Generation, self-consumption, and export value
Generation is split into energy used on site and energy exported. Energy value combines avoided imports and export credits at your entered prices. It is not a complete bill forecast or a return-on-investment calculation. A known on-site solar amount must not exceed estimated period generation. A zero-generation period reports a zero on-site share. Currency selects a label without conversion.
For an electric vehicle’s energy requirement, the EV Charging Calculator estimates charger-side kWh between two charge levels.
The formula
Peak sun hours express daily irradiation as an equivalent number of hours at reference full-sun intensity. The combined loss factor reduces the theoretical nameplate output once. Self-used and exported energy are then valued at their separate rates.
Worked example
A 5 kW array with four peak sun hours and 20% combined losses averages 16 kWh daily, or 480 kWh in thirty days. At 70% self-use, 336 kWh offsets imports and 144 kWh is exported. Prices of 0.20 and 0.05 give an estimated energy value of 74.40. Ten equal 500 W panels give the same 5 kW capacity. Known on-site solar use of 11.2 kWh/day for 30 days gives the same 336 kWh, 70% share and 74.40 USD value.
How to use this calculator
- Enter the complete DC array capacity in kW or W, or multiply an equal-panel count by each panel’s watt rating.
- Enter peak sun hours, combined losses and days for the same period. Choose on-site solar use as a share or a known period/daily energy amount.
- Enter import and export tariffs in matching price and currency units. Review generation, on-site use, exports and energy value.
Daylight hours are not peak sun hours
A long summer day does not provide full rated output for every daylight hour. Solar-resource data incorporates changing sunlight intensity. Orientation, shading, weather, and season all matter. Use a site-specific resource estimate for the relevant period rather than treating the example as a universal climate assumption.
When to use a detailed solar model
This calculation applies a single resource figure and one loss factor; it does not retrieve weather or model an inverter hour by hour. Tools such as PVWatts provide a more detailed location-based analysis. If multiple independent losses are known, combine their remaining fractions instead of blindly adding percentages. Include inverter effects only once when choosing the combined allowance here.
Solar used on site differs from household demand
A household energy bill includes electricity imported from the grid and cannot by itself establish how much solar was used on site. Enter a solar self-consumption measurement or assumption for the same period. This tool does not infer that quantity from total consumption or match loads hour by hour. Switching daily and period energy converts the entry; changing the number of days while daily entry is selected keeps that daily amount fixed.
Assumptions & limitations
What this calculation assumes
- The input resource and loss factors represent an average over the selected period.
What to keep in mind
- No hourly clipping, battery dispatch, tariff tiers, installation cost, or guaranteed savings.
Common questions
Does the result include a battery?
No. Enter solar used on site as a share or a known energy amount. Storage losses, charging schedules and battery capacity require a separate model.
Can I multiply one sunny month by twelve?
That can overstate annual generation. Use a representative annual-average resource value or calculate seasonal periods separately.
Sources & further reading
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