Plan home solar before you collect sales quotes

Start with the household, not the hardware

The Department of Energy’s planning guidance begins with energy efficiency, local codes and requirements, site resources, system size, economics, and installer selection. That order matters. A proposal cannot be meaningfully sized until you understand current use and likely changes.

Collect at least twelve months of electricity usage in kilowatt-hours, not just cost. Note planned changes such as an electric vehicle, heat pump, addition, new occupants, or efficiency work. Decide whether the goal is bill reduction, resilience, emissions reduction, more predictable costs, or a combination; batteries and panels answer different parts of those goals.

Resolve roof and site questions early

A satellite image is a starting point, not a structural or electrical assessment. Ask each bidder to state which site facts were verified in person and which remain assumptions.

• How many years of useful roof life remain, and what would removal and reinstallation cost if roofing is replaced later?
• Which roof planes have meaningful shade by season, and what objects create it?
• Can the structure and electrical service support the proposed work, subject to professional evaluation?
• What local setbacks, fire-access paths, homeowner-association rules, permits, and utility interconnection steps apply?
• Where would inverters, disconnects, conduit, and any battery equipment go?

Normalize every proposal

Do not compare only the projected monthly payment. A low payment can reflect a longer term, dealer fee, escalating lease payment, or an assumed incentive. Compare cash price first, then evaluate financing separately.

Test savings claims instead of accepting a single number

A savings estimate combines uncertain future variables: household use, system production, equipment degradation, utility rates, export credits, fixed charges, downtime, and financing. Ask for the year-by-year calculation or an exportable worksheet.

Run at least three cases: the seller’s case, a conservative case with lower production and slower utility-rate growth, and a household-change case. If the decision only works under the most optimistic assumptions, that is important information—not a reason to hide the assumptions.

Ask whether the model uses gross production or the amount expected to offset billed consumption after system losses. A proposal that shows accurate panel output can still overstate bill savings if it applies the wrong export credit, ignores fixed charges, or assumes your usage always coincides with solar production.

Before signing

Ask what happens if the final site visit produces a smaller design, a service-panel upgrade, roof work, trenching, or a utility requirement not shown in the original price. The contract should explain change orders, who may cancel, what deposit is refundable, and which milestone authorizes installation.

Review the company that will actually perform the work. The sales company, lender, designer, installer, monitoring provider, and warranty administrator may be different entities. Write each legal name and responsibility on one page, then check which company remains responsible if another stops operating.

1. 1

   Read the contract, financing agreement, warranty documents, production guarantee, cancellation terms, and any roof warranty as separate documents.

2. 2

   Confirm the installer’s license and insurance with the relevant state or local authority.

3. 3

   Write down who handles permits, utility approval, inspection corrections, equipment failure, roof leaks, monitoring access, and future removal.

4. 4

   Make sure verbal promises appear in the signed documents. If a promise is important enough to buy the system, it is important enough to write down.

Decide whether a battery belongs in the same project

A battery can shift solar energy to later hours and may provide backup for selected loads, but it changes price, equipment, space, permitting, maintenance, and replacement assumptions. Ask whether the proposed system can operate during an outage, which circuits it can support, for how long under a stated load, and whether solar can recharge it while the grid is down.

Compare the battery decision against the actual goal. For short outages, a smaller critical-load design may be enough. For medical equipment, well pumps, heating, or long outages, the load and weather assumptions need much more care. Do not equate the battery’s nameplate capacity with usable household runtime.