Hybrid Solar System Calculator

Size a grid-tied hybrid solar system: PV array kW, battery kWh, hybrid inverter capacity, and annual self-consumption.

Battery & array assumptions

Depth of discharge and round-trip efficiency default to typical values for the battery chemistry you select, and can be overridden. Performance ratio (80% by default) covers inverter conversion, wiring, soiling, and temperature losses between the panel's rated output and what actually reaches your loads.

By · Energy analysts and engineers documenting every formula, source, and limitation behind our calculators.

Published Formula, sources & limitations

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HOW IT WORKS

How does the hybrid solar system calculator work?

The calculator solves three connected sizing problems — the PV array, the battery bank, and the hybrid inverter — from your daily energy use, local sun resource, and how much load you want backed up during an outage.

1

Enter use, sun & offset

Set your daily home energy use, local peak sun hours, and what share of your bill you want solar to cover.

2

Set your backup needs

Choose the load you want kept running during an outage, for how many hours, and your battery chemistry.

3

View your system sizes

See the PV array, battery, and inverter sizes, plus annual output, self-consumption, and export.

Why a hybrid system is sized in three connected steps

A grid-tied hybrid system has to satisfy three separate jobs at once, and each one drives a different component. The PV array is sized to hit your annual bill-offset target, using your daily use, local sun hours, and a performance ratio that accounts for real-world losses. The battery is sized independently, from the load you want backed up and for how long — it doesn't need to be big enough to store a whole day of solar production, only enough to ride out the outage duration you actually care about. The hybrid inverter then has to be rated for whichever of those two is larger, since it's the single component that both converts the array's DC output and powers your backed-up circuits.

THE CALCULATIONPV array (kW) = (daily use × bill offset %) ÷ (peak sun hours × performance ratio)

Battery usable (kWh) = backed-up load × backup duration. Nameplate = usable ÷ (depth of discharge × round-trip efficiency). Inverter (kW) = larger of the array size or backed-up load, ×1.05 headroom.

Worked example: a full-offset home with a half-day of backup

EXAMPLE 1

30 kWh/day, 4.5 peak sun hours, 100% bill offset, lithium battery backing up 5 kW for 6 hours

Say your home uses 30 kWh a day, your area averages 4.5 peak sun hours, and you want solar to fully offset your annual bill. You want a lithium battery that can carry your fridge, well pump, and some outlets — a 5 kW backed-up load — for 6 hours during an outage, and you're using the default 80% performance ratio, 90% depth of discharge, and 95% round-trip efficiency.

  1. PV array: (30 kWh × 100%) ÷ (4.5 h × 0.80) = 30 ÷ 3.6 ≈ 8.3 kW.
  2. Battery usable: 5 kW × 6 h = 30 kWh.
  3. Battery nameplate: 30 ÷ (0.90 × 0.95) ≈ 35.1 kWh.
  4. Hybrid inverter: larger of 8.3 kW and 5 kW, ×1.05 ≈ 8.8 kW.
  5. Annual PV output: 8.3 kW × 4.5 h × 365 × 0.80 ≈ 10,950 kWh.

With 30 kWh of usable battery matching a full day's use, self-consumption lands around 95% — most of what the array produces gets used on-site rather than exported, leaving about 548 kWh exported to the grid over the year.

Result: about an 8.3 kW array, a 35.1 kWh lithium battery (30 kWh usable), an 8.8 kW hybrid inverter, and roughly 10,950 kWh of annual production at 95% self-consumption.

Worked example: a smaller array with lead-acid storage

EXAMPLE 2

20 kWh/day, 5.5 peak sun hours, 120% bill offset, AGM battery backing up 3 kW for 10 hours

Now suppose a smaller household uses 20 kWh a day in a sunnier location averaging 5.5 peak sun hours, and wants a 120% bill offset to leave room for an EV purchase next year. They're backing up a lighter 3 kW load — enough for a fridge and lighting — for a longer 10-hour outage, using an existing AGM lead-acid bank at 50% depth of discharge and 85% round-trip efficiency, with a 78% performance ratio for an older inverter.

  1. PV array: (20 kWh × 120%) ÷ (5.5 h × 0.78) = 24 ÷ 4.29 ≈ 5.6 kW.
  2. Battery usable: 3 kW × 10 h = 30 kWh.
  3. Battery nameplate: 30 ÷ (0.50 × 0.85) ≈ 70.6 kWh — more than double Example 1's, for the same usable energy, because lead-acid tolerates far less depth of discharge.
  4. Hybrid inverter: larger of 5.6 kW and 3 kW, ×1.05 ≈ 5.9 kW.
  5. Annual PV output: 20 kWh × 120% × 365 ≈ 8,760 kWh.

Result: about a 5.6 kW array, a 70.6 kWh AGM battery (30 kWh usable), a 5.9 kW hybrid inverter, and roughly 8,760 kWh of annual production at 90% self-consumption.

Understanding each result

PV array (kW DC) is the panel nameplate capacity needed to hit your bill-offset target, given your sun hours and performance ratio.

Battery nameplate and usable (kWh) separate what's printed on the battery from what you can actually draw. Usable capacity is driven purely by your backup load and duration; nameplate scales that up based on your chemistry's depth-of-discharge limit and round-trip efficiency.

Hybrid inverter (kW) is the continuous AC rating needed to handle the larger of your array's output or your backed-up load, with headroom so it isn't running at its ceiling.

Annual PV output (kWh) is what the sized array is expected to generate over a year — by construction, this tracks your daily use and bill-offset target directly, since that's exactly what the array was sized to hit.

