Car at home during the day
Direct solar EV charging can work extremely well because the car provides a huge battery ready to absorb surplus generation.
Electric vehicles and solar explained
Is solar worth it if I have an electric vehicle?
An electric car can become one of the largest electrical loads in a home. Drive enough miles and it can add thousands of kilowatt-hours to annual electricity consumption.
That can make additional solar panels extremely useful — but the smartest strategy is not always simply “put every spare solar unit into the car”.
The short answer
Yes — an EV can make a larger solar system considerably easier to justify.
Solar becomes financially useful when the electricity it generates has somewhere valuable to go.
An electric vehicle creates a potentially enormous new destination for that electricity.
Depending on mileage, an EV can add several thousand kilowatt-hours to annual household demand.
More annual demand can justify more solar generation.
More solar can reduce the electricity bought for driving.
A smart charger can shift charging into cheaper periods.
A home battery can shift electricity between different parts of the day.
An EV tariff can completely change the best charging strategy.
The car, solar array, home battery and tariff should be designed as one energy system.
Treating each component as an unrelated purchase can leave a technically impressive installation behaving very inefficiently.
Start with the mileage
How much electricity does the EV actually add?
Electric-car efficiency varies substantially with the vehicle, temperature, speed, tyres, heating, driving style and journey type.
For a simple homeowner calculation we can use an illustrative figure of 4 miles per kWh.
That is not a promise that every vehicle will achieve 4 miles/kWh. Some will do better and some considerably worse, especially in cold weather.
Annual mileage ÷ real-world miles per kWh = approximate annual driving energy
Example: 10,000 miles per year
10,000
Annual miles driven
4 mi/kWh
Illustrative vehicle efficiency
2,500 kWh
Approximate energy used for driving
>2,500 kWh
Electricity drawn from the wall once charging losses are included
10,000 miles ÷ 4 miles/kWh = approximately 2,500 kWh
So a household that previously used 3,500 kWh per year could move to more than 6,000 kWh of annual electricity demand once regular home EV charging is included.
Solar sizing
This is why an EV can justify significantly more panels.
Imagine the property needed approximately another 2,500 kWh of electricity each year because of the car.
If a particular roof design was expected to produce roughly 350–400 kWh per year from each modern panel, then approximately six to eight additional panels could generate a similar amount of annual energy.
That does not mean those panels directly cover every EV charge.
Annual energy balance and instantaneous power are different. The car may be away when the panels are generating and plugged in when the sun has gone down.
But it demonstrates why designing the solar array around the home's old pre-EV electricity bill can materially understate future demand.
Solar-powered driving
One kilowatt-hour of solar can represent several miles of driving.
Using our simple illustrative efficiency of 4 miles/kWh:
1 kWh of electricity ≈ 4 miles of driving
So 10 kWh of surplus solar delivered into the car could represent roughly 40 miles of theoretical driving energy before allowing for charging losses and real-world variation.
That is one reason EV ownership can substantially increase the value of solar generation that might otherwise have been exported.
The timing problem
The solar panels cannot charge a car that is sitting at work.
This sounds obvious, but it is central to the design.
A homeowner may leave for work at 7:30am and return at 6pm.
The strongest solar generation may have happened while the car was twenty miles away.
Car away during the day
A home battery, export tariff or different charging strategy becomes more important because the EV cannot receive the midday surplus directly.
A 7kW charger
Does a 7kW charger need 7kW of solar?
No.
The 7kW figure is approximately the maximum charging power of a normal domestic single-phase charger.
A suitable solar-aware charger can vary the current supplied to the vehicle according to available surplus generation.
If the solar system has only 3kW spare, the charger does not necessarily need to draw the full 7kW.
It may reduce the vehicle's charging rate instead.
Maximum charger power and actual charging power are not the same thing.
A 7kW charger can spend much of its life charging at less than 7kW.
There is a minimum too
Small amounts of solar surplus may not be enough to keep the car charging.
Normal AC EV charging has a minimum charging current.
On a single phase this is typically around 6 amps, or approximately 1.4kW at nominal UK voltage.
If only 700W of surplus solar exists, a charger cannot simply command most vehicles to charge continuously at 700W.
Depending on the charger configuration it may:
pause until enough surplus exists;
draw the missing electricity from the grid;
or blend renewable and grid electricity according to the user's settings.
