Solar sizing
Estimate solar kWp and panel count from annual demand, roof space, orientation and UK location.
Independent UK energy planning
Size your solar panels and home battery before you buy
Use your electricity use, roof and tariff assumptions to estimate solar kWp, panel count, battery capacity, annual savings and simple payback.
Free. No registration. Independent early-stage estimate.
A clearer route through the decisions
From first question to component shortlist
1. Understand
2. Calculate
3. Compare
4. Plan
5. Choose components
Calculate my system
Model solar, battery, EV demand and tariffs
Start with your own household numbers and compare scenarios.
Build a home batteryCompare LFP, rack and second-life routes
Start with capacity, power, protection and complete-system cost.
Reuse an EV batterySeparate pack price from usable-system value
Explore health, chemistry, controls and supported pack families.
Understand UK grid rulesPlan around G98, G99, G100 and your DNO
Keep connection permission, export limitation and SEG income distinct.
More than a panel-count estimate
Explore the whole household energy picture
Home battery sizing
Compare a suggested storage range with your chosen usable capacity and inverter limits.
EV electricity use
Include driving demand once, without accidentally duplicating it in household consumption.
Off-peak tariffs
Explore grid charging and tariff optimisation when a suitable off-peak window is available.
Import and export
See estimated solar generation, household self-use, grid import and electricity exported.
Savings and payback
Use your own tariff and installed-cost assumptions to compare annual benefit and simple payback.
Practical UK guides
Research before spending thousands
Solar panels
How to size a UK solar array
Move from annual kWh and local yield to array kWp and a roof-limited panel count.
Battery storageChoose usable capacity and power
Understand kWh, kW, depth of discharge, timing, losses and off-peak charging.
EconomicsCompare costs, savings and payback
Use complete quotations and separate avoided import from export income.
Electricity demandBuild a better annual-use estimate
Read your bills or smart meter and account for EVs, heat pumps and future demand once.
Cheap-tariff storageUse a battery without solar
Calculate charge-window limits, losses, cycle economics and honest payback.
Nissan LeafStudy a common second-life pack family
Compare generations, remaining capacity and whole-pack integration evidence.
Battery comparisonLFP versus second-life EV storage
Compare voltage, controls, warranty, uncertainty and complete £/usable kWh.
Architecture48 V versus high-voltage storage
See how voltage changes current, equipment and integration demands.
Vehicle energyV2L, V2H, V2G or removed pack?
Understand four different electrical and commercial propositions.
Illustrative UK example
A household using 4,000 kWh a year
Suppose a home has space for ten 440 W panels, giving a 4.4 kWp array. At an assumed yield of 900 kWh per kWp, estimated annual generation is about 3,960 kWh.
If 45% is used directly, around 1,782 kWh avoids grid import before battery shifting. The remaining generation is either stored or exported. Battery value depends on usage timing, losses, tariff spreads and installed cost.
- Annual demand
- 4,000 kWh
- Solar array
- 4.4 kWp
- Panels
- 10 × 440 W
- Estimated generation
- 3,960 kWh/year
Illustrative arithmetic, not a performance or savings promise. Replace the assumptions with details relevant to your home.
UK solar and battery questions
Frequently asked questions
How many solar panels do I need in the UK?
It depends on annual electricity use, panel rating, roof space, orientation and local solar yield. The calculator estimates panel count and array kWp, then limits the result to the roof space you enter.
What size home battery do I need?
Battery sizing depends on how much electricity you use and when you use it. Solar surplus, off-peak charging, usable depth of discharge, power limits and backup goals also matter.
Is a solar battery worth it in the UK?
Not always. A battery can improve self-consumption or shift off-peak electricity, but losses and additional installed cost may worsen simple payback.
Can I include an electric car in a solar calculation?
Yes. Entering EV mileage adds estimated charging demand. Actual benefit depends on whether charging happens during solar generation or an off-peak window.
Can a battery charge overnight on a cheap tariff?
A compatible battery inverter/charger and tariff can make this possible. The result depends on the price spread, efficiency, charging hours and supplier terms.
Does the estimate replace an installer or electrical design?
No. Roof structure, shading, cable sizing, protection, product compatibility, DNO requirements and final electrical design require competent professional assessment.
Start with your own assumptions
See what system fits your home
Enter your postcode, electricity use and roof information. Compare the result before requesting quotations or buying components.