Summary
Solar PV diverters have become a standard add-on quote for anyone doing solar work in the UK, driven by falling Smart Export Guarantee (SEG) rates making self-consumption more valuable than exporting. The job is straightforward for anyone competent in domestic electrical work — a CT clamp on the incoming supply tails, a control unit near the consumer unit, and a cable run to the immersion heater — but pricing it well means understanding what varies the labour time and what customers are actually comparing your quote against.
The two most common quoting scenarios are different jobs commercially even though the hardware is the same: fitting a diverter as part of a new PV installation (the electrician is already on site, cable routes are being planned from scratch, so it's genuinely an add-on) versus retrofitting a diverter to an existing PV system with no diverter (a standalone visit, existing consumer unit and immersion circuit to work around, and often an existing cylinder that needs checking for compatibility).
The most common pricing mistake is treating every diverter job as the same fixed price. Retrofit jobs on unfamiliar cylinders, older wiring, or three-phase supplies take meaningfully longer and carry more risk of an unexpected second visit — price the survey and the unknowns, not just the "standard" install.
Key Facts
- How it works — a CT (current transformer) clamp on the meter tails measures import/export in real time; when generation exceeds household demand, the diverter unit diverts the surplus (via phase-angle/burst-fire control) to the immersion heater element instead of exporting it to the grid.
- No DNO notification required for the diverter itself — G98/G99 notification requirements apply to the PV generation system, not to a diverter added afterwards; installing a diverter alone does not trigger a new DNO application.
- Part P applies — connecting a diverter into the consumer unit and to the immersion circuit is notifiable electrical work in a kitchen/bathroom-adjacent circuit context, or simply good practice to self-certify via a competent person scheme (NICEIC, NAPIT) even where not strictly notifiable.
- MCS is not typically required for the diverter alone — MCS certification is a PV/generation-system requirement for Smart Export Guarantee eligibility, not a requirement of the diverter hardware itself, but if diverter work forms part of a wider PV/battery installation being MCS-certified, it should be documented as part of that system.
- Single-phase vs three-phase — most domestic UK installs are single-phase; three-phase properties need a diverter rated for three-phase monitoring (or three single-phase units, one per phase), adding cost and labour.
- Twin-element cylinders — diverters are usually wired to the lower immersion element (larger volume heated first); check the cylinder has a lower element and thermostat, or note the cost of adding one.
- Existing immersion circuit condition — always check the immersion heater cable, isolator and thermostat before quoting a fixed price; a like-for-like connection is quick, but a corroded/undersized circuit needing rewiring adds material and time.
- CT clamp placement — must go on the correct tails to measure grid import/export accurately, not generation output directly; incorrect placement means the diverter reacts to the wrong signal.
- App/Wi-Fi setup — most diverters offer app monitoring and boost scheduling; budget 15–30 minutes for network setup and customer handover, separate from the electrical work.
- Compatibility with battery storage — where a home battery is already fitted, the diverter's priority order (battery charge vs immersion diversion) needs to be configured correctly, or the two systems can compete for the same surplus power.
- Legionella/thermostat safety — a diverter must not be relied on as the sole means of reaching pasteurisation temperature; the cylinder thermostat and periodic full-temperature heating cycle must remain functional regardless of solar input.
- Retrofit vs new-build pricing gap — quoting a diverter alongside a new PV install is cheaper per job because scaffold, isolation and cable routes are already being handled; a standalone retrofit visit carries its own callout and survey overhead.
Quick Reference Table
Spending too long on quotes? squote turns a 2-minute voice recording into a professional quote.
Try squote free →| Scenario | Typical labour time | Materials (trade cost) | Supply & fit price (ex VAT) |
|---|---|---|---|
| Diverter added during new PV installation | 1–2 hr | £200–£320 | £150–£300 (as add-on to PV job) |
| Standalone retrofit to existing single-phase PV system | 2–4 hr | £220–£380 | £350–£650 |
| Retrofit with immersion circuit upgrade needed | 3–5 hr | £280–£450 | £550–£850 |
| Three-phase property (single diverter unit, three-phase rated) | 3–5 hr | £350–£550 | £650–£950 |
| Add-on: app/Wi-Fi setup and customer handover | 0.25–0.5 hr | — | £30–£60 |
| Add-on: priority configuration alongside existing battery storage | 0.5–1 hr | — | £60–£120 |
Detailed Guidance
Surveying before quoting a fixed price
Always inspect the existing immersion heater circuit, cylinder type (single vs twin element), and consumer unit space before committing to a fixed price on a retrofit job. A cylinder without a lower immersion element, an undersized or degraded immersion cable, or a consumer unit with no spare ways all add cost that a phone-quote will miss. Offer a "confirmed on survey" price for anything other than a straightforward like-for-like retrofit.
