An electric car is the largest flexible load most households will ever own, and getting the charging right is worth more than almost any other energy decision. Done well, charging at home is cheaper per kilometre than anything else available. Done badly, it trips fuses, costs peak-rate money and occasionally requires an expensive supply upgrade that was avoidable.
Here is what matters, in the order it matters.
How much power you actually need
The instinct is to buy the fastest charger available. It is usually the wrong instinct.
A single-phase 7 kW charger adds roughly 30 to 40 km of range per hour. Over a ten-hour overnight window that is 300 to 400 km — considerably more than most people drive in several days.
An 11 kW three-phase charger requires a three-phase supply, which is normal in the Netherlands, Germany and much of continental Europe and unusual in UK housing.
A 22 kW charger needs three-phase supply and a car that can accept it, and most cars cannot — onboard alternating-current chargers are commonly limited to 7.4 or 11 kW. Buying 22 kW for a car limited to 11 achieves nothing at all.
Check your car's onboard AC charging limit before specifying anything. It is the ceiling, regardless of what you install.
And consider the opposite direction: a slower charge is gentler and gives a longer window in which to follow cheap prices, which matters on an hourly tariff.
The supply constraint, which stops projects
This is the practical issue people meet late and should meet early.
Your property has a maximum supply capacity set by the main fuse. A charger at 7 kW is roughly 32 amps on single phase, which is a large fraction of a modest domestic supply. Add an electric shower, an oven and a hob and you can exceed it.
Three responses, in increasing order of cost:
Load balancing. A current sensor on the incoming supply lets the charger reduce its draw when the rest of the house is busy, and increase it again afterwards. This is the right answer for almost every installation, it is inexpensive, and it should be specified as standard rather than as an upgrade. Note that it must measure the whole house, not just the charger circuit.
Sequencing. Not running the car and other large loads at the same time, which automation handles invisibly.
A supply upgrade. An application to your network operator, possibly involving work in the street, potentially expensive and slow, and in constrained areas sometimes refused or delayed.
Establish your main fuse rating before ordering, and if you also intend to fit a heat pump, plan both together. Discovering the constraint after the second installation is an expensive sequence to unwind.
Tariffs, which is where the money is
Charging is the clearest case for a time-varying tariff in domestic energy, because you have a large load whose timing genuinely does not matter.
A time-of-use tariff with a cheap overnight rate plus a simple timer captures most of the available saving with no complexity. For many households this is the right answer and the end of the story.
An hourly dynamic tariff can do better, because you can charge in the cheapest few hours rather than across a whole window — but it needs automation that follows prices, and it carries exposure to price spikes.
Charging on solar surplus is satisfying and only useful when the car is home in daylight. For a commuter that means weekends, and for someone working from home it can be a large share of their charging.
Two practical points. Set the charging deadline rather than the start time — “full by 7am” lets a controller pick the cheapest hours, whereas “start at midnight” does not. And do not schedule from both the car and the charger, which is a classic conflict producing a car that never charges: pick one and disable the other.
Battery care, briefly and without alarm
Modern battery packs are managed by the car and are considerably more robust than early anxiety suggested. A few habits are still worth having.
Charge to around 80 per cent for daily use, and to 100 per cent when you need the range. Most manufacturers now say this explicitly, and most cars let you set a limit.
Avoid leaving it sitting at a very high or very low state of charge for long periods, particularly in heat.
Slow alternating-current charging is gentler than repeated rapid direct-current charging, which is another argument against over-specifying home power.
Precondition while plugged in in winter. Warming the cabin and the battery from the wall rather than the pack preserves range and is more efficient overall.
Follow your own manufacturer's guidance over any general advice, including ours — recommendations differ meaningfully between chemistries, and some packs are specifically designed to be charged to 100 per cent regularly.
What to look for in a charger
Load balancing included, measuring the whole house.
Local control. A charger that requires an internet connection and a manufacturer's cloud to start charging is a charger that will occasionally leave you with an empty car. Ask specifically what happens with no connection, and prefer one that can be scheduled locally or driven by your own hub.
An open interface or established integration, so your own system can implement tariff logic rather than depending on the manufacturer's app being clever.
Solar surplus support, if you have panels, with genuinely proportional modulation rather than crude on-off switching — and check the minimum charging current, since most cars will not accept below about 6 amps, which sets a floor on how little surplus is usable.
Energy metering, ideally to a standard suitable for reimbursement if you charge a company car.
A tethered or untethered cable, which is preference: tethered is convenient, untethered is tidier and lets you replace a damaged cable cheaply.
Weather and vandal resistance, and a sensible mounting position that does not require the cable to cross a public footpath.
Correct electrical protection, which is the installer's responsibility and worth confirming is documented.
Automations worth building
Charge to a deadline, not a schedule, letting the system choose the cheapest hours.
Throttle when the house is busy, which is load balancing doing its job.
Divert solar surplus above the minimum current the car accepts.
Stop at a state-of-charge limit for daily use, with an easy “full tonight” override before a long trip.
Precondition before departure, from a calendar or a habitual time, while still plugged in.
Notify on charge complete, and more usefully on charge not started — a car that failed to begin is the fault you want to hear about at 11pm, not 7am.
Alert if the cable is unplugged unexpectedly, if that is a concern where you park.
Log energy per session, which you will want for cost tracking and for any reimbursement.
A sensible plan
- Find your main fuse rating and your car's onboard AC limit.
- Specify 7 kW single phase unless you have three-phase supply and a car that can use it.
- Insist on whole-house load balancing.
- Get onto a time-varying tariff before worrying about anything clever.
- Choose a charger that works locally and can be driven by your own system.
- Set a deadline rather than a start time, and schedule in one place only.
- Add the charge-not-started alert.
- Plan a heat pump at the same time if one is coming.
Items three and six are the two that prevent the common failures: one stops the fuse tripping, the other stops the car sitting empty because two schedulers disagreed.