EV Charging Bolt-Ons and Add-On Rates

An EV charging bolt-on does one specific job: it leaves your household tariff exactly as it is and applies a cheaper rate only to the electricity your car uses. The Energy Ombudsman describes these products as add-on EV tariffs, where "consumers keep their existing household tariff but receive separate EV charging discounts, credits or other benefits"¹. That is the whole idea. You do not move your home to a time-of-use tariff, you do not change when the washing machine runs, and you do not have to give up a fixed deal you are happy with. Only the car's charging is treated differently.

The rates are the attraction. Independent guidance puts home EV charging at 7p per kWh on an off-peak or EV rate, against 24p per kWh for standard home charging, working out at about 2p per mile on an average tested EV efficiency of 3.18 miles per kWh². Good Energy's EV Charge bolt-on charges 8p per kWh overnight³. Against a public rapid charger at 65p per kWh⁴, the gap is large enough that where a household charges decides most of what it pays to run the car.

The way an add-on works alongside your current tariff

There are two broad ways to get cheaper car charging at home. The first is a full EV or time-of-use tariff, where the whole house moves to a tariff with cheap and expensive periods. The second is the bolt-on, sometimes called a Type of Use tariff or an add-on, and it works the other way round. Zapmap describes Type of Use tariffs as "add-ons to your existing energy tariff", requiring "a compatible home charger and a working smart meter", and offering "cheaper rates just for the specific energy used to charge your EV"⁵.

That last point matters more than it first appears. On some bolt-ons the cheaper kWh cost applies any time of day or night, not just in a fixed overnight window⁵. The tariff does not reward you for charging at 2am; it rewards you for charging through the right charger. The supplier, or its charging partner, can see which electricity went to the car because the charger reports it, and that share of your usage is billed or credited at the bolt-on rate while everything else stays on your existing prices.

This structure has real advantages for a household that does not want to reorganise its energy around a car:

• Your existing tariff keeps running. If you are on a good fixed deal, it stays.
• The household side stays free to change. A heat pump tariff or a solar export tariff can be pursued independently of the car side.
• No reorganisation of daily life. The washing machine can run whenever it always did.

The trade-off is dependence on two things: a smart meter that can record when the charging happened, and a charger and app that can prove it. Lose either, and the bolt-on cannot identify your charging kWh, so the cheap rate stops applying.

Off-peak rates: 7p to 10p per kWh across the market

The headline rates for cheap home charging cluster tightly, and the table shows where the main figures sit:

Why the spread? Partly it reflects what each product is. A bolt-on that only discounts car charging can go lower than a whole-house time-of-use tariff, because the supplier is only exposing a small slice of your usage to the cheap rate. Partly it reflects timing: rates are set against the general level of electricity prices, which moves each quarter with the price cap, so a rate published in one quarter may not match a rival's published months later. Treat any figure you see as a snapshot with a date on it.

The comparison that decides whether a bolt-on is worth having is not with other EV rates but with your own standard rate. At 24p per kWh standard against 7p per kWh off-peak, the car's electricity costs roughly a third of what it would on the household rate². Public charging closes none of that gap: a 50 to 149kW FOR EV charge point costs 65p per kWh⁴, roughly ten times the home off-peak rate, which is why households that can charge at home mostly do.

Good Energy EV Charge: 8p/kWh between midnight and 5am

Good Energy's EV Charge is the clearest current example of the bolt-on structure. The supplier states the rate plainly: "Charge your car for just 8p/kWh, that's less than 2.31p per mile"³. The cheap window is five hours, from midnight to 5am³. Unlike a whole-house tariff, this rate applies to the car's charging rather than to everything in the home, so the rest of the household's electricity stays on whatever tariff it is on.

Good Energy's own cost-per-mile figure comes with a stated basis:

That is a useful illustration of how a five-hour window works in practice. A charge spread over 8.8 hours implies a slower charge rate than the charger's maximum, which is exactly what a smart charger does when it spreads charging across the available window to hit a departure time. The car does not need to gulp electricity at full speed; it needs to be full by morning.

