Size the home battery you actually need in kWh, estimate the installed cost, and apply the 30% federal credit — plus when storage is genuinely worth it.
SCReviewed by Sarah Chen, Energy AnalystUpdated May 28, 2026Sources: DSIRE, NREL, IRS
Battery storage of 3 kWh or larger qualifies for the 30% federal credit — most valuable where outages or time-of-use rates are common. Photo: American Public Power Association / Unsplash
Quick answerMost homeowners need a 10–13 kWh battery to back up essentials for a day. At ~$1,000/kWh installed, that's about $11,000, or $7,700 after the 30% federal credit (storage 3 kWh+ qualifies). Whole-home backup with central AC needs 25–40 kWh.
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Size your battery
10 kWh
Fridge + lights + Wi-Fi + phones ≈ 5–8 kWh/day. Add AC/well pump for more.
1 day(s)
%
Lithium (LFP) batteries safely use ~90–100%.
$
2026 installed cost: ~$1,000/kWh before the 30% credit.
Recommended battery size
11
kWh usable capacity
Est. cost
$11,000
After 30% credit
$7,700
Typical product
1 unit
Batteries 3 kWh and larger qualify for the 30% federal credit. Backup value is highest where outages are common or time-of-use rates are steep.
How this calculator works
1
Set your daily backup energy
How much energy you want to keep running each day, in kWh.
2
Choose days of autonomy
How many days you want to run without grid or sun.
3
Account for depth of discharge
Lithium batteries safely use ~90% of capacity.
4
Get size and cost
We compute usable kWh, installed cost and your net after the 30% credit.
How big a solar battery do you need?
Battery sizing starts with one question: what do you want to keep running, and for how long? Whole-home backup needs far more capacity than running just the essentials. Here's a rough guide to daily energy by goal:
Backup goal
Daily energy
Battery (1 day)
Essentials (fridge, lights, Wi-Fi, phones)
5–8 kWh
~8 kWh
Essentials + a few outlets & TV
8–12 kWh
~13 kWh
Add window AC or well pump
12–20 kWh
~20 kWh
Whole-home (incl. central AC)
25–40 kWh
27–40 kWh
Is a solar battery worth it?
A battery makes the most financial sense if you have frequent grid outages, live under steep time-of-use rates (charge cheap at night or from solar, discharge during expensive peak hours), or your utility has poor net metering so storing your own power beats exporting it. The 30% federal credit applies to storage of 3 kWh or larger, which knocks roughly a third off the price. If your goal is purely lowest payback, panels usually beat batteries — check your system economics first with the Payback Calculator.
Questions
Frequently asked questions
How many kWh of battery do I need?
Multiply the daily energy you want to back up by the number of days of autonomy, then divide by usable depth of discharge. Backing up 10 kWh/day for one day with a 90% usable battery needs about 11 kWh. Essentials-only setups need ~8–13 kWh; whole-home backup with central AC needs 25–40 kWh.
Does a home battery qualify for the tax credit?
Yes. Battery storage of 3 kWh or larger qualifies for the 30% federal Residential Clean Energy Credit, even if you add it years after your panels. On a $11,000 battery that's a $3,300 credit, cutting the net cost to about $7,700.
Is a solar battery worth it in 2026?
It depends on your situation. Batteries are clearly worth it where outages are frequent, where time-of-use rates are steep, or where net metering is weak so self-consumption beats exporting. If your only goal is the fastest payback, panels alone usually win — a battery adds resilience and rate-arbitrage value more than pure savings.
How much does a solar battery cost?
In 2026, installed home batteries run about $1,000 per usable kWh before incentives, so a typical 10–13 kWh battery costs $10,000–$13,000, or roughly $7,000–$9,000 after the 30% federal credit. Larger whole-home systems with multiple units cost more.
How long do solar batteries last?
Modern lithium iron phosphate (LFP) home batteries are typically warrantied for 10 years and 6,000–10,000 cycles, retaining about 70% capacity at end of warranty. With daily cycling, expect 10–15 years of useful service.
Sarah has spent 12 years modeling US residential solar economics, including 4 years contributing to NREL's Distributed Generation Market Demand model. She holds a BS in Mechanical Engineering from UC Berkeley and reviews every calculator and state guide on GreenCalcs against current IRS, DSIRE and EIA data. Read our methodology →
