Solar battery storage: when it pays, and when it does not
Published 21 June 2026
A solar battery pays when the gap between your import and export rate is wide, usually 30 cents or more. At a 22-cent gap a 10 kWh system saves about €264 a year and takes 30–45 years to recover. Germany's 29-cent gap can pay back inside the 10-year warranty.
A solar battery earns money in one way: it moves power you generated at noon to the evening, so you use it yourself instead of buying it back from the grid. Whether that shift saves enough to recover the cost depends on a single number (the gap between what you pay to import a kilowatt-hour and what your utility pays you to export one). Get that gap right, and the rest of the arithmetic follows.
This post walks through the conditions that make a solar battery worth adding, the conditions that make it a waste of money, and the simple sum that tells you which situation you are in.
The import-export gap is the whole game
Say you import electricity at 30 cents per kWh and your export rate sits at 8 cents. Every kWh your battery lets you self-consume instead of buying back saves you the full 30 cents. The same kWh, sent to the grid without a battery, earned you 8 cents. The battery captures the 22-cent difference on each unit it shifts.
Now flip the tariff. You import at 25 cents and your utility pays you 20 cents to export under a generous feed-in deal. The battery captures 5 cents per kWh. You paid the same several thousand for the hardware, but it works against a gap one quarter the size. Payback stretches from under a decade to well past the battery's warranty.
The rule is this: a solar battery earns the spread, not the panels. The panels earn by displacing any import, whether or not a battery is attached. The battery earns only the extra margin between self-consumption and export. See also: how to read your solar payback, NPV and IRR and is solar worth it in 2026.
Where a solar battery pays
Three conditions push the gap wide enough to justify the cost.
Net metering is ending or was never available. For years, full net metering let you bank every exported kWh at the retail rate and draw it back later, which made a battery almost pointless because the grid served as a free, unlimited one. As utilities retire those schemes, the export rate collapses while the import rate holds. California's shift to NEM 3.0 cut export credits by roughly 75% for new solar customers (Solar Builder, 2022; effective April 2023), and a battery suddenly earns its keep there. The Netherlands' full net metering (salderingsregeling) ends 1 January 2027, after which the export rate drops sharply to a supplier-set "reasonable compensation"; estimates of that floor range from near-zero to roughly half the retail rate, and the final level is still being settled (Business.gov.nl, 2025). If your region is moving from net metering to net billing, run the numbers again; the economics may have flipped since your neighbour installed in 2021.
Your export rate is low. Germany's statutory feed-in tariff for new small systems sits at 7.78 ct/kWh (surplus rate, systems commissioned 2026, ADAC 2026) while households pay €0.37/kWh to import (BDEW 2026). That is a 29-cent gap. Australian feed-in rates have fallen to around A$0.05/kWh in most states (Solar Scorecard FiT 2026) against retail import prices of A$0.30–0.38/kWh depending on state. Wide gaps like these reward self-consumption, and a battery raises your self-consumption rate from around 30% of generation to 60–70%.
You face steep time-of-use peaks, or you want backup. If your evening rate spikes while solar floods the middle of the day at near-zero export value, the battery arbitrages that swing every night. Backup during outages carries real value too. Price it as resilience rather than savings, though, because a battery sized for blackouts is often larger than one sized for arbitrage alone.
Where a solar battery does not pay
You still have full or near-full net metering. The grid already acts as your free, unlimited battery. Adding a physical one buys you almost nothing until the scheme changes. Buy the panels, skip the battery, and revisit the decision when your utility revises the rules.
Your feed-in rate is high. Some legacy tariffs and a handful of current deals pay 15 cents or more to export. With a narrow gap to retail, the battery captures too little per cycle to recover its cost. You earn more by exporting freely.
Your evening demand is small. A battery only pays when you have evening load to absorb the stored energy. If you work away from home during the day, cook little after dark, and run no heat pump or EV charger overnight, the battery sits half-used and still cost full price.
Run the cycles, not the brochure
Installers quote total (nameplate) capacity. Your wallet cares about usable cycles over the life of the battery. Here are the three numbers to check before you sign anything.
| Number | What it means | Typical real-world value |
|---|---|---|
| Depth of discharge (DoD) | How much of nameplate capacity you can actually use | 80–100% (most modern LFP batteries reach 90–100%) |
| Round-trip efficiency | Energy out divided by energy in, accounting for conversion losses | 88–94% AC-to-AC for modern LFP; older or AC-coupled systems can fall to 85% (Sunlit Energy, 2026) |
| Cycle warranty | Guaranteed number of full charge-discharge cycles | 6,000+ cycles for modern LFP (BYD ~6,000; SolarEdge and Tesla Powerwall 3 warrant on capacity retention rather than a fixed cycle count) (SurgePV, 2026) |
A 10 kWh battery at 90% DoD gives you 9 usable kWh. At 90% round-trip efficiency, roughly 1 kWh is lost in every 10 you store. The saving per cycle is therefore 10% lower than the raw gap calculation suggests.
