DNO Service Fuse: What It Is And Why It Matters
Your service fuse (cut-out fuse) limits the maximum current your home can draw from the grid. In Suffolk, UK Power Networks (UKPN) owns and maintains this fuse and the service head. Only the DNO may remove or change it. Typical single-phase ratings are 60A, 80A or 100A (roughly 13.8 kW, 18.4 kW or 23 kW at 230 V).
The DNO fuse sits before your electricity meter and consumer unit—think of it as the main gate. Electrification lifts demand: a 7.4 kW EV charger draws about 32 A; an air source heat pump commonly uses 1.5–3.5 kW while running with short peaks for defrost. Add an electric shower or induction hob and many 60A homes run out of headroom. See our guide to electrical upgrades for heat pumps to plan safely.
How To Know If You Need A Fuse Upgrade
Typical triggers: installing a heat pump, adding a 7.4 kW EV charger, running multiple electric showers, going all‑electric, or combining induction cooking with other large loads. If you have a 60A fuse, EV plus heat pump often justifies 80A or 100A.
- Check your current rating: it’s usually printed on the fuse carrier in the service head (e.g., 60A/80A/100A). If unclear, we’ll confirm from photos or with UKPN.
- Estimate coincident loads (what may run together). Examples: EV 32A; electric shower 40–50A; induction hob 10–20A after diversity; heat pump 8–16A typical running current.
- If likely peak use nears or exceeds your fuse rating, plan an upgrade or add smart load management.
- A professional assessment avoids nuisance trips, overheating, and non‑compliance.
Clima Tech provides a free desktop pre‑check and, if needed, manages the formal request. For timings around installs, see the heat pump installation journey.
Suffolk Specifics: UK Power Networks Process And Local Grid Context
For an increased load, UKPN reviews your address, existing service head and local network capacity. Straightforward like‑for‑like fuse swaps can be approved quickly. If cables are undersized, the position is non‑compliant, or relocation is needed, UKPN will survey and quote. Urban areas such as Ipswich and Bury St Edmunds are often quicker than rural/coastal locations where access and civils add time.
Common delays: poor access, out‑of‑spec meter position, undersized meter tails, missing main earthing/bonding, or a need for three‑phase. If you’re adding high loads or a workshop, read when Suffolk homes need three phase power to understand thresholds.
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Costs: What’s Free, What’s Chargeable, And What To Budget
Good news: a simple fuse upgrade (e.g., 60A to 80A/100A) is often free from the DNO. This covers the DNO fuse and service head only. Service cable upgrades, moving the position, or converting to three‑phase are chargeable and priced by UKPN after survey.
Allow for your side of the works too. Typical extras include new 25 mm² meter tails, a 100A isolator switch, SPDs and main earthing/bonding to current regs—usually hundreds of pounds, not thousands. Service cable or three‑phase works can run to several thousand depending on distance and civils. We’ll set expectations early and coordinate with our electrical installation services. Final costs depend on the site survey.
How Clima Tech Coordinates DNO Applications Alongside Your Install
We start with a maximum demand calculation and professional load assessment. We prepare clear photos of the service head, meter, isolator, consumer unit and earthing, collect your MPAN and permissions, then submit the increase‑in‑load request to UKPN on your behalf.
We liaise with your supplier for an isolator if needed, book the DNO visit, and sequence works to keep your heat pump or EV project on track. With 20+ years’ local experience and MCS, REFCOM, NICEIC and Gas Safe accreditations, we keep it safe, tidy and compliant. For joined‑up planning, see plan electrics EV solar heat pump Suffolk.
Lead Times And Sequencing: A Realistic Schedule For Suffolk Homes
Simple fuse swaps often complete within 2–6 weeks once approved. If the service cable needs upgrading or relocating, allow 6–12+ weeks for surveys, permissions and civils. Rural sites and long cable runs tend to take longer, and winter is typically busier.
