A home battery proposal can look complete while leaving important questions unanswered: which loads work during an outage, how much energy is available when it begins, and which supporting work is included in the price? Start with one common outage brief for every provider.
This free checklist is for preparing a comparison, not sizing a system or approving an installation. A health or safety requirement needs an appropriate professional contingency plan; a generic runtime illustration cannot establish continuous service.
Ask what the backup promise covers
Name the services you want, the desired outage period and any loads you can defer. Ask which circuits or equipment the actual proposal covers. Tesla's manufacturer-specific backup guide distinguishes partial-home and whole-home backup and refers final detailed design to a qualified provider. Do not treat one manufacturer's statement as proof of another product's capability.
Keep kW and kWh in separate columns
The DOE's Solar-Plus-Storage 101 explainer illustrates power capability and stored-energy duration as different dimensions. It was published March 11, 2019; use that terminology background, not its old utility-scale cost figures as today's home-battery prices.
A kWh label alone does not explain simultaneous loads or starting demand. Ask for continuous and temporary power capability, duration conditions and compatibility evidence in the proposed configuration.
Free provider comparison checklist
Copy these rows into your notes with columns for Provider A, Provider B, evidence and the next question. Keep unknowns visible.
- Covered service: selected loads, circuits, desired period and exclusions.
- Power: continuous, temporary and starting-load capability confirmed by the provider.
- Energy: nominal, usable stored or AC-available kWh; state which boundary is quoted.
- Starting condition: assumed charge when the outage begins and adjustments already included.
- Recharge: whether solar can operate in the outage, how much energy is assumed and when it arrives.
- Complete price: battery, controls, installation, applications, supporting work, allowances and ongoing charges.
- Responsibilities: qualified assessment, applicable approvals, warranties, service and handover records.
Try a conditional duration check
Original invented example: 8.40 kWh is assumed available to AC loads. With a constant 0.70 kW load, no recharge and compatible power capability, 8.40 ÷ 0.70 = 12 hours. At 1.40 kW, the same energy gives 6 hours. Neither result predicts a real home's outage duration.
The California Air Resources Board backup tool explains the power/energy arithmetic and warns that generic assumptions do not determine household demand. Its discussion also identifies starting loads and variable solar contribution. Ask your provider for home-specific evidence rather than substituting a generic appliance list.
Do not subtract the wrong reserve
A reserve saved for backup may become available during the outage, while a protected operating floor may remain unavailable. Tesla's Backup Reserve explanation explicitly says its reserve becomes available during an outage. Other products need their own documentation. This is a reason to ask about the energy boundary, not an instruction to change a setting.
If the provider's AC-available energy figure already includes conversion and operating-floor treatment, applying the same reductions again would count them twice. Keep each adjustment and its source visible.
Compare complete scope, then uncertainty
A battery-only headline and a complete installed backup package are different offers. Ask the provider to identify the appropriate conversion/control equipment, installation, supporting work and approvals for your actual home. These are questions for qualified professionals; this article supplies no installation procedure or local code determination.
Keep provisional amounts separate from fixed charges. Request a no-recharge scenario and a separately supported recharge scenario. Daily energy totals alone do not prove energy arrives before a load needs it. Do not deduct an unverified incentive or future saving from the gross commitment.
Leave with a specific next question
A useful comparison can end with 'confirm which starting event this proposal supports' or 'provide the omitted controls cost.' Record who must answer and which revised document closes the gap.
The free contractor quote comparison tool supports general scope checks. The Home Battery Backup Budget Planner adds four complete hypothetical cases, seven reusable worksheets, 35 fillable fields and two completed demonstrations across 26 pages for £9.99 GBP. It focuses on outage-service and budget records; the existing solar book covers broader solar-offer questions. Buying either is optional.
Primary links checked October 28, 2026. All examples and worksheet demonstrations are invented teaching material. Sources do not endorse HomeCostEngine. No current local market price, actual reader outcome, guaranteed runtime, savings or validated purchase demand is claimed.