will use 4 kWh during the PV hours. If those loads overlap with generation, about 2 kWh is left for charging. At an assumed 95% charge efficiency, that adds about 1.9 kWh to the battery. It does not fill an empty 10 kWh usable battery.
This is an invented energy budget, not one of the monthly city averages. It also assumes enough battery room and charging power. A different day, load profile or roof can produce a different result. A battery shifts available energy; it does not make up a seasonal generation shortfall.
Use the overnight charging example to plan the gap while preserving reserve. If the battery can legally and technically charge from the grid, compare the actual retail tariff and charging losses before setting a schedule.
Which household jobs can wait for the winter solar window?
- EV charging: use surplus while the car is home, but keep enough time for a departure-time fallback.
- Hot water or heating: move a useful, supported run into a sustained window if comfort and manufacturer safety controls allow it.
- Appliances: choose flexible cycles that are actually needed. Check their power and safe-use instructions rather than starting everything at the forecast peak.
- The battery: leave room for likely surplus when it exists, but do not lower protected reserve just to match a seasonal average.
Check tomorrow’s solar forecast for your location and roof before committing those loads.
FAQ
Winter solar questions.
How much does a 5 kW solar system produce per day in winter?
There is no single figure for every roof. In the four PVGIS reference examples on this page, a 5 kWp south-facing array at 35° tilt averages about 4.1–16.4 kWh per day in December. These are multi-year monthly averages, not a range guaranteed for an individual day.
Do solar panels still work in winter?
Yes, when light reaches the panels. Shorter days, the lower sun, clouds and snow can reduce daily production. A low winter day alone does not show that the system is faulty.
Can a 5 kWp solar system fill a 10 kWh battery in winter?
Sometimes, but a panel rating cannot answer that on its own. Compare that day’s PV production with simultaneous household demand, then allow for charging losses, battery space and charge-power limits. A monthly average is not enough to promise a full battery tomorrow.
Is 5 kWp the same as 5 kWh?
No. 5 kWp is the rated peak power of the panels under standard test conditions. kWh measures energy produced over time. A 5 kWp array does not continuously produce 5 kW or guarantee 5 kWh every hour.
Can I scale these winter figures to a 3 kWp or 10 kWp system?
For a rough comparison under the same roof and loss assumptions, multiply the 5 kWp values by 0.6 for 3 kWp or by 2 for 10 kWp. Real changes in shading, inverter sizing or clipping can make a particular installation behave differently.
Sources
Data and assumptions.
- European Commission JRC: PVGIS user manual
Explains the climate-based output, peak-power units, roof inputs and system-loss assumptions used for PVGIS estimates.
- European Commission Joint Research Centre PVGIS 5.3
Table calculated from GridPassport’s stored PVGIS monthly profiles (4 August 2026), scaled from 10 to 5 kWp. These are model outputs, not measurements from four homes.
- Tesla: understanding solar system performance
Manufacturer guidance on seasonal production, cloud, snow and the difference between power and energy.
Make it personal
Forecast your own roof, then get tomorrow by email.
Use your location and system size instead of a generic benchmark. The result includes expected output, uncertainty and the strongest solar hours.