Two things follow for a household weighing this product. First, the per-mile figure depends on the car's efficiency, so a less efficient vehicle will cost more per mile even at the same 8p per kWh. Second, the midnight-to-5am window is fixed, so the charger must be able to schedule within it; a car plugged in at 6pm that starts charging immediately will burn household-rate electricity until midnight unless the charger holds it back. That scheduling is what the Ohme app, covered later on this page, exists to do.

The cost of charging fully on a bolt-on rate

The arithmetic of a full charge is simple once the rate is known. At 7p per kWh, a typical car's battery costs a fraction of what the same charge would at the 24p standard home rate². Good Energy's worked example gives the shape of it: a full overnight charge for a few pounds, not the tens of pounds a public rapid charger would charge³. Against 65p per kWh on a public 50 to 149kW point⁴, home charging on a bolt-on is roughly a tenth of the price per unit.

The cost of getting there is the other half of the sum:

• A 7kW home charge point: typically £700 to £1,200 fully installed⁷
• Installation in charger-and-tariff bundles: typically £500 to £1,000 per charger⁸
• An additional off-site charging cable: approximately £145⁹

None of that is covered by a bolt-on tariff; the tariff only changes the price of the electricity. Grants can offset some of it for eligible households, and the Workplace Charging Scheme covers up to 75% of purchase and installation costs including VAT, capped at £500 per socket, though that is an employer scheme¹⁰.

For the household budget, the honest framing is this: the bolt-on cuts the running cost of the car sharply, but the charger is the upfront investment, and the payback period depends on how many miles the household drives. A car doing high mileage on cheap home charging recovers the charger cost faster than one used occasionally. The electricity itself, at 7p to 8p per kWh, is close to the cheapest motoring energy available anywhere in the UK².

Who can switch and the smart meter requirement

The smart meter is the gatekeeper. The Energy Ombudsman states the position directly: "You don't need a smart meter simply to charge an EV, but without one you may not be able to access some EV-specific tariffs"¹. Smart Energy GB is firmer about the general case: "In most cases, a smart meter is required to access EV tariffs"¹¹. The reason is mechanical. A bolt-on has to identify which kWh went to the car and when, and that needs a meter recording usage in fine detail, working in smart mode.

Who can get the meter is itself conditional:

• Only the person paying the bills can request a smart meter installation from their energy supplier¹².
• Eligibility may vary, and Smart Energy GB's guidance excludes Northern Ireland, where the metering rollout is separate¹³.
• Renters are not excluded: Smart Energy GB publishes specific guidance for renting households, and eligibility may vary by property¹⁴.
• If a meter upgrade is needed, it must be arranged through the electricity supplier, not the local network operator¹⁵.

Beyond the meter, the charger matters. New EV chargers must be smart, able to be set to charge when there is less demand on the grid or more renewable electricity is available¹⁶. A bolt-on needs a charger that can talk to the supplier or its partner, so an older dumb chargepoint will not qualify. Households chasing installation grants face further conditions: flat owners and renters must use or own a vehicle on the approved list and use an approved installer¹⁷. None of this is onerous for a typical owner-occupier with off-street parking, but each condition is a place where an application can stall.

Using the Ohme app to schedule charging

A bolt-on rate is only worth what the charger does with it. If the cheap window is midnight to 5am and the car is plugged in at 7pm, something has to decide when the electricity actually flows. That is the Ohme app's job. Ohme describes its smart chargers as helping with "shifting EV charging away from the 5-8pm energy demand peak"¹⁸, which is both the grid's interest and the household's, since the evening peak is when standard rates are at their most expensive.