This matters on smaller solar systems and cloudy days.
A larger PV array can spend more time above the minimum power needed for useful surplus-only vehicle charging.
But here is the clever bit
Charging the EV directly from solar is not always the cheapest option.
Suppose, purely as an illustration:
Your export tariff pays 15p/kWh for surplus solar.
Your overnight EV tariff lets you buy electricity for 7p/kWh.
If you divert one solar kWh into the car, you avoid buying a 7p overnight unit — but you also give up 15p of export income.
Export solar for 15p → buy EV electricity later for 7p = 8p gross difference
In that simplified example, exporting the solar and charging the car overnight could be financially better.
Real tariff conditions, charging losses and rate windows still need to be included.
This changes the usual solar advice
“Use as much of your own solar as possible” is no longer always the full answer.
| Situation | Potentially sensible strategy |
|---|---|
| Poor export rate | Using surplus solar directly in the EV may be very valuable. |
| High export rate + very cheap overnight EV rate | Exporting solar and charging overnight may produce a better financial result. |
| Car at home during sunny periods | Solar-aware charging can absorb surplus dynamically. |
| Car away every weekday | Home battery storage or export may capture more value from daytime generation. |
| Long journey tomorrow | Ensuring the EV reaches the required state of charge is more important than perfect tariff optimisation. |
Home battery or EV?
Which one should receive the spare solar first?
There is no universal answer.
An EV battery might hold 50, 70 or even 100 kWh.
A home battery may hold only a fraction of that.
But the home battery has one major advantage:
It normally stays at home.
So the correct priority depends on what the household needs.
Three different strategies
The energy-management priority can change from one household to another.
Prioritise the EV
This may make sense when the car is at home, needs significant charge and the homeowner wants to minimise purchased driving energy.
Prioritise the home battery
This may make sense where evening household electricity is expensive and the EV can be charged very cheaply overnight.
Prioritise export
This can be rational where the export rate exceeds the cost of buying replacement electricity during a cheap charging period.
Let software optimise it
Increasingly sophisticated chargers, batteries and energy management systems can schedule energy according to generation, prices and required EV charge levels.
Smart charging
Modern home EV charging is increasingly about software as much as electrical power.
Private EV chargers sold for domestic use in Great Britain are subject to smart-chargepoint regulations.
Among other requirements, compliant chargers include smart functionality allowing charging to respond to timing or external signals.
This helps charging move into periods when:
electricity prices are lower;
grid demand is lower;
or renewable electricity is more readily available.
The charger should also allow the owner to override smart scheduling when immediate charging is required.
A very important buying decision
“Smart charger” does not mean “compatible with every smart EV tariff”.
This distinction catches people out.
A charger can comply perfectly well with UK smart-chargepoint regulations and still not integrate with a particular supplier's managed EV tariff.
Some tariffs control:
the charger itself;
the vehicle directly;
or only specified combinations of charger and vehicle.
Check tariff compatibility before choosing the charger.
Do not spend hundreds of pounds installing a charger and only then discover that the electricity tariff you wanted cannot control it. Supplier compatibility lists can change, so check the current list before installation.
Connectivity matters too
A smart charger needs reliable communication if you want the clever features.
Smart tariffs, app control, charge scheduling and remote energy management depend on communication.
Depending on the charger this may use:
home Wi-Fi;
Ethernet;
mobile/cellular connectivity;
or another communication gateway.
UK smart-chargepoint rules include provisions intended to allow ordinary charging to continue if communications are lost.
But losing communication can still interfere with the smart features that made the charger attractive in the first place.
Check the signal where the charger will actually be installed.
Good connectivity at the kitchen table does not prove good connectivity at a detached garage or outside wall.
A high-demand example
An EV can turn a modest electricity user into a high-consumption household.
Illustrative annual demand
3,500 kWh
Existing household electricity
2,500+ kWh
Approximate EV charging requirement
6,000+ kWh
New combined electricity demand
+71%+
Increase versus the old household demand
And that is for one illustrative EV.
A household with two electric cars, high annual mileage, a heat pump and electric hot water can become an entirely different energy proposition.
Design for the house it is becoming — not merely the historical electricity bill.
Planned electrification belongs in the solar calculation from the start.
