1. The appliances and loads are clearly listed

A quotation should not be based only on the size of your house. Two three-bedroom homes can have completely different energy needs. One may require only lights, Wi-Fi, television and a fridge during an outage. Another may include a water pump, microwave, kettle, washing machine, cooker or home office equipment.

Ask for a load schedule showing the appliances, wattages, quantities and expected operating hours. This is the foundation of the entire design.

2. The proposal separates running load from start-up surge

Some appliances require more power when starting than when running normally. Fridges, pumps, freezers, compressors and air conditioners are common examples. An inverter may appear large enough based on normal wattage but still trip when a motor starts.

The supplier should confirm both the expected simultaneous running load and the largest start-up surge. The inverter must be selected to handle both.

3. The battery capacity is stated in usable energy

Battery descriptions can be misleading when they only show voltage and amp-hours. What matters to you is how much usable energy the battery can deliver and how that translates into backup time.

Ask for the nominal battery capacity in kilowatt-hours, the recommended usable depth of discharge and the estimated backup duration for your selected appliances. Backup time should be tied to a stated average load, not a vague promise such as “powers a three-bedroom house.”

4. The solar-panel array matches the energy target

Panels are needed to replace the energy consumed and recharge the battery. The quotation should explain the total panel capacity, expected daily generation, roof-space requirement and any assumptions about sunlight, orientation and shading.

A large inverter with too few panels may leave the battery undercharged. Too many panels can also be a problem if the inverter’s solar-input limits are ignored.

5. The equipment specification is complete

Do not accept generic descriptions such as “5 kW inverter” or “lithium battery.” The quotation should identify the manufacturer, model, rating and important technical characteristics of the proposed equipment.

It should also include the balance-of-system items: mounting structures, isolators, breakers, surge protection, cables, earthing, changeover arrangements, distribution-board work, monitoring and installation accessories.

6. Warranties and after-sales responsibilities are written down

Ask for separate warranty information for the inverter, battery, panels and installation workmanship. Confirm who will process warranty claims, how long troubleshooting takes and whether transport or technician costs may apply.

A manufacturer warranty is valuable only when the supplier can support the claim process and the equipment has been installed correctly.

7. The payment and completion terms protect you

The quotation should state the deposit, balance-payment milestones, installation timeline, testing process and documents you will receive at handover. Avoid paying the full amount before installation and commissioning unless there is a clear contractual reason.

Confirm whether the final handover includes user training, system settings, manuals, warranties, as-built information and completion documentation.

What to do when the quote is unclear

Do not be pressured into paying immediately because a discount is expiring or equipment is supposedly running out. Ask the supplier to answer the missing questions in writing. A professional supplier should be able to explain the design without becoming defensive.