We aim to complete the DNO upgrade before final commissioning. If the install must proceed earlier, we can fit temporary load management where appropriate and lift limits once the upgrade is done. Expect a planned power‑off window and clear access around the service head and meter; we’ll brief you in advance.
Smart Alternatives To Avoid Or Defer A Fuse Upgrade
Not every home needs an immediate upgrade. Options include:
- EV chargers with dynamic load balancing that cap charge current using a CT clamp on the meter tails.
- Priority switching to pause EV charging during a shower or heat pump defrost.
- Heat pump control to limit peak draw and use weather compensation to smooth demand.
- PV and batteries to shave grid peaks at busy times.
We fit protection and smart controls correctly—safety first, then optimisation. For options, see electrical protection for renewables, SPD, AFDD and load management.
This image was generated with AI and may not always represent the product or service exactly.
What We Need From You To Start The DNO Process
Clear photos speed approvals. Please send sharp images of:
- Service head and fuse rating (close‑up) and a wider shot of the whole setup.
- Meter and isolator (if fitted), consumer unit labels, and main earthing/bonding.
- The planned heat pump/EV charger location and cable route if known.
- Essential details: MPAN (from your electricity bill), full address, contact info, parking/access notes, and written permission if you’re not the owner.
- Tell us about future plans (induction hob, second EV, annex, sauna) so we can right‑size capacity now.
Real Suffolk Examples: Upgrades We’ve Delivered
Every property is different, but the process is consistent. Recent anonymised outcomes:
- Rural cottage: 60A to 100A for an air source heat pump and 7.4 kW EV charger. UKPN fuse swap approved; isolator and bonding upgraded. Lead time: 4 weeks. Seamless commissioning.
- Ipswich townhouse: 80A retained. We installed an isolator, new tails and SPD; no DNO cable work needed. Smart EV load balancing avoided an upgrade. Lead time: 2 weeks.
- Period home near Woodbridge: staged works to suit conservation needs. Fuse to 100A, meter move by supplier, then heat pump commission. Temporary load management kept the home running.
Compliance, Grants And Safety: Doing It Right First Time
Clima Tech designs and commissions to MCS for heat pumps and works to NICEIC standards and BS 7671 (18th Edition) for electrics. Our engineers hold REFCOM and Gas Safe where relevant. We ensure earthing and bonding are correct and specify protection such as SPDs and AFDDs where appropriate.
If you’re using the Boiler Upgrade Scheme, we align BUS paperwork with DNO timelines so funding and commissioning stay on track. The result is a safe, compliant install ready for a low‑carbon future.
Next Steps: Request Your Free Pre‑Check And Quote
Send us a few photos and basic details for a fast desktop pre‑check. We’ll confirm capacity, timelines and any likely costs, and recommend the best route—upgrade now, smart controls, or both.
When you’re ready, we’ll handle the DNO application, schedule works, and install your system with confidence. Start here: estimation form.
FAQs
Who decides my fuse rating?
UK Power Networks owns and sets your service fuse rating in Suffolk. We apply to them for any increase in load.
Is a fuse upgrade always needed for an EV charger?
Not always. Many homes with 80A or 100A are fine. For 60A, EV plus heat pump often needs an upgrade or smart load management.
How do I check my fuse size?
Look for the rating marked on the fuse carrier in the service head (e.g., 60A/80A/100A). If it’s unreadable, send us photos and we’ll advise.
How long will my power be off during the DNO visit?
For a simple fuse swap, typically under an hour. Cable or position works take longer; we’ll brief you in advance.
Will I be charged for a fuse upgrade?
Simple fuse swaps are often free. Cable upgrades, meter moves or three‑phase conversions are chargeable and quoted by UKPN.
Can smart controls replace a capacity upgrade?
They can manage peaks and may defer an upgrade. They’re not a substitute where the supply is clearly undersized.
Do I need three‑phase for a heat pump?
Most homes do not. Larger properties or multiple high loads may benefit. We’ll advise based on a full load assessment.
Can I pull the main fuse myself?
No. Only the DNO may remove or change the service fuse. It’s illegal and dangerous to do so yourself.