Tesla vs Enphase Battery Comparison Calculator

Enter your backup goal and priority — get a side-by-side table: units needed, cost, efficiency, TOU savings, and a recommendation for your situation.

Your electricity profile

Monthly electricity bill?

State?

Utility rate?

$/kWh

Existing solar system?

TOU pricing (optional)

TOU pricing plan?

Disabled

Backup & priority

Desired backup hours (essential loads)?

Your top priority?

Side-by-side comparison

Recommendation

IQ Battery wins on lowest total net cost

Metric	Tesla Powerwall 3	Enphase IQ 5P Recommended
Capacity per unit	13.5 kWh	5 kWh
Units needed (8h backup)	1 unit	3 modules
Total capacity	13.5 kWh	15 kWh
Total installed cost	$18,000	$16,500
Net cost after 30% ITC	$12,600	$11,550
$/kWh stored (net)	$933/kWh	$770/kWh
Continuous power output	7.6 kW	11.52 kW
Peak power	22 kW	23.04 kW
Round-trip efficiency	90%	96%
Warranty	10 years	10 years
Expansion cost/kWh (after ITC)	$933/kWh	$770/kWh
10-yr total cost (net - savings)	$5,400	$2,550

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How to Use This Calculator

Enter your electricity profile and backup goal

Start with your monthly electricity bill, state, and how many hours of backup you want from essential loads (~1.5 kW: lights, fridge, router, phone charging). The calculator determines how many units each brand needs to hit your backup target — Powerwall 3 at 13.5 kWh/unit vs. IQ Battery 5P at 5 kWh/module — then computes cost, power, and savings side by side.

Set your top priority

The priority dropdown controls the recommendation badge. "Lowest cost" compares net $/kWh. "Best reliability" favors Enphase's distributed architecture, which has no single inverter to fail. "Most expandable" favors Enphase's modular add-anytime design. "Maximum storage" favors Tesla, which offers 54 kWh (4 units) at a lower $/kWh than Enphase's 40 kWh max.

Enable TOU pricing if applicable

If your utility offers Time-of-Use pricing, enabling it shows TOU arbitrage savings for each brand. Enphase's 96% round-trip efficiency means slightly more daily kWh recovered from arbitrage than Powerwall's 90% — a meaningful difference when cycling daily for 10 years.

The Formula

kWh Needed = Desired Backup Hours × 1.5 kW essential load Powerwall Units = ⌈kWh Needed ÷ 13.5 kWh⌉ (max 4) Enphase Modules = ⌈kWh Needed ÷ 5 kWh⌉ (max 8) Total Cost = Units × Cost per Unit Net Cost = Total Cost × (1 − 0.30 ITC) $/kWh Stored = Net Cost ÷ Total kWh TOU Arbitrage = Total kWh × RTE × (Peak − Off-Peak) × 365 10-yr Total Cost = Net Cost − Annual Savings × 10

The key differentiators: Powerwall's 7.6 kW continuous power handles more simultaneous loads per unit, while Enphase's 96% RTE returns more energy from each storage cycle. For the same backup duration, you'll typically need more Enphase modules (smaller each) vs. fewer Tesla units (larger each) — which affects both total cost and installation complexity.

Example

David — 12 hours backup, reliability priority in Florida

David lives in Florida where hurricane season means 12+ hour outages. He has an 8 kW solar system and wants the most reliable backup. He pays $0.13/kWh.

Monthly bill$180/mo ($0.13/kWh)

Existing solar8 kW

Desired backup12 hours essential loads

PriorityBest reliability

Side-by-side result

Tesla: units needed2 Powerwalls (27 kWh)

Tesla: net cost$25,200

Enphase: modules needed4 IQ 5P modules (20 kWh)

Enphase: net cost$15,400

Round-trip efficiency90% (Tesla) vs 96% (Enphase)

RecommendationEnphase — distributed reliability + lower cost

For David's reliability-first goal, Enphase wins on two counts: lower net cost ($15,400 vs $25,200) and distributed module architecture that has no single inverter failure point. With Florida sun recharging the system daily, 4 modules provide effective indefinite essential backup through storm season.

FAQ

Is Tesla Powerwall or Enphase IQ Battery better? ▼

Neither is universally better — it depends on your situation. Tesla Powerwall 3 wins when you want: maximum storage in one unit (13.5 kWh vs 5 kWh), highest continuous power (7.6 kW vs 3.84 kW per unit), or integrated solar inverter (Powerwall 3 has a built-in inverter). Enphase IQ Battery 5P wins when you want: highest round-trip efficiency (96% vs 90%), modular expandability, existing Enphase microinverter integration, or best reliability (no single inverter failure point). For most homeowners with existing Enphase solar, IQ Battery is the clear choice. For new installations seeking maximum capacity at lowest $/kWh, Powerwall often wins.

Which battery has better round-trip efficiency? ▼

Enphase IQ Battery 5P wins with 96% round-trip efficiency vs Tesla Powerwall's 90%. This means for every 100 kWh stored, IQ Battery returns 96 kWh vs Powerwall's 90 kWh. Over 10 years of daily cycling, this 6% difference adds up to thousands of additional kWh from IQ Battery — directly reducing how much grid electricity you need to buy. For TOU arbitrage (daily cycling), this efficiency advantage is especially valuable.

Can I use Tesla Powerwall with non-Tesla solar panels? ▼

Yes. Powerwall 3 can be AC-coupled with any solar inverter or DC-coupled with its built-in inverter for new installations. If you have an existing non-Tesla solar system (SolarEdge, Enphase, or string inverter), Powerwall connects on the AC side — no re-wiring of panels required. Powerwall 3's built-in inverter is only used for new solar DC connections. AC coupling is slightly less efficient (adds one more conversion step) but widely compatible.

Which battery is easier to expand later? ▼

Enphase wins on expandability. IQ Battery modules can be added one at a time at any point — there's no architectural constraint. You could start with 2 modules (10 kWh) and add 2 more in 3 years without any system redesign. Tesla Powerwall expansion is possible (up to 4 units) but requires a separate Tesla installation appointment. Both carry the same 30% ITC on new units added — so expanding later still qualifies for the federal tax credit.

What happens during a power outage with each system? ▼

Both systems automatically island from the grid and power your home during an outage. Powerwall 3 transitions in under 20 milliseconds — fast enough that most electronics don't notice. It provides 7.6 kW continuous, enough to run AC, EV charger, and major appliances simultaneously from one unit. Enphase IQ Battery also provides seamless transition (typically under 2 seconds) and 3.84 kW per module continuous — more modules can be stacked for higher loads. Both work with paired solar to recharge during the day. Powerwall has a Storm Watch feature that auto-charges to full before predicted outages.

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