Self-consumption (%) and annual grid export (kWh) describe how that output gets used. A battery sized to cover a meaningful share of your daily use shifts more midday solar surplus into evening use instead of exporting it, which is why self-consumption rises with battery size relative to daily use, up to a realistic ceiling.

Why annual output depends only on daily use and bill offset

You might notice the annual PV output figure doesn't change if you adjust sun hours or performance ratio on their own — only if you change your daily use or offset target. That's not a coincidence: this calculator first sizes the array specifically to hit your chosen offset target given those same sun-hour and performance-ratio assumptions, so they cancel out of the annual-output figure by construction. A lower performance ratio or fewer sun hours produces a physically larger array, not a smaller annual output — the array simply needs more panels to deliver the same energy target under weaker conditions.

Sizing the battery for backup, not for storage

It's a common assumption that a hybrid battery should store a full day of solar production, but that's usually oversized and expensive for what most homeowners actually want. This calculator instead sizes the battery for a specific backup scenario — a chosen load, for a chosen number of hours — which is typically a fraction of total daily use. If you want the battery to also meaningfully raise your self-consumption rate, increase the backed-up load or duration so its usable capacity approaches your full daily use, as in Example 1 above.

Common ways to use this calculator

Scoping a new hybrid install

Get a starting PV, battery, and inverter size before requesting quotes from installers.

Comparing battery chemistries

Switch between lithium, AGM, and flooded to see how nameplate capacity and cost scale with depth of discharge.

Right-sizing backup power

Adjust backed-up load and duration to see the battery cost of backing up more or less of your home.

Planning for future load growth

Set a bill offset above 100% to leave headroom for an EV or home addition.

Privacy and appropriate use

Your inputs are processed directly in your browser and are not sent to a database. This is a planning-stage estimate for component sizing, not an engineering, permitting, or utility-interconnection document — have a licensed solar installer verify final equipment selection, wiring, and code compliance for your specific site.

Size your hybrid system ↑Browse all calculators →
FREQUENTLY ASKED QUESTIONS

Questions about the hybrid solar system calculator.

Clear answers about bill offset, battery chemistry, backup sizing, and self-consumption.

What's the difference between a hybrid and a standard grid-tied system?

A standard grid-tied inverter only sends solar power to your home and the grid — if the grid goes down, it shuts off for safety, even on a sunny day. A hybrid inverter adds a battery connection and an automatic transfer switch, so it can island itself from the grid during an outage and keep a chosen set of "backed-up" circuits running from stored battery power.

What does "bill offset target" mean?

It's the share of your annual electricity use you want the solar array to generate, expressed as a percentage. 100% means the array is sized to produce roughly as much energy over a year as your home consumes. Going above 100% builds in headroom for panel degradation, an EV you plan to add later, or a home addition; going below it sizes a smaller, less expensive array that only offsets part of your bill.

Why is the battery's nameplate capacity bigger than its usable capacity?

Nameplate (or rated) capacity is what's printed on the battery; usable capacity is what you can actually draw before hitting the depth-of-discharge limit that protects the battery's lifespan, further reduced by round-trip efficiency losses during charging and discharging. A 30 kWh usable requirement needs roughly 35 kWh of nameplate lithium capacity at 90% depth of discharge and 95% round-trip efficiency — and closer to 70+ kWh nameplate for lead-acid chemistries, which tolerate far shallower discharge.

Why does the hybrid inverter's rating exceed the PV array size?

The inverter has to handle whichever is larger: the array's full DC output, or the backed-up load it needs to power during an outage — plus a margin so it isn't running at its absolute ceiling under normal conditions. This calculator takes the larger of the two and adds 5% headroom, then rounds to a buildable size.

How is self-consumption different from bill offset?

Bill offset compares your array's total annual output to your total annual use. Self-consumption measures what share of the solar energy you generate is actually used on-site — by your loads directly, or by charging the battery — rather than exported to the grid. A bigger array relative to your load tends to lower self-consumption without storage, because more midday production exceeds what the house can use in real time; a battery raises self-consumption by shifting that midday surplus to evening and overnight use.

Which battery chemistry should I choose?

Lithium (LiFePO₄) is the standard choice for new hybrid installs — it tolerates 80–90% depth of discharge, has a longer cycle life, and needs less maintenance. AGM and flooded lead-acid cost less upfront but need roughly double the nameplate capacity for the same usable energy, since they're typically limited to 40–50% depth of discharge, and flooded batteries also need regular watering and ventilation.

How much backup should I plan for?

Start with the loads you actually need during an outage — refrigerator, well pump, some lighting and outlets, internet — rather than backing up the whole panel, since whole-home backup requires a much larger and more expensive battery. Add up those loads' running wattage for "backed-up load," and set "backup duration" to how many hours of outage you want to ride through before the battery would need solar recharge or a generator.

Does this account for net metering or export compensation?

No — this calculator sizes hardware and estimates the physical annual export in kWh, not its dollar value. Export compensation varies enormously by utility and state, from full retail net metering to low avoided-cost rates. Once you have an export estimate here, a feed-in tariff or net-metering calculator can convert it to a dollar figure using your utility's actual rate.

Is this a substitute for a professional system design?

No. This is a planning-stage estimate to help you scope a system and have an informed conversation with an installer. A licensed solar installer will account for your roof's actual usable area and shading, local code and utility interconnection requirements, specific equipment datasheets, and your utility's export rules — all of which can shift the final design from this estimate.

Is my data stored?

No. All inputs and calculations run directly in your browser and are not sent to a server or saved in an account. General site usage may be measured through Google Analytics as described in our Privacy Policy.