Start with the project, then the price
A simple on-roof installation, an in-roof system during a renovation and a commercial roof project can require very different work. Access, roof condition, electrical upgrades and equipment location all affect the quotation. A price copied from another installation is a starting point for a conversation, not a reliable budget for yours.
Jelvis assesses projects across West Sussex and surrounding areas. Tell us the installation address, your current electricity use and whether you are planning an EV, electric heating or other changes. If you do not know your annual usage, a recent bill or an approximate monthly spend can help us begin.
Compare system sizes correctly
Panel capacity is usually expressed in kWp. For example, twelve 450 W panels have a combined rated capacity of 5.4 kWp. That is a rating under test conditions; it is not a promise of continuous output or a forecast of annual generation.
Your proposal should explain the expected generation for the actual layout, including orientation and shading. Battery storage is a separate decision. Compare its usable energy, charging and output limits, compatible inverter and installation requirements, rather than choosing on the largest kWh figure alone.
What a clear quotation should explain
- The proposed panel layout and exact panel, inverter and battery models.
- Roof mounting method, access equipment and any roof work included.
- Electrical connections, cable routes, protection and any supply upgrades.
- The grid-connection process and any export limitation assumptions.
- Testing, commissioning, monitoring setup and handover documents.
- Warranty terms, exclusions, payment stages and the treatment of any applicable tax.
Ask whether scaffolding, bird protection, alterations to the consumer unit and backup equipment are included or optional. These details can explain a price difference that initially looks hard to justify.
Keep the savings assumptions visible
Electricity you use directly and electricity you export have different values. A forecast should show the import and export rates used, how much generation is expected to be used on site and what changes when a battery is added. Future tariffs, usage and equipment performance can change.
Once you have a project-specific generation estimate, our solar PV savings calculator can illustrate the annual electricity value using figures you enter. It does not calculate installation payback or replace a design assessment.
Compare options with the same scope
Ask for solar PV alone and solar PV with storage if you want to see the difference. If backup is important, state which loads you want supported. A standard battery installation does not automatically supply the whole building during a power cut.
Browse our equipment guide and roof mounting options before enquiring, or let us recommend an approach. We will confirm the proposed equipment and scope in your quotation; this guide is not a fixed-price offer.
Further reading: Energy Saving Trust: solar PV costs and benefits.