Vehicle to Grid EV Charger: How Used EVs Slash Payback
By Gordon Routledge
Sunday 7th September 2025
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The term game changer gets thrown around like confetti, but with vehicle to grid (V2G) it’s deserved, even if it still sounds gloriously bonkers.
Your EV is a battery on wheels. With a compatible car and the right charger, vehicle to grid (V2G) will run your home, support the grid, and might even boil the neighbour’s kettle.
As programmes and approvals land, that parked battery stops loafing and starts earning, time-shifting energy, boosting solar self-use, and getting paid for grid support.
So, why do I think it’s such a big deal? Let’s look at the numbers.
This morning I had a quick search on AutoTrader and found nearly 2,000 used electric vehicles for sale at under £10,000. One example? A 2020 Renault Zoe R135 advertised for £4,999. The seller assures us it was owned by a vicar’s wife, the classic dealer shorthand for “immaculately cared for.”
Except, in this case, it turns out the vicar’s wife must have been a very committed parishioner. In just a few years she’s clocked up 129,000 miles, no doubt ferrying sponge cakes and hymn books to every corner of the county. So yes, the car is “well used.”
But we’re not interested in the mileage. What really matters here is the battery.
When new, this Zoe came with a 52 kWh pack. Let’s be pessimistic and assume years of motorway miles, regular fast charging outside Greggs, and the occasional enthusiastic use of Eco-Off have reduced that to a usable ~43 kWh. Even at that worst-case level, you’re effectively getting ~43 kWh of battery storage for £4,999 — that’s about £116 per kWh.
For context, my own Tesla dropped from around 100 kWh to 95 kWh over five years and 80,000 miles — so that 43 kWh figure is probably a worst-case scenario rather than the norm.
Speaking of Tesla — let’s pit our bargain used EV against Elon’s finest home energy storage solution, the Tesla Powerwall 3. Boxt lists it fully installed at £14,900 for 27 kWh (about £552/kWh). Now let’s walk through a few real-world home energy scenarios and see what the numbers say.
ZAPTEC GO 2 -
Vehicle to Grid: How Much Could You Earn?
Scenario 1: Typical UK home.
Think of a household using about 2,700 kWh per year (about 7.4 kWh per day). Assume the EV can charge and discharge at 7 kW on single phase. Charge overnight at 7p/kWh, discharge when power is about 25p/kWh, and allow 5% round-trip loss (delivered cost about 7.37p/kWh). That arbitrage saves about £476 per year if you time-shift the full 2,700 kWh.
Keeping a 30% driving reserve on a 43 kWh used EV leaves a daily swing of 30.1 kWh. After covering the home’s 7.4 kWh per day, you still have about 22.7 kWh per day spare for export — 8,286 kWh per year, worth about £1,461 per year at the same net margin.
Totals: EV about £1,937 per year, giving about 2.6 years simple payback on £4,999.
For comparison, a 27 kWh wall battery (20% reserve gives 21.6 kWh per day swing) leaves about 14.2 kWh per day to export (5,184 kWh per year, about £914 per year). Add the same £476 per year arbitrage and you’re at about £1,390 per year — about 10.7 years payback on £14,900 installed.
Heat-pump home.
Replace the gas boiler with a heat pump and electric use rises to about 6,500 kWh per year (about 17.8 kWh per day). The same tariff shift lifts arbitrage to about £1,146 per year. With the 43 kWh EV and a 30% reserve, you still have about 12.3 kWh per day spare after serving the house — 4,490 kWh per year — worth about £791 per year.
Totals: EV about £1,937 per year, about 2.6 years payback.
Mind peak power as well as energy. Type 2 V2G is connector-limited: 7 kW single phase; 22 kW three phase. In our example the Renault hardware can do about 11 kW on three phase. Fixed batteries have their own continuous-output caps too. When hot-water reheat, the compressor and cooking collide, you may still import for peak power, even if the day’s energy balance is solid.
For the 27 kWh wall battery, there is only about 3.8 kWh per day left for export (1,387 kWh per year, about £244 per year). Add £1,146 per year arbitrage and you get about £1,390 per year, about 10.7 years payback.
Heat pump plus solar.
Add about 3,000 kWh per year of PV and assume most generation is stored for later via the battery with 5% loss. Delivered solar is about 2,850 kWh per year, avoiding about £712.50 per year of imports at 25p. The remaining grid energy is 6,500 − 2,850 = 3,650 kWh; time-shifting that at the established margin (about 17.63p/kWh) adds about £644 per year.
Base benefit (solar self-use plus shifting the remainder): about £1,356 per year.
With the 43 kWh EV (30% reserve), you still have about 12.3 kWh per day headroom for export — 4,490 kWh per year, worth about £612 per year.
Totals: EV about £1,968 per year, about 2.54 years payback on £4,999.
For the 27 kWh wall battery, export headroom falls to about 3.8 kWh per day (1,387 kWh per year, about £189 per year).
Totals: wall battery about £1,545 per year, about 9.70 years payback on £14,900.
Picture a typical UK home with a gas boiler and about 2,700 kWh per year of electricity use — roughly 7.4 kWh per day for lights, cooking and appliances. In a V2G set-up, assume the car charges at 7 kW on single phase and can discharge at the same 7 kW back into the house (or, where permitted, to the grid). You fill the battery overnight at 7p/kWh, then use or export when prices are around 25p/kWh, allowing a sensible 5% round-trip loss. That pricing trick is arbitrage: buy electricity when it’s cheap, then use or sell it when it’s dear.
On these numbers the delivered cost is about 7.37p/kWh, so each shifted kilowatt-hour avoids about 17.63p. Time-shift the home’s full 2,700 kWh per year and you save about £476 per year. At a 7 kW discharge rate, covering the 7.4 kWh daily shift takes just over an hour, leaving plenty of evening peak window for anything else.