Two EVs
Multiple electric cars make inverter, supply and charging strategy increasingly important.
Two 7kW chargers do not necessarily need to draw 14kW simultaneously.
Load management can distribute available power between chargers and other household equipment.
But a property containing:
a large solar array;
a high-power hybrid inverter;
substantial home battery storage;
two EV chargers;
and perhaps a heat pump
deserves a proper whole-property electrical assessment.
Do I need three phase?
Not for an ordinary 7kW home charger — but it can become relevant at higher power.
Most familiar domestic chargers are single phase and around 7kW.
Three-phase installations can support higher AC charging power such as approximately 11kW or 22kW where:
the property has three-phase electricity;
the charger supports it;
the vehicle's onboard charger supports it;
and the DNO connection has sufficient capacity.
Faster charger does not guarantee faster charging.
The car's onboard AC charger ultimately limits how quickly it can accept AC electricity.
See our separate guide: Should I upgrade my home to three-phase electricity?
The DNO
EV charging also affects the local electricity connection.
A home charger is a significant electrical load.
The local Distribution Network Operator needs visibility of new EV charging installations and the installer normally deals with the relevant notification process.
Additional investigation may be needed where there are concerns about:
the size of the incoming service;
the main cut-out fuse;
existing high electrical demand;
a looped electricity supply;
multiple chargers;
or other major low-carbon technologies.
If you are unsure what a looped supply means, see: What is a looped electricity supply?
What about V2H and V2G?
Eventually the enormous battery in the car may become part of the house.
Bidirectional charging allows electricity to flow both into and out of an electric vehicle.
This creates possibilities including:
Vehicle-to-home: using EV energy to support household demand.
Vehicle-to-grid: exporting EV energy into the electricity network.
An EV battery can be many times larger than a normal home battery, so the potential is enormous.
Do not design today's system assuming every EV can do this.
Bidirectional capability is not yet universal. The vehicle, charger, controls, tariff and grid-connection arrangement all need to support it.
The future
Cars are likely to become active parts of the electricity system.
Government energy policy is increasingly looking at EV smart charging and bidirectional vehicle-to-everything technology as sources of flexibility for the electricity network.
In future, millions of parked EVs could potentially:
charge when renewable electricity is plentiful;
reduce charging during periods of grid stress;
and in compatible systems return electricity when it is valuable.
That makes charger interoperability and good system design increasingly important.
Before choosing the solar system
I would want answers to these questions.
1. How many miles will the EV travel each year?
Annual mileage is the starting point for estimating charging demand.
Annual mileage is the starting point for estimating charging demand.
2. What real-world efficiency does that vehicle achieve?
Do not assume every EV delivers the same miles per kWh.
Do not assume every EV delivers the same miles per kWh.
3. When is the car normally parked at home?
This determines how much direct solar charging is realistically possible.
This determines how much direct solar charging is realistically possible.
4. What electricity tariff will be used?
Cheap overnight charging can completely change the economics.
Cheap overnight charging can completely change the economics.
5. What is the export rate?
Sometimes exporting solar and buying cheap electricity later is the better trade.
Sometimes exporting solar and buying cheap electricity later is the better trade.
6. Is the charger compatible with the intended tariff?
Smart does not automatically mean compatible with every supplier.
Smart does not automatically mean compatible with every supplier.
7. Can the charger follow solar surplus?
If daytime solar charging matters, this feature should be checked specifically.
If daytime solar charging matters, this feature should be checked specifically.
8. Is home battery storage planned?
The battery and EV should not accidentally fight each other for the same solar energy.
The battery and EV should not accidentally fight each other for the same solar energy.
9. Is a second EV likely?
Future vehicle demand may justify designing additional electrical capacity now.
Future vehicle demand may justify designing additional electrical capacity now.
10. What can the property's electrical supply support?
Charger load, solar, batteries and other large appliances must work together safely.
Charger load, solar, batteries and other large appliances must work together safely.
Evidence behind the proposal
A good solar design should show the EV calculation rather than simply adding panels.
If an installer says the EV means you need a larger solar system, ask them to show why.
The calculation should be understandable.
Annual mileage assumption
Vehicle efficiency assumption
Estimated annual EV electricity demand
Existing household electricity consumption
Expected solar generation
Self-consumption assumption
Battery behaviour
Import tariff
Export tariff
More panels should follow from more demand — not from the salesperson wanting a larger order.