The app's core scheduling features are built around this. You can "start, stop & schedule charging sessions with one-off schedules for desired charge and departure time"¹⁹. You tell it how much charge you want and when you need the car, and it fits the charging into the cheap window. The usage centre lets you "track your smart charging, CO2, and solar savings" and keep "an eye on your car charging costs and every kWh used"²⁰. The app also keeps "a detailed history of each charging session and estimated costs based on your energy tariff"²⁰.

Two features deserve a mention because they change how the charger behaves. Max charge mode "overrides Ohme's smart charging features to let the car charge at maximum speed until full"²⁰, which is the right choice when you need range fast and the wrong one for a cheap overnight charge. The Approve plug-in feature lets you "authorise only trusted users to initiate charging sessions", and the app can require approval before charging, lock the front buttons and turn off the indicator lights and screen²⁰. For households with more than one car, the multicar feature lets you save, select and switch between vehicles, with sessions and savings in one place²¹.

Choosing listed or custom settings for your tariff in the Ohme app

The scheduling only works if the app knows what your tariff charges. Ohme's product pages describe "easy energy tariffs integration": you "connect your charger to your electricity tariff and let Ohme automatically schedule your EV to charge during off-peak hours"¹⁹. Where your supplier's tariff is one Ohme already knows, you select it from a list and the cheap windows are set for you. Where it is not, the app supports a custom tariff, where you enter the rates and the hours yourself, and the charger schedules against what you have entered.

The price cap setting is the other half of the setup. Ohme's guidance says you "can also set a price cap to ensure Ohme only charges at the cheapest times, to unlock savings on your energy bills"²⁰. On a bolt-on this matters in a particular way: if the cheap rate applies only to the car's charging, the cap should be set so the charger treats the bolt-on rate as the ceiling, not the household rate. A cap set at the household rate will let the charger schedule charging at times that cost you 24p rather than 8p.

Pairing the charger to the app is the first step, and Ohme's support pages cover it directly. The charger's serial number is on a white sticker underneath the unit, a 12 digit code beginning "ohme", and it can also be found on the Advanced Settings page in the app²². If the charger goes offline, the Ohme widget shows an alert; most of the time it reconnects automatically within about an hour, and if it is still offline when you are ready to charge, Ohme recommends power cycling it. The charger must be online before plugging in for settings and preferences to apply correctly²³. Without the app at all, the charger is not linked to an account and operates in plug and charge mode, charging instantly until full or unplugged, following settings configured in the car²⁰.

Charger compatibility plus solar charging and earthing

A bolt-on does not have to be the only cheap electricity in the house. Ohme states its home chargers are "solar charging compatible"¹⁸, and its product pages describe capabilities running "from multi-car control to smart tariff switching and solar integration"¹⁹. For a household with panels, the practical effect is that the charger can be set to prefer the home's own generation, with the bolt-on rate covering what the panels cannot supply. The app tracks solar savings alongside charging costs in the usage centre²⁰.

Compatibility is the condition to check before signing up to anything. A bolt-on needs a charger the supplier or its partner can work with, and Ohme's own guidance on setting up supplier tariffs shows how specific these pairings are, with dedicated setup paths for individual supplier products²¹. A charger from one ecosystem may not be able to report charging to a different supplier's bolt-on, in which case the cheap rate cannot be applied no matter how cheap it looks. The question to ask before switching is not just "what is the rate" but "does my charger work with it".

Installation standards sit behind all of this. A home charger is a fixed electrical installation, a permanent, high-load addition to a household circuit, and earthing arrangements are part of what a qualified installer assesses. A bolt-on tariff changes nothing about the electrical safety of the installation, but a charger moved or refitted when changing supplier should be rechecked by someone qualified. The charger's compatibility with the tariff is a software question; its safety is an installation question, and only the second one is non-negotiable.

Exit fees, fixed terms and the role of the price cap

Because a bolt-on sits on top of your existing tariff, the contract questions come in two layers. The household tariff keeps its own terms: fixed tariffs usually run 12 to 24 months²⁴, and exit fees "only apply to fixed-term deals (including some tracker tariffs), and cannot be charged in the last 49 days of" the term²⁵. Citizens Advice adds that a supplier may charge a fee to switch if your contract ends within the next 7 weeks²⁶. The bolt-on itself may have its own term and its own exit conditions, and those are worth reading before signing up, because the two layers do not always end together.

