Your numbers
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Your solar production
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Conversion loss assumptions
Battery & storage
AC coupled vs DC coupled sizing tool
Enter your daily solar production. See how much usable energy each battery architecture delivers after their different conversion losses.
How it works
Three steps to comparing coupling architecture
Step 1
Know your typical daily solar production
Check your solar monitoring app or utility production data for a typical day's total, or use the charge time from solar tool to model it.
Step 2
Compare the efficiency gap
DC coupling typically delivers slightly more usable energy from the same solar production, thanks to one fewer conversion step.
Step 3
Weigh efficiency against other factors
Retrofit compatibility with existing equipment often matters more than the efficiency gap for many installations. The battery inverter pairing tool is a useful next check.
Understanding AC coupled versus DC coupled systems
Why the extra conversion step in AC coupling matters
AC coupled systems convert solar's native DC power to AC through the solar inverter first, then convert it back to DC a second time through a separate battery inverter to actually charge the battery, an extra round of conversion that DC coupled systems skip entirely, a difference NREL's technology baseline research quantifies as roughly 85% round trip efficiency for AC coupled charging versus 87% for DC coupled. DC coupled systems instead charge the battery directly from DC solar power through a charge controller, avoiding one full conversion cycle and its associated losses, a process explained in the Department of Energy's inverter basics guide. From the same 10 kWh of solar production, this typically translates to DC coupling delivering roughly 0.2 to 0.3 kWh more usable energy than AC coupling.
Why AC coupling remains common despite the efficiency gap
AC coupling is often significantly simpler to retrofit onto an existing grid-tied solar installation, since it doesn't require replacing or modifying the existing solar inverter, just adding a separate battery and battery inverter alongside it. This makes AC coupling the practical choice for many homeowners adding battery storage to solar they already own, even though a from-scratch installation might favor DC coupling's efficiency advantage. AC coupling can also offer more flexibility mixing equipment from different manufacturers, an option worth weighing against the battery inverter pairing tool. The Department of Energy's inverter basics guide publishes the reference data behind this estimate.
Why the efficiency difference is modest, not dramatic
While DC coupling is more efficient, the actual gap between the two architectures is a few percentage points, not a transformative difference in system performance. For most homeowners, equipment compatibility, installer experience with a given architecture, and total system cost end up mattering more in the final decision than this efficiency gap alone, a cost comparison the quick financing comparison tool in our Financing category can help weigh alongside an installer's quote. The round trip efficiency calculator covers the broader efficiency picture that applies regardless of coupling architecture.
What to do with this number next
Discuss both architecture options with your installer, weighing this efficiency comparison against your specific situation, including whether you have existing solar equipment to retrofit around. The charge time from solar tool is a useful next step regardless of which architecture you choose. For the inverter equipment side of this decision, the hybrid inverter sizing calculator in our Inverters & Equipment category covers hardware selection in more depth.
Questions
Frequently asked
From the same 10 kWh of solar production, a DC coupled system delivers about 9.85 kWh after conversion losses, while an AC coupled system delivers about 9.6 kWh, a roughly 0.25 kWh difference from the extra conversion step in AC coupled architecture.
AC coupled systems convert solar DC power to AC through the solar inverter, then back to DC to charge the battery through a second inverter, an extra conversion step that DC coupled systems skip by charging the battery directly from DC solar power through a charge controller.
AC coupling is often simpler to retrofit onto an existing grid-tied solar system, since it doesn't require replacing the existing solar inverter, and it can offer more flexibility connecting multiple different equipment brands together.
For a brand new installation without existing solar equipment to work around, DC coupling's efficiency advantage is worth considering, though it's a modest percentage difference rather than a dramatic one, and other factors like equipment compatibility and installer experience often weigh more heavily in the final decision.