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Solar Self-Consumption Calculator

Find your self-consumption ratio, see the battery impact, and maximize the value of your solar production.

Solar production
kW
kWh/day
Usage pattern (% of daily consumption)
%
%
%
%
Battery & rates
kWh
$/kWh
$/kWh
Self-consumption ratio (without battery)
45.0%
Self-consumption (with battery)45.0%
Grid export per day17.6 kWh
Grid import per day17.6 kWh
Annual self-consumed value$788
Annual export value$385
Total annual savings (no battery)$1,174
Total annual savings (with battery)$1,174
Optimal battery for 80% self-consumption14 kWh
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How to Use This Calculator

Enter your solar production

Input your system size (kW) and daily solar production (kWh). If you don't know your daily production, estimate it as: System kW × Peak Sun Hours × 0.86. For example, an 8 kW system in a 5-hour sun area produces about 34 kWh/day.

Set your usage pattern

Enter what percentage of your daily electricity consumption falls in each 6-hour period. These percentages must sum to 100%. This is the most important input — a work-from-home household using 35% of electricity in the afternoon (when solar peaks) gets dramatically better self-consumption than a household where 70% of usage happens evenings and nights.

Understand the results

The calculator shows your self-consumption ratio — the percentage of solar production you use directly (not exported). Higher is better when your retail rate exceeds your feed-in tariff. The battery comparison shows how adding storage improves self-consumption, and the optimal battery size recommendation tells you the minimum battery to reach 80% self-consumption.

The Formula

Solar Production per Period: Morning 15%, Afternoon 60%, Evening 25%, Night 0% Direct Self-Consumption per Period = min(Solar Production, Load Consumption) Surplus per Period = max(0, Solar Production - Consumption) Deficit per Period = max(0, Consumption - Solar Production) Self-Consumption Ratio (no battery) = ∑Direct / Total Daily Production × 100% Battery can absorb Surplus, discharge into Deficit periods (95% round-trip efficiency) Self-Consumption Ratio (with battery) = (∑Direct + Battery Discharge used) / Total Production × 100% Annual Self-Consumed Value = Annual kWh Self-Consumed × Retail Rate Annual Export Value = Annual kWh Exported × Feed-in Tariff

The solar production profile used (15% morning, 60% afternoon, 25% evening) is a realistic average for a south-facing array at 30° tilt. North-facing or east/west arrays will shift this distribution.

Example

9-to-5 worker vs work-from-home — same 8 kW system

Two neighbors both have 8 kW solar systems producing 32 kWh/day. Electricity rate: $0.15/kWh, feed-in tariff: $0.06/kWh.

WFH daytime usage (40% afternoon)Self-consumption ~52%
9-to-5 worker (10% afternoon)Self-consumption ~28%
WFH annual savings~$2,100
9-to-5 annual savings~$1,600
WFH with 10 kWh batterySelf-consumption ~71%
9-to-5 with 10 kWh batterySelf-consumption ~65%

The work-from-home household saves $500 more per year with no battery — simply because their usage pattern aligns with solar production. The 9-to-5 worker benefits more from battery storage: adding 10 kWh raises their self-consumption from 28% to 65%, adding ~$300/year in savings on top of the solar savings.

FAQ

Solar self-consumption is the percentage of your solar electricity that you use directly in your home, rather than exporting to the grid. If your 10 kWh/day system produces 10 kWh and you directly use 6 kWh while exporting 4 kWh, your self-consumption rate is 60%. Self-consumption is distinct from self-sufficiency (the share of your total consumption covered by solar). High self-consumption means more of your solar output is valued at retail electricity rate rather than the lower feed-in tariff rate.
In most markets, the retail electricity rate ($0.12–$0.30/kWh) is 2–5x higher than the feed-in tariff ($0.03–$0.08/kWh). Every kWh you self-consume instead of export is worth 2–5x more financially. In California under NEM 3.0, the export rate dropped to ~$0.05/kWh while retail rates are $0.25–$0.35/kWh — making self-consumption 5–7x more valuable than export. In this environment, maximizing self-consumption through behavior changes and battery storage is critical to solar ROI.
The optimal battery size depends on your usage pattern. For a 9-to-5 household that consumes 60% of electricity in the evening/night, a battery sized to cover that evening deficit is ideal. Diminishing returns kick in around 80–90% self-consumption — going from 80% to 95% requires disproportionately large battery capacity. A rule of thumb: battery size (kWh) should roughly equal your evening + night electricity consumption. For most homes, 10–15 kWh achieves 70–85% self-consumption.
If your feed-in tariff is close to your retail rate (e.g., full retail net metering), it doesn't matter — every kWh is worth the same. If your feed-in tariff is significantly lower (most US markets today, Australia, UK), prioritize self-consumption. If your feed-in tariff is higher than retail (rare, some German/Italian legacy programs), maximize export. Check your current utility tariff structure before optimizing.
Shift load to daytime: run dishwasher, washing machine, and dryer during peak solar hours (10am–3pm). Pre-heat or pre-cool your home while solar is generating (HVAC is typically 30–40% of home load). Charge an EV during midday hours. Install a solar diverter to heat a hot water cylinder with excess solar instead of exporting. Add a battery for larger load shifts. Smart home automation (Home Assistant, SolarEdge Home Control, Tesla Energy Plan) can automatically manage these shifts based on solar forecast.

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