Equally, ignoring thousands of kilowatt-hours of foreseeable EV demand can leave a customer with a system that was undersized from the day it was installed.
One whole energy system
The best result comes from making all the technologies cooperate.
Solar
Generates the low-cost electricity available to the property.
Home battery
Moves electricity from one part of the day to another and can exploit cheap tariffs.
EV
Creates a large, flexible electricity demand that can often be moved to favourable times.
Smart charger
Controls when and how quickly the vehicle receives electricity.
Tariff
Determines whether consuming, storing, importing or exporting each kWh creates the greatest value.
Energy management
Decides how the available generation and storage should be prioritised.
The cleverest solar system is not necessarily the one that uses the
most solar electricity itself. It is the one that creates the best
overall energy result for the household.
Frequently asked questions
Solar and electric vehicles answered.
Is solar worth installing if I have an electric vehicle?
Often yes. An EV can materially increase annual household electricity demand, creating much more opportunity for a suitably sized solar system to reduce imported electricity.
How much electricity does an EV use each year?
It depends on mileage and vehicle efficiency. At an illustrative 4 miles/kWh, 10,000 miles requires roughly 2,500kWh of driving energy before charging losses are considered.
Should I install more panels because I have an EV?
Potentially. Expected EV electricity demand should be added to existing household consumption before deciding how much PV is appropriate.
Can solar charge my EV directly?
Yes. A compatible solar-aware charger can vary vehicle charging according to available surplus generation.
Does a 7kW charger need 7kW of solar?
No. Seven kilowatts is approximately the maximum charging power. Smart charging can operate below that level where the charger and vehicle support it.
What is the minimum solar needed for EV charging?
Normal single-phase AC charging generally requires around 6 amps, approximately 1.4kW. Below that, a solar-aware charger may pause or supplement the solar with grid electricity.
Is solar always cheaper than overnight EV charging?
No. If your export rate is higher than your overnight import rate, exporting solar and buying cheap electricity later may be financially better.
Do I need a home battery as well?
Not necessarily. It becomes more useful where the car is away during sunny periods, evening household demand is high or cheap grid electricity can be stored for later use.
Should the EV or home battery charge first?
It depends on driving requirements, evening demand, import prices and export rates. There is no single priority that is correct for every household.
Are all smart chargers compatible with every EV tariff?
No. Supplier eligibility varies by vehicle and charger, so current compatibility should be confirmed before installation.
Can my EV battery power my house?
Some compatible bidirectional systems can support vehicle-to-home operation, but the technology is not yet universally supported by vehicles, chargers or tariffs.
Does my EV charger need to be reported to the DNO?
Domestic installations are normally notified to the local DNO, typically by the installer. Some properties require additional network assessment.
Official guidance checked
EV charging is changing quickly.
This guide was reviewed against current material available in August 2026 including:
- Energy Saving Trust — Charging Electric Vehicles.
- Energy Saving Trust — Battery Storage.
- UK Government — Electric Vehicles Smart Charge Points Regulations guidance.
- Office for Zero Emission Vehicles — residential chargepoint specifications.
- Vehicle Certification Agency — electric vehicle energy-consumption guidance.
- UK Government — Clean Flexibility Roadmap and V2X development.
- Energy Networks Association — EV connection and generation requirements.
Vehicle efficiency, charger compatibility and electricity tariffs change over time. The current vehicle specification, charger documentation, supplier eligibility rules and DNO requirements take precedence over the illustrative examples in this homeowner guide.
Related Tom Solar guides
Understand the rest of the home energy system.
Tom Solar view
An electric car is one of the strongest reasons to reconsider the size of a solar system.
An EV can materially change the annual electricity consumption of a home.
Designing solar around the household's historic electricity bill while ignoring thousands of miles of future electric driving can leave the system unnecessarily small.
But simply covering the roof and telling the customer to charge the car whenever the sun shines is not sophisticated enough either.
The real design should consider:
how far the car travels;
when it is parked at home;
how much the PV array generates;
what the home battery is expected to do;
what the export tariff pays;
what overnight charging costs;
and whether all the equipment can communicate properly.
Do not merely install solar panels beside an EV charger.
Design the house, solar, battery, tariff and car as one connected energy system.