If your site has an HV supply above 500 kVA but runs comfortably within an LV supply, switching to LV could cut your electricity costs by £13,000 to £37,000 a year. Forecast transmission increases in April 2027 would push that to £26,000 to £50,000.
It is aimed at three kinds of site, both on an HV connection of 500–1,100 kVA but now peaking at a few hundred kVA:
- Buildings that used to house intensive manufacturing but no longer do. Former mills, foundries, print works and engineering shops now used for storage, distribution, light assembly, offices or multi-let units. The heavy plant has gone, but the HV supply and its charges are still there.
- Businesses that have cut their demand through efficiency. Years of LED lighting, variable-speed drives, more efficient compressors and chillers, heat recovery or on-site solar can take a site’s peak well below what its HV connection was sized for. The saving on energy is real, but the fixed charges haven’t followed it down.
- Mid-sized businesses that never needed all of it. Manufacturers, warehouses, cold stores and food producers whose connection was sized for growth or plant that never arrived.
All of these sites are charged as HV Band 2 customers, whatever they use today. The same site on a large LV supply would be in LV Band 4, which costs far less in fixed charges.
Why HV Band 2 costs more
An HV Band 2 site pays about £62,500 a year in fixed charges before it uses a single unit; on LV Band 4 the same charges are about £21,600. Since April 2022 most network costs have been charged per site according to its band. The band depends on connection voltage and agreed capacity, not on how much you use.
| HV Band 2 | LV Band 4 | Difference | |
| Agreed capacity | over 500 up to 1,100 kVA | over 250 kVA | |
| Standing charge (UK average) | £5,207/month | £1,798/month | £40,910 a year less on LV |
| of which transmission (TNUoS) residual | £117.15/day | £38.18/day | £28,820 a year less on LV |
| Capacity charge (UK average) | £0.090/kVA/day | £0.084/kVA/day | slightly less on LV |
The catch is the higher LV unit rate, caused by higher distribution unit charges and line losses. For most sites using under about 2 million kWh a year, the fixed-charge saving is far larger.
Standing charges, capacity charges and unit rates are the simple average of EDF’s half-hourly deemed rates across all 14 UK distribution regions, from 1 September 2026. They are used because they price HV and LV on the same basis; your own contract rates will differ. TNUoS figures are NESO’s final 2026/27 tariffs, which are the same in every region.
Worked example: a 600 kVA site peaking at 300 kVA
A site with a 600 kVA HV supply, a 300 kVA peak and 500,000 kWh a year of use would save about £36,600 a year by moving to a 400 kVA LV supply. That rises to about £49,800 from April 2027.
Illustrative site: 600 kVA HV supply, 300 kVA peak, 500,000 kWh a year (84% day / 16% night), moving to a 400 kVA LV supply. EDF half-hourly deemed rates, average of 14 UK regions, from 1 September 2026; NESO 2026/27 final and October 2026 forecast 2027/28 TNUoS. Excludes conversion cost and HV maintenance savings.
Most of the saving is the drop in fixed charges, and the transmission charge alone is worth about £28,800 a year. Giving up 200 kVA of unused capacity adds £7,400. The higher LV unit rate takes back £11,700, still well short of the gain.
How consumption changes the saving
The more a site uses, the smaller the saving, but a 600 kVA site still comes out ahead until it uses about 2.1 million kWh a year, or 2.6 million from April 2027.
Same 600 kVA → 400 kVA site at different consumption levels. EDF half-hourly deemed rates, average of 14 UK regions, from 1 September 2026; NESO TNUoS 2026/27 final and 2027/28 forecast. Assumes 84% day / 16% night use.
Each line starts at the yearly fixed-charge and capacity saving and falls by about 2.35p for every kWh used. At 1 million kWh a year the saving is about £24,900 now and £38,100 from April 2027; at 1.5 million it is about £13,100 and £26,300. Sites with a larger HV supply save slightly more, because they give up more capacity.
April 2027 makes the gap wider
NESO forecasts the HV Band 2 transmission charge rising 43% in April 2027. That would add about £13,200 a year to the saving from moving to LV Band 4.
| TNUoS residual (£/site/day) | 2026/27 (final) | 2027/28 (forecast) | Change |
| HV Band 2 | £117.15 | £167.71 | +43% |
| LV Band 4 | £38.18 | £52.49 | +37% |
| Gap per year | £28,820 | £42,060 | +£13,230 |
The 2027/28 figures are NESO’s October 2026 five-year view. NESO’s draft 2027/28 tariffs are due in November 2026 and final tariffs normally follow at the end of January, so these may still change. NESO expects residual charges to keep rising until 2031.
What it costs and what to check
With savings of £30,000 or more a year, a typical conversion pays back in two to three years: a £75,000 quote against a £36,600 annual saving pays back in just over two years. Your network operator (DNO) quotes the actual cost, which depends on:
- Who owns the transformer. Most HV customers own their transformer and switchgear. The DNO may adopt them, replace them, or supply you from a new substation.
- Distance and groundworks. A substation on or next to the site is far cheaper to connect than one down the road.
- The LV capacity you need. LV supplies above roughly 1,000 kVA are rarely practical.
You also stop paying to maintain, test and operate HV equipment, and an ageing transformer stops being your liability.
Before committing, check:
- Your real peak demand over 12 months. The LV supply needs to cover it with sensible headroom.
- Your current band. Your bill or DNO will confirm it. A site at exactly 500 kVA is in HV Band 1, not Band 2, and moving to LV Band 4 would cost it more.
- Which band the new supply will be in. Bands are normally fixed until 2031, so get the DNO to confirm the LV band in writing before you sign.
- Your plans. If you expect to add heavy plant, make sure the LV supply has room for it.
Find out what your site could save
Avails Energy will review your HV supply free of charge. Send us a recent bill and your half-hourly data, and we will:
- Confirm your current band and compare your agreed capacity with your real peak demand
- Estimate your saving on LV, using your own contract rates
- Arrange a site visit and quote for the works
- Show you the payback before you commit to anything
Contact Rory Ingham at rory@avails.co.uk or on 0113 873 1505, or visit avails.co.uk.