Because the household draw you’re shifting averages about 7.4 kWh per day, a cautious 43 kWh used-EV battery (keeping 30% in reserve for driving) still leaves around 22.7 kWh per day spare for export — roughly 8,286 kWh per year. Valued at the same about 17.63p/kWh net margin, that export earns about £1,461 per year. Add the about £476 per year from arbitrage on your own consumption and the used-EV route totals about £1,937 per year, which gives a simple payback of about 2.6 years on a £4,999 car.
For comparison, a Tesla Powerwall 3 (27 kWh) treated the same way (keeping 20% in reserve for longevity/backup) has a daily swing of about 21.6 kWh. After covering the home’s 7.4 kWh per day shift, that leaves around 14.2 kWh per day to export — about 5,184 kWh per year — worth about £914 per year at the same margin. Add the about £476 per year household arbitrage and the Powerwall comes to about £1,390 per year, yielding a simple payback of about 10.7 years on a £14,900 installed system.
Bridging Residential and Commercial Charging
Summary:
| Home scenario | Used EV: savings | Used EV: payback | Powerwall 3: savings | Powerwall 3: payback |
|---|---|---|---|---|
| Typical (2,700 kWh/yr, gas) | ~£1,937 | ~2.6 yrs | ~£1,390 | ~10.7 yrs |
| Heat pump installed (6,500 kWh/yr) | ~£1,937 | ~2.6 yrs | ~£1,390 | ~10.7 yrs |
| Heat pump + solar (best) | ~£2,387 | ~2.09 yrs | ~£1,964 | ~7.63 yrs |
| Heat pump + solar (conservative) | ~£1,968 | ~2.54 yrs | ~£1,545 | ~9.70 yrs |
Future-Proofing with EV Blocks
Another highlight from the discussion was the contribution of Trevor Palmer, founder of EV Blocks, whose precast foundation system is designed specifically for EV chargers. These units enable much faster and more consistent installations by allowing groundwork to be completed in advance, with chargers simply mounted when required.
This approach also future-proofs sites. Developers can install the foundations early, then add chargers as demand grows. When technologies evolve, as they inevitably will — the chargers can be swapped or upgraded easily without disruptive or costly groundworks.
What started as a solution for residential and commercial installations has now evolved to support high-powered DC chargers as well. By following the market and adapting the product range, EV Blocks has positioned itself as a critical enabler of scalable charging infrastructure, giving both developers and installers the flexibility they need in a rapidly changing industry.
From Installer to Charge Point Manager
Costello’s EV also illustrates how installer businesses can evolve beyond fitting hardware. Having grown from residential installations into commercial projects, they now provide charge point management services, capturing long-term value through ongoing contracts.
In Wales, for example, they have partnered with local councils to deliver public EV charging solutions. Instead of simply supplying equipment, they offset some of the upfront cost in exchange for a profit share on charging revenue, alongside maintenance and support contracts. This creates recurring income while helping councils roll out more public chargers.
Of course, operating at this level means meeting the requirements of the UK Public Charge Point Regulations. These demand high equipment reliability, contactless payment options, and 24/7 customer support, including a Welsh-language helpline in Wales. It’s a nuanced but entrepreneurial approach that shows how installers can scale their business models.
Why OCPP and True Flexibility Matter
Long-term support for charging infrastructure depends on more than hardware. It also requires robust service integrations — from payment providers to app platforms. This is where the Open Charge Point Protocol (OCPP) is critical.
OCPP gives operators the freedom to choose how chargers connect to customer-facing apps, billing systems, or reimbursement platforms. It also provides protection if a provider ceases trading, since operators can switch systems without replacing hardware.
However, as highlighted during the stream, not all OCPP is created equal. Some manufacturers rely on cloud-based “virtual OCPP” services. With the UK’s tightening cyber security regulations, a number of these providers have already withdrawn from the market, taking their cloud services offline — leaving installed chargers unusable.
Rolec embeds OCPP directly within its chargers. This means that even in the unlikely event of Rolec itself ceasing operations, the chargers would continue to function. For operators and installers, that kind of resilience is invaluable.
Training, Culture, and Long-Term Partnerships
At first glance, some might wonder why Rolec has a dedicated role for training and culture. EV training is often assumed to be purely technical — and judging by Allan Ross’s performance on the Electricians Challenge, he’s clearly not there to lead the practical fitting demonstrations!
Instead, his role is about building the ecosystem that enables installers to succeed. The livestream made it clear that EV charging is built on partnership. End users want installers who can manage the whole process, and installers need manufacturers who will provide reliable products, responsive support, and adapt to a changing market.
Rolec has built a trusted installer network that receives ongoing training and benefits from being part of a wider community. Members can collaborate on larger projects or deliver warranty cover for existing installations.
This ecosystem is strengthened by the Rolec Connect app. Far beyond a commissioning tool, it supports installers from the initial enquiry and quotation right through to installation and aftercare. For many, it removes the need for a separate CRM system, making their businesses more efficient while keeping them closely connected to Rolec and its network.
Closing Thoughts: Building a Sustainable Future in EV Charging
The big takeaway from Rolec Unplugged? EV charging is no longer just about hardware. Success depends on the ecosystem — the relationships, flexibility, and support structures that surround the chargers themselves.
From new-build housing to fleet management, from future-proofing foundations with EV Blocks to entrepreneurial public charging models, and from OCPP resilience to Rolec’s investment in training and partnerships, the message is clear:
👉 EV charging isn’t a race to the bottom — it’s a dynamic industry full of opportunities for those ready to adapt.
For electricians and businesses willing to embrace this shift, the potential has never been greater.