Pricing the PV-installation add-on correctly
When quoting a diverter as part of a new PV system, don't just add the hardware margin — factor in the marginal labour time properly. It's genuinely faster to fit a diverter while the consumer unit is already open and cable routes are being run for the PV isolator and generation meter, but it still adds real time for the CT clamp fitting, immersion cable run and commissioning. Treat it as a distinct line item on the quote so the customer can see the incremental cost, not a "free extra."
Materials margin and unit selection
Diverter units vary by monitoring accuracy, app functionality and phase configuration rather than a wide quality spread — a 25–35% margin on the unit itself is standard. Standardise on a single-phase and a three-phase-capable option to keep quoting simple, and always separate the unit cost from the immersion circuit materials (cable, isolator, thermostat if needed) in the quote so cylinder-related upgrades are clearly itemised rather than buried in the diverter price.
Configuring alongside existing battery storage
Where a customer already has battery storage, clarify with them (and configure in the diverter/inverter settings) whether battery charging or immersion diversion should take priority for surplus generation. This is a configuration task, not a hardware one, but it needs to be quoted and delivered correctly — a mis-set priority order means the customer's expensive battery loses out to their kettle-water heater, which is rarely what they want in winter when solar surplus is scarce.
Common quoting mistakes
The most frequent error is quoting a diverter at a flat rate regardless of scenario, then losing margin on the retrofit jobs that turn out to need cylinder or circuit work. The second most frequent error is failing to separate DNO/G98/G99 considerations from the diverter itself — customers and even some tradespeople conflate "installing solar electronics" with "needs DNO notification," when the diverter itself does not trigger this; only the underlying PV generation system does.
Frequently Asked Questions
Does adding a solar diverter require DNO notification?
No — the diverter itself does not export or generate electricity to the grid, so it does not trigger a G98 or G99 notification. DNO notification requirements apply to the PV generation system (or battery storage system) being connected to the grid, which is a separate consideration from adding a diverter to redirect self-generated surplus to an immersion heater.
Is MCS certification needed to fit a diverter?
Not for the diverter in isolation. MCS certification is required for the PV (and battery) generation system to qualify for Smart Export Guarantee payments and government incentive schemes — it isn't a requirement specific to the diverter hardware. If the diverter is being fitted as part of a wider MCS-certified PV installation, document it as part of that system's specification for consistency, but a standalone diverter retrofit to an already-installed system doesn't need separate MCS sign-off.
Do I need to be Part P registered to fit a diverter?
Yes, in effect — the work involves connecting into the consumer unit and wiring into (or alongside) the immersion heater circuit, which is domestic electrical installation work. Even where the specific connection point isn't on the strict Part P notifiable list, self-certifying the work through a competent person scheme (NICEIC, NAPIT) and issuing a minor works or electrical installation certificate is the correct professional standard.
Why does a retrofit diverter cost more than one fitted with a new PV system?
Because a retrofit is a standalone site visit with its own survey, isolation and access overhead, working around an existing consumer unit and immersion circuit that may need upgrading. A diverter fitted during a new PV installation shares scaffold, isolation and cable-routing time with the main job, so only the diverter-specific labour and hardware need to be costed separately.
Regulations & Standards
BS 7671:2018+A4:2026 — UK wiring regulations governing the immersion circuit and consumer unit connection work.
Engineering Recommendation G98 — DNO notification for PV/generation systems up to 16A per phase; applies to the PV system, not the diverter.
Engineering Recommendation G99 — DNO notification/approval for larger PV/generation systems; applies to the PV system, not the diverter.
MCS (Microgeneration Certification Scheme) — certification scheme for PV and battery installations, gateway to Smart Export Guarantee eligibility.
Part P, Building Regulations (England & Wales) — competent person self-certification for domestic electrical installation work.
Smart Export Guarantee (SEG) — government-mandated payment scheme for exported renewable electricity, the financial driver behind diverter demand.
Notifying DNOs | MCS — official MCS guidance on G98/G99 notification scope
DNO Application Checker | G98 vs G99 | Payaca — practical G98/G99 comparison
The DNO Guide, G98, G99 and G100 applications for UK solar — DNO notification process detail
myenergi eddi solar power diverter installation with WiFi | Brian Dorey — practical diverter installation process reference
solar diverter explained — how a solar diverter works technically
solar pv installation pricing guide — pricing the wider PV installation this often accompanies
solar pv — PV system fundamentals, DNO notification and MCS certification
mcs certification explained — MCS certification process and SEG eligibility