Is a Solar Diverter Worth It in 2026 UK?

• myenergi Eddi (premium): £549 + £200 install = £749 total
• Solar iBoost+ (budget): £329 + £180 install = £509 total
• Marlec Solar iBoost (mid): £349 + £180 install = £529 total
• Typical annual saving: £180–£320 (4kWp PV, daily immersion use)
• Payback period: 3–6 years on SEG <12p/kWh; 1–3 years on SEG <6p/kWh
• Lifespan: 10–15 years (Eddi has 3-year warranty)

Worth it if: SEG <12p/kWh, immersion-friendly cylinder, daily hot water demand. Skip if: SEG >15p/kWh or all-heat-pump heating.

Solar diverters only make sense when the opportunity cost of diverting beats the export tariff. Here is the simple rule:

Divert if: Gas equivalent cost (~7p/kWh) > SEG export rate. Export if: SEG export rate > gas equivalent cost (~7p/kWh).

For an all-electric home replacing immersion energy (~28p/kWh import), the break-even SEG is much higher (~22p/kWh) — diverting wins for almost any tariff. For a gas-heated home, the immersion only runs when you need it; you are replacing ~7p/kWh gas, so diverting only wins below ~7p/kWh SEG. Most fixed SEG tariffs in 2026 sit at 4.1p (Octopus Outgoing Fix), 5.5p (E.ON Next Export Exclusive), or 12p (British Gas Export & Earn) — meaning most homes win.

1. High SEG export tariff (>15p/kWh). Octopus Outgoing Agile occasionally pays 25p+/kWh during the summer middle-of-day. If you are on this, export rather than divert.

2. Heat-pump primary heating. A heat pump produces hot water at ~1/3 the energy cost of a resistance immersion. The diverter saving shrinks dramatically.

3. Battery storage already installed. Storing surplus in a battery and self-consuming it later at ~28p/kWh import beats diverting to immersion at ~7p/kWh gas-equivalent — every time.