# V2L affordability calculator — the tool

> An honest model of whether running an essential-loads board off an EV's V2L output pays back, compared against a standalone home battery, a second-hand battery, smart cheap-rate charging, and doing nothing. The saving is the cheap rate AFTER round-trip losses, battery wear and equipment cost — and only if the car and charger can follow the schedule.

## The method, the formulas & the worked example

The full load-shifting method, the exact saving formulas and the founder worked example live on the explainer (canonical): https://v2lworkshop.co.uk/affordability/worked-example (plain-markdown copy at https://v2lworkshop.co.uk/md/affordability/worked-example). The EV-as-battery vs static-home-battery decision has its own page: https://v2lworkshop.co.uk/affordability/ev-vs-home-battery.

## Standards & sources

Standards (notably BS 7671) are cited by reference only and never reproduced. See the standards clause-index at https://v2lworkshop.co.uk/standards and the safety guidance at https://v2lworkshop.co.uk/safety. Notifiable electrical work must be designed, installed and tested by a competent person. Tariff and product figures are volatile — verify the current values from the supplier or manufacturer before relying on them.

- [Octopus Energy — Intelligent Octopus Go](https://octopus.energy/smart/intelligent-octopus-go/) — The cheap whole-home window structure (e.g. 23:30–05:30, whole-home; smart slots car-only). Rates are volatile — verify the current p/kWh.
- [Octopus Energy — REST API (products & unit rates)](https://docs.octopus.energy/rest/guides/endpoints/) — Public, unauthenticated tariff and half-hourly (Agile) unit rates — the source behind this page's optional “Connect Octopus for live rates” button. Octopus is the only supplier currently verified and integrated here; every other supplier stays manual or preset.
- [Ofgem — energy price cap](https://www.ofgem.gov.uk/energy-price-cap) — Regional unit rates and standing charges that bound a standard-rate baseline.
- [GOV.UK — Electric vehicle smart charge point regulations](https://www.gov.uk/guidance/regulations-electric-vehicle-smart-charge-points) — Default-off charging schedules and the randomised start delay that can disrupt a fixed-window plan.
- [myenergi — Zappi ECO/ECO+ charge rates](https://support.myenergi.com/hc/en-gb/articles/5780558509201-ECO-ECO-charge-rates-in-a-three-phase-zappi) — An example of a charger's minimum controllable charge current — confirm your own model against its manufacturer help page, never a forum.

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_Last reviewed: 2026-06-16. Written against: BS 7671:2018 + A4:2026. Education, not project-specific design advice; standards cited by reference only._