Solar Diverter vs Battery Storage: Which Is Right for Your Sussex Home?
Written by Green Earth Sussex — NAPIT Approved Electricians serving all of East & West Sussex.
You've got solar panels. You're generating electricity during the day that you're not fully using. What's the best way to capture that surplus energy rather than exporting it to the grid for a few pence per unit?
Two popular options are a solar diverter (also called an immersion diverter or solar iBoost) and a battery storage system. Both increase your self-consumption, but they work very differently and suit different households. Here's how to choose.
What Is a Solar Diverter?
A solar diverter (brands include myenergi Eddi, Solar iBoost, and Immersun) monitors your solar generation and household consumption in real time. When it detects surplus solar energy that would otherwise be exported, it diverts that power to your hot water immersion heater — effectively using free solar electricity to heat your water instead of gas or grid electricity.
Solar Diverter Pros
- Very low cost — typically £400–£700 installed
- Simple installation, no major electrical work
- Works with any existing solar system
- Reduces gas or electric water heating bills
- Very short payback period (2–4 years)
Solar Diverter Cons
- Only heats water — can't power other appliances
- No backup power capability
- Requires a hot water cylinder (not combi boilers)
- Limited savings compared to battery storage
- Can't use stored energy for evening electricity
What Is Battery Storage?
A battery storage system (such as Tesla Powerwall, GivEnergy, or Solax) stores surplus solar electricity in a lithium battery. You can then use that stored electricity at any time — in the evening, overnight, or during cloudy periods. Unlike a diverter, the stored energy can power any appliance in your home.
Battery Storage Pros
- Powers any appliance, not just hot water
- Backup power during grid outages
- Works with time-of-use tariffs for extra savings
- Much higher annual savings potential
- Ideal for EV charging from stored solar
Battery Storage Cons
- Much higher upfront cost (£3,500–£10,000+)
- Longer payback period (8–15 years standalone)
- Requires more complex installation
- Battery degradation over time (typically 10yr warranty)
Head-to-Head Comparison
| Factor | Solar Diverter | Battery Storage |
|---|---|---|
| Installed cost | £400–£700 | £3,500–£10,000+ |
| Annual savings | £100–£200 | £300–£600+ |
| Payback period | 2–4 years | 8–15 years (standalone) |
| Backup power | No | Yes (most systems) |
| Works with EV charging | No | Yes |
| Hot water cylinder needed | Yes | No |
| Time-of-use tariff benefit | No | Yes |
| Complexity | Low | Medium–High |
Which Should You Choose?
Choose a solar diverter if...
- You have a hot water cylinder (not a combi boiler)
- Budget is limited and you want the fastest payback
- You mainly want to reduce your gas or immersion heating bills
- You're happy with a simple, low-maintenance solution
Choose battery storage if...
- You want to power all your evening electricity from solar
- You have or plan to get an electric vehicle
- You want backup power during outages
- You're on or planning a time-of-use tariff
- You're installing solar and battery together (best economics)
Consider both if...
- You have a hot water cylinder AND want evening electricity from solar
- You want to maximise self-consumption across all energy uses
- Budget allows — a diverter + battery is the most comprehensive solution
Already Have Solar? We Can Add Either Option
Green Earth Sussex installs both solar diverters and battery storage systems as retrofits to existing solar PV installations across Sussex. Visit our Battery Retrofits page or our Battery Storage Systems page, or call us on 01273 076860 for a free assessment.
Need Help? Get a Free Quote Today
Our NAPIT approved electricians cover all of East and West Sussex. Call us or request a free no-obligation quote.
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