SunStore

Solar + Battery Self-Consumption ROI Calculator

Self-used solar is worth your retail rate; exported solar isn't — see the yearly value and what a battery adds.

Annual solar generation (kWh)

Self-consumption with battery (%)

Self-consumption without battery (%)

Retail electricity rate ($/kWh)

Export / feed-in rate ($/kWh)

Annual value with battery

$1,155

Self-consumed solar is worth your full retail rate; exported solar is only worth the (usually much lower) feed-in rate. That gap is exactly why a battery — which raises self-consumption — adds value. Weigh the yearly uplift against the battery's cost and lifespan.

Value without battery: $642
Extra value from battery / year: $513
Solar self-consumed: 4,500 kWh

What you entered

Annual solar generation (kWh): 6000Self-consumption with battery (%): 75Self-consumption without battery (%): 30Retail electricity rate ($/kWh): 0.24Export / feed-in rate ($/kWh): 0.05

1
Self-consumed energy (valued at retail)
6000 × 75%= 4500 kWh
2
Exported energy (valued at feed-in)
6000 − 4500= 1500 kWh
3
Annual value with battery
4500 × $0.24 + 1500 × $0.05= $1,155
4
Annual value without battery (30% self-use)
self × retail + export × feed-in= $642
5
Extra value the battery adds
$1,155 − $642= $513

Result

Annual value with battery: $1,155

Your solar is worth about $1,155/year with a battery vs $642 without — the battery adds roughly $513 a year by shifting exports (paid $0/kWh) into self-use (worth $0/kWh).

Annual value of solar with and without a battery, by system output

Every row values a year of solar generation twice: once at the 30% self-consumption a typical battery-free home achieves, and once at the 75% a battery-backed home reaches by storing midday surplus for the evening. Self-consumed energy is valued at a $0.24/kWh retail rate because it replaces a purchase, and exported energy at a $0.05/kWh feed-in rate. The final column is the difference, which is the battery's yearly value uplift.

Annual generation (kWh)	Self-consumed with battery (kWh)	Value without battery	Value with battery	Battery uplift per year
2,000	1,500	$214	$385	$171
3,000	2,250	$321	$578	$257
4,000	3,000	$428	$770	$342
5,000	3,750	$535	$963	$428
6,000	4,500	$642	$1,155	$513
7,000	5,250	$749	$1,348	$599
8,000	6,000	$856	$1,540	$684
10,000	7,500	$1,070	$1,925	$855
12,000	9,000	$1,284	$2,310	$1,026

The uplift is driven almost entirely by the gap between the retail and export rates, not by the size of the battery. Holding the 6,000 kWh row fixed and changing only the export rate: at $0.00 export the battery adds $648 a year, at $0.05 it adds $513, at $0.12 only $324, and at $0.20 just $108. Where a feed-in tariff pays close to the retail rate, a battery earns very little. The 30% and 75% self-consumption figures are typical averages - your real split depends on when your household actually uses power, so half-hourly interval data gives a far better answer than an annual average. These are gross annual values only: they exclude the cost of the panels and battery, financing, degradation, inverter replacement, and any tax credits or grants. Illustrative - run your own numbers with your local export rules and installed quotes before buying.

A solar-plus-battery ROI calculator estimates the annual financial value of a rooftop solar system and, crucially, how much extra a home battery adds on top. The single most important idea in home solar economics is that not all solar kilowatt-hours are worth the same. Energy you use in your own home the moment it is generated — self-consumption — is worth your full retail electricity rate, because it directly replaces power you would otherwise have bought. Energy you export to the grid is worth only the feed-in or export rate, which in most markets today is a fraction of the retail rate. This gap is the entire reason batteries make financial sense, and this tool quantifies it.

The calculation values your annual solar generation in two buckets. It multiplies the share you self-consume by the retail rate, because that is the purchase you avoid, and it multiplies the exported remainder by the export rate, because that is what the grid pays you. Added together, that is the annual value of your solar at a given self-consumption level. A typical solar-only home self-consumes only about 30% of what it generates, because production peaks midday when the house is often empty, so most of the value leaks out as cheaply-paid exports. A battery stores that midday surplus and releases it in the evening, pushing self-consumption up to 70-80%. The calculator computes the annual value at both self-consumption levels — with and without a battery — and reports the difference as the battery's yearly value uplift.

That uplift is the honest number to judge a battery against, and the source research is right to frame it around local export rules and real interval data. Where the export rate is close to the retail rate (generous feed-in), a battery adds little, because exporting is already well paid; where the export rate is low or zero, the same battery adds a great deal, because every kilowatt-hour shifted from export to self-use captures the full retail-minus-export spread. Real self-consumption also depends on the shape of your generation and usage through the day, which is why serious analysis uses interval data rather than annual averages. Use this calculator to size the annual value and the battery uplift at your own rates, then compare the uplift against the battery's installed cost and warranted lifespan to judge payback. It estimates annual value only and does not include system cost, degradation, financing, or tax credits — layer those on before making a purchase decision.

Why self-consumption is the whole game

Self-consumed solar avoids buying power at the retail rate; exported solar earns only the feed-in rate. With retail at $0.24 and export at $0.05, every kilowatt-hour you shift from export to self-use is worth an extra $0.19. A solar-only home self-consumes ~30%; a battery pushes that to 70-80%, and that shift — not the battery's raw capacity — is where the money is.

The export rate decides the battery's worth

A battery's value uplift depends entirely on the gap between your retail and export rates. Under a generous feed-in tariff where export nearly equals retail, a battery barely helps. Under a low or zero export rate, the same battery captures the full spread on everything it shifts, and its annual value can be several times higher. Always run it with your actual local export rules.

Frequently asked questions

My system makes 6,000 kWh/year — what's it worth with and without a battery?

At 30% self-consumption (solar only), 1,800 kWh at $0.24 plus 4,200 kWh exported at $0.05 is about $642/year. A battery raising self-consumption to 75% makes it 4,500 kWh at $0.24 plus 1,500 kWh at $0.05 ≈ $1,155/year. So the battery adds roughly $513 a year at these rates.

Why isn't exported solar worth as much as the solar I use?

Because you're paid the export (feed-in) rate for it, which in most markets is well below the retail rate you pay to buy power. Using your own solar avoids a retail-rate purchase; exporting only earns the lower wholesale-ish rate. The bigger that gap, the more valuable it is to self-consume rather than export.

Does a bigger battery always add more value?

Only up to the point where it captures your daily surplus. Once a battery is large enough to store all the midday solar you can use by evening, adding more capacity does nothing for self-consumption and just adds cost. Size the battery to your daily surplus and evening load, not to the largest unit available.

How is this different from the home battery tariff optimizer?

The tariff optimizer values charging cheap off-peak grid power and discharging at peak (arbitrage), independent of solar. This calculator values solar self-consumption vs export and the battery's role in raising it. Many homes benefit from both — model each and add them for the battery's total annual value.