Here is the payback arithmetic that matters. Suppose your battery shifts 4 kWh of self-consumption on a typical evening across roughly 300 useful cycles per year, against a 22-cent import-export gap. That is 4 × 300 × €0.22 = €264 saved each year (use the calculator for your local currency). Installed battery costs vary by market: in Europe roughly €800–1,200 per usable kWh (SurgePV install cost data 2026; the €800/kWh default is a hardware baseline, so add installation and inverter integration to reach an all-in figure); in Australia roughly A$900–1,400/kWh; in the US roughly $900–1,300/kWh. A 10 kWh usable system in Europe therefore costs around €8,000–12,000 installed. Divide cost by annual saving and payback runs 30–45 years at a 22-cent gap, which is well beyond the 10-year warranty. Double the gap to 44 cents and payback falls to 15–22 years, marginal but improving.
Two further cautions. Winter cuts your cycling because there is less surplus solar to store. Battery capacity also degrades over time: a peer-reviewed field study of 21 residential systems in Germany found roughly 2–3% capacity loss per year (Figgener et al., Nature Energy, 2024), consistent with manufacturer warranty floors: Tesla Powerwall warrants 70% (US) or 80% (Europe) of original capacity at 10 years (Tesla Energy Library, 2024), while BYD Battery-Box warrants 60–70% depending on model and region. The battery you bought is not the battery you keep by year eight.
Tariff snapshots by market
The table below uses our modeled import and export rates as of mid-2026. These are point-in-time figures; tariffs revise quarterly or annually.
| Market | Import (approx.) | Export (approx.) | Gap | Battery case? |
|---|---|---|---|---|
| Germany | €0.37/kWh (BDEW 2026) | €0.078/kWh statutory surplus (ADAC 2026) | €0.29 | Yes, wide gap |
| Australia (national) | A$0.33/kWh (EnergyPlans 2026) | A$0.05/kWh (Solar Scorecard 2026) | A$0.28 | Yes, plus federal battery rebate ~A$240–270/usable kWh on the first 14 kWh, declining above that (Clean Energy Regulator 2026) |
| UK (typical SEG) | £0.28/kWh (Ofgem Q1 2026) | £0.12–0.15/kWh typical flat rate (Which? 2026) | £0.13–0.16 | Marginal; check your actual offer |
| California (NEM 3.0) | $0.332/kWh | ~$0.06/kWh avoided cost (Aurora Solar 2026) | $0.27 | Yes; NEM 3.0 makes battery near-essential for new solar |
| Netherlands (post-2027 forward) | €0.27/kWh | ~€0.07/kWh blended forward (net metering ends Jan 2027) | €0.20 and widening | Strong case for 2026 installs |
| UK best SEG (Octopus/Good Energy) | £0.28/kWh | £0.23–0.25/kWh (Solar Foundry 2026) | £0.03–0.05 | No; gap too narrow, export freely |
How we handle the maths
We model your roof on free, resale-permitted government data. PVGIS covers European irradiance; NASA and NREL datasets cover everywhere else. Your actual sun hours, not a sales brochure average, drive the estimate. We show the panel payback, the battery payback, the NPV and the IRR side by side. When the battery loses money against your local tariff, we say so plainly. You see a ballpark before you share any contact details.
For a deeper look at the panel economics that underpin this, see how much do solar panels cost in 2026 and solar payback, NPV and IRR explained.
Decide on the panels first. Add the battery only when the gap, your evening load, and the warranty period all line up.
Frequently asked questions
When does a solar battery pay back its cost?
It depends on your import-export gap and how much you cycle the battery. With a 22-cent gap and 4 kWh shifted per day across 300 days, you save roughly €264 a year. At €800–1,200 per usable kWh installed, a 10 kWh system costs €8,000–12,000. Payback runs 30–45 years at that gap. A gap of 30 cents or more makes the case much stronger.
Is a solar battery worth it in Germany?
Germany has one of the strongest battery cases in Europe. The statutory surplus feed-in rate sits at €0.078/kWh (2026, ADAC), while import costs €0.37/kWh (BDEW 2026), a 29-cent gap. With a reasonably sized system and moderate evening load, payback can land inside the battery's 10-year warranty.
Does a solar battery make sense in the UK?
It depends which Smart Export Guarantee rate you can get. At the best rates (up to ~£0.25/kWh on the best install-linked or time-of-use export tariffs), the import-export gap can be just 3–5p, too narrow to justify a battery on savings alone. At a typical flat rate of 12–15p, the gap widens to 13–16p and the case improves. Check your actual export offer before buying.
How long do home batteries last?
Most quality LFP (lithium iron phosphate) batteries carry warranties of 4,000–6,000+ cycles or 10 years, whichever comes first (SurgePV 2026). At one full cycle per day, that is 11–16 years to reach the cycle limit. In practice most batteries hit the calendar warranty first. Capacity typically falls to 70–80% of original by end of warranty.
Should I add a battery to my existing solar panels?
Run the import-export gap calculation first. If your export rate has dropped since you installed (as it has in Germany, Australia, and California), retrofitting a battery can make sense. If you still have full net metering at near-retail rates, the grid is already acting as your battery for free. Wait until your tariff regime changes.
See also: charge your EV with solar, a related use case where a battery or smart EV charging captures more of your surplus. And solar inverters explained, because a battery retrofit requires inverter compatibility.
Estimate only, not a quote. Figures use local climate data and average tariffs; your installer's quote will be exact.
The economics of going solar
Keep reading
See the honest numbers for your roof
Free, no sign-up. Your address → payback, NPV, incentives and a 25-year cashflow on real climate data. An estimate, not a sales quote.
Calculate my solar savings →