Use our free solar panel calculator UK to estimate how much solar power your home may need. The calculator considers your household electricity use, location, roof direction and shading. You can also include the electricity required for a heat pump and an electric car.
Your estimate updates automatically as you enter your information. It shows the approximate solar array size, number of panels, roof area required, expected annual generation and estimated installation cost.
Your electricity use
I do not know my annual electricity use
This estimate removes the standing charge before converting the bill to kWh.
No saved heat-pump result was found. We can estimate the electricity use, but a completed heat-loss calculation will be more accurate.
Complete the Home Heat Loss Calculator for a more accurate estimate.
The estimate includes 10% charging losses.
Roof and location
Panel choice
How does the solar panel calculator work?
The amount of electricity a solar system can generate depends on more than the number of panels. Your location, roof direction, roof pitch and shading all affect the amount of sunlight that reaches the panels.
The calculator first estimates your total annual electricity requirement. It then estimates the solar array size needed to generate a similar amount of electricity over a year.
Should I include a heat pump?
If you already have a heat pump, or plan to install one, select the heat-pump option. A heat pump can significantly increase household electricity use even though it uses energy much more efficiently than direct electric heating.
If you have already completed our Home Heat Loss Calculator, the solar calculator can use that information when the two calculators are connected. Otherwise, it can make an approximate estimate based on the size and insulation of your home.
For greater accuracy, complete the Home Heat Loss Calculator before sizing a future solar system.
How much electricity does an electric car use?
An electric vehicle can add several thousand kilowatt-hours to annual household electricity use, depending on mileage and vehicle efficiency.
Enter your expected annual mileage and the calculator will estimate the electricity required for home charging. The estimate also allows for energy lost during charging.
How many solar panels will I need?
The number of panels depends on both the required system capacity and the output of each panel.
Higher-output solar panels can produce more electricity from a limited roof area. They can therefore be particularly useful where roof space is restricted.
The calculator lets you choose a panel type or allow the system to recommend one.
Is 4 kW the maximum solar system size?
No. UK homes can install solar arrays larger than 4 kW.
The figure often associated with domestic solar is the 3.68 kW per-phase grid connection threshold used in the simpler G98 connection process. Larger systems may require a different connection process or approval from the Distribution Network Operator.
Your roof, electricity requirements and grid connection should determine the appropriate system size rather than treating 4 kW as an absolute maximum.
Should I install more solar than I currently need?
Where roof space, budget and the grid connection allow, installing additional capacity can make sense. Future electricity use may increase if you add a heat pump, electric vehicle or other electrical equipment.
The calculator therefore shows the solar generation needed to match your estimated annual electricity requirement. An installer can then assess whether installing additional capacity is worthwhile.
What about solar batteries?
This calculator concentrates on solar generation and panel sizing.
A battery serves a different purpose. It stores electricity generated during the day so that more of it can be used later rather than exported to the grid.
We will treat battery sizing separately because the best battery capacity depends on when you use electricity, your solar generation pattern, tariffs and how much electricity you want to store.
One thing I have deliberately left flexible is the connection to your existing heat-loss calculator. The new plugin looks for several common saved-result formats, but I don’t yet know exactly how your current heat-pump plugin stores its result. If you send me the PHP/plugin file for the existing Home Heat Loss Calculator, I can wire the two together properly so the solar calculator automatically picks up the real result rather than estimating it.