The price cap sits underneath everything. Ofgem's cap levels for 1 July to 30 September 2026 show, for the South East, a standing charge of £189.27 and an annual bill of £824.22 at 2,500 kWh on a single-rate meter, and £190.23 standing charge with £996.63 at 3,400 kWh on a multi-rate arrangement²⁷. The standing charge cap for electricity is 60.97p per day²⁸. The cap applies to default and standard variable tariffs, so a bolt-on's rate is set by the supplier against that backdrop rather than capped itself: the cheap car rate is a commercial price, not a protected one, and it can change when the supplier changes it.

What this means in practice is that a bolt-on's price is only as durable as the supplier's terms say it is. A rate quoted today reflects today's cap level and today's wholesale costs. The household side of the bill, the standing charge and the standard unit rate, continues to be governed by the cap if you are on a default tariff, and by your fixed terms if you are not. Switching itself is quick: moving to any energy tariff is simple, causes no power outages and typically takes just a few days²⁵.

Warranty, disconnection and your home move

A bolt-on is tied to a charger, and a charger is tied to a wall, so moving house breaks the arrangement in ways a normal tariff switch does not. The official grant rules give a hint of the wider picture: households applying for the chargepoint grant for renters or flat owners are ineligible if "you're moving house or planning on moving"¹⁷. The same logic applies to charger-and-tariff bundles generally, where the product assumes a stable home and a stable installation.

The charger itself can move, but not for free. A wallbox is a fixed electrical installation, so taking it to a new home means a qualified uninstall and a qualified reinstall, and the new installation has to suit the new property's supply and earthing. The warranty question is worth checking with the manufacturer before planning it, since terms differ. What does survive, Ohme states, is your data: "Your preferences, settings, and charging history will stay saved in your account, so you can easily pair a new charger later"²².

For the next owner, the position is that a charger left behind is theirs, but your tariff and your app account are not. The charger will need pairing to the new owner's account, and its serial number, on the white sticker underneath the unit, is the starting point for that²². Your own account can be closed or reused at the new property. Northern Ireland households should note that the grant landscape differs, with separate infrastructure and chargepoint grant arrangements administered there¹⁰. The bolt-on itself ends where the home ends, and starts again only when a charger, a meter and a tariff are re-matched at the new address.

How far a bolt-on goes towards energy independence

A bolt-on is a modest but real gain for household energy independence. It lets a home run its car on electricity priced at 7p to 8p per kWh instead of 24p², which weakens the pull of public charging networks and their 65p per kWh rapid rates⁴. It does not require the household to reorganise its energy use, and it leaves the rest of the home free to pursue other independence measures, whether that is a solar export tariff or a heat pump rate, because the household tariff is untouched¹.

The dependencies that remain are worth naming plainly:

• A smart meter working in smart mode, without which the bolt-on cannot identify the car's charging¹.
• A compatible charger, able to report charging to the supplier or its partner⁵.
• An app that stays connected; if the charger goes offline and stays that way, the scheduling that captures the cheap window stops working²³.
• A supplier-set rate, which can change, since bolt-on rates sit outside the price cap's protection²⁷.
• The manufacturer's app and systems, which must continue to exist and be supported for the smart features to work²⁰.
• Imported electricity: a bolt-on makes imported electricity cheaper, it does not make any of it.

Set against that, the structure is honest about what it is. It is not a whole-house commitment, it is not a lock-in of the household tariff, and the data, settings and history that make it work stay with the household's own account²². For a home that wants the car's fuel bill cut to a few pounds a week without re-engineering the rest of its energy, that is a reasonable bargain, provided the meter, the charger and the app all keep doing their jobs.