TL;DR:
- Powerwall 3 offers 13.5 kWh of usable storage with an integrated inverter — best for whole-home backup
- Enphase IQ Battery 5P is modular, expands in 5 kWh increments, and integrates seamlessly with Enphase solar systems
- For most homes, Powerwall wins on backup power; Enphase wins on flexibility and installer availability
The home battery storage market has largely consolidated around two dominant choices for residential buyers: the Tesla Powerwall and the Enphase IQ Battery. Both pair with solar, both cover the core use case of storing daytime solar energy for evening use, and both are available in the UK and US. The differences come down to system architecture, backup capability, and how deeply you’re already invested in each ecosystem.
Specs Side by Side
| Feature | Tesla Powerwall 3 | Enphase IQ Battery 5P |
|---|---|---|
| Usable capacity | 13.5 kWh | 5 kWh per unit (stackable) |
| Round-trip efficiency | 97.5% | 96% |
| Continuous power output | 11.5 kW | 3.84 kW per unit |
| Peak power output | 22 kW (10 sec) | 7.68 kW per unit |
| Integrated inverter | Yes (solar + battery) | No (AC-coupled) |
| Backup time (average home) | 12–24 hours | 4–8 hours (1 unit) |
| Warranty | 10 years / 70% capacity | 15 years / 70% capacity |
| Approximate installed cost (UK) | £10,500–£12,000 | £7,000–£9,500 (1 unit) |
Backup Capability: Where Powerwall Has a Clear Edge
Whole-home backup power is where the Powerwall pulls ahead decisively. The Powerwall 3’s 11.5 kW continuous output can run an air conditioning unit, fridge, EV charger, and most of the rest of a home simultaneously. Its 22 kW peak handles motor startups — the moment an HVAC compressor kicks on and draws 3–5 times its running load.
A single Enphase IQ Battery 5P outputs just 3.84 kW continuously — enough for lights, sockets, fridge, and a laptop, but not a heat pump or electric shower. To match Powerwall’s backup capability, you’d need to stack three IQ Battery 5P units, pushing the cost well above Powerwall territory.
If uninterrupted whole-home backup during extended power cuts is your priority, Powerwall is the right choice.
Modular Flexibility: Where Enphase Wins
The Enphase IQ Battery 5P shines when you want to start small and scale. A single 5 kWh unit handles the evening solar self-consumption use case — shifting afternoon solar production to cover the 6–10pm peak rate window — at a lower entry cost. Add a second unit when your usage grows or when you want more backup coverage. Each unit is independently certified, so you’re not locked into replacing the whole system.
Enphase also has a broad installer network. The AC-coupled design means an IQ Battery can be added to an existing solar system regardless of inverter brand — no system redesign required. If you already have solar from a different manufacturer, this flexibility matters.
Software and Monitoring
Both platforms offer strong monitoring apps, but they differ in approach.
Tesla App is clean and intuitive, showing real-time energy flows between solar, battery, grid, and home. The Storm Watch feature automatically charges the Powerwall to 100% when severe weather is forecast — useful for the UK’s occasional winter storms. Powerwall also supports time-based charging, so it can top up from cheap overnight grid electricity on tariffs like Octopus Go.
Enphase App (Enlighten) offers panel-level monitoring when paired with Enphase microinverters, giving you production data for every individual panel. For troubleshooting underperformance, this granularity is genuinely useful. If you’re already on an Enphase solar system, staying in the ecosystem makes complete sense.
Installation Requirements
Powerwall 3 includes an integrated inverter, which simplifies new solar installations — one device handles both solar conversion and battery management. For retrofitting onto an existing non-Tesla solar system, a Tesla Gateway is required, adding cost and complexity.
Enphase IQ Battery is AC-coupled, meaning it connects to your electrical panel and works with any existing solar inverter. This makes it straightforward to retrofit without touching your existing solar setup.
UK Pricing and VAT
In the UK, battery storage attracts 0% VAT (as part of a solar system). That applies whether you’re installing with new solar or adding storage to an existing system.
A single Powerwall 3 installed typically costs £10,500–£12,000 in the UK. After 0% VAT, no additional reduction — but you’re not paying the 20% VAT you’d normally expect on electrical goods.
A single Enphase IQ Battery 5P installed runs £7,000–£9,500. To match Powerwall capacity at ~15 kWh, you’d be looking at £18,000–£24,000 for three units.
Which Should You Choose?
Choose Powerwall 3 if:
- You want whole-home backup with one device
- You’re doing a new solar installation (the integrated inverter simplifies the setup)
- You’re comfortable in the Tesla ecosystem and want Octopus VPP compatibility
Choose Enphase IQ Battery if:
- You have an existing Enphase solar system
- You want to start with one unit and expand later
- Your priority is daily solar self-consumption rather than extended backup
- You want panel-level monitoring alongside battery management
For most homeowners doing a new solar-plus-battery install, Powerwall 3 delivers the best backup performance per pound. For existing Enphase solar owners or those wanting modular expansion, the IQ Battery 5P is the natural fit. Either way, the 0% VAT on battery storage makes 2026 a reasonable time to add storage to a solar system.