A Net Billing quotation cannot be priced from kW alone. Identical array ratings can require different mounting, cable routes, protection, access work and switchboard changes. Compare the complete scope, not just a headline price per installed kW.
What a complete quotation includes
- Panels, inverter, mounting and DC/AC cabling with identified models.
- Protection, earthing, metering and monitoring.
- Design, installation, commissioning and handover documentation.
- Separate options for batteries, backup circuits and additional work.
- Taxes, connection items, maintenance and clearly identified exclusions.
Ask whether the production estimate includes shading, system losses and export restrictions. A cheaper offer is not directly comparable if it omits work required to operate the installation.
Estimating annual benefit
A simplified model is: benefit = directly consumed kWh × avoided variable energy cost + exported kWh × export value − annual operating costs. Do not assume fixed or unavoidable bill components disappear. With batteries, model conversion losses and degradation separately and never count the same stored kWh as both direct consumption and export.
Explicitly hypothetical example
Assume an investment of €12,000, direct use of 8,000 kWh/year, exports of 4,000 kWh/year and operating costs of €150/year. Energy values of €0.20/kWh and €0.05/kWh are illustrative assumptions only. They are not current market tariffs or contracted export rates.
| Calculation | Illustrative result |
|---|---|
| Direct use | 8,000 × 0.20 = €1,600/year |
| Exports | 4,000 × 0.05 = €200/year |
| Simple net annual benefit | 1,600 + 200 − 150 = €1,650/year |
| Simple payback | 12,000 / 1,650 ≈ 7.3 years |
Simple payback ignores financing, discounting, declining output and replacements. It is not a guarantee. Reduced self-consumption or additional installation costs increase the period; a more complete cash-flow model should include these effects.
Compare scenarios before deciding
Request conservative, central and favourable cases using a consistent method. Change yield, self-consumption, energy values and operating costs independently. If the proposal works only in the favourable case, reconsider system size or storage before committing. Also distinguish nominal cash flows from inflation-adjusted cash flows when comparing long-term outcomes.
Verify current connection information with HEDNO and use the actual supply and export contracts for the financial inputs. Our Net Billing service and commercial solar assessment start with your measured load profile.
Compare on the same basis
Two quotations are not comparable if one includes design, protection devices, monitoring, civil works and commissioning while the other lists panels and inverter alone. Make an included/excluded table for equipment, installation, connection work, maintenance and potential component replacement. Ask which costs were verified by a site survey.
For payback, compare conservative, base and favourable scenarios using consistent consumption assumptions. Changing both the electricity price and generation at once obscures which assumption drives the result. The outcome is an estimate, not a guaranteed capital recovery date.
Discuss your installation
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