Getting a solar estimate should feel helpful, not confusing.
For many homeowners, the solar process starts with a simple question: would solar make sense for my home? But answering that question is not as simple as looking at your roof or guessing your monthly bill. A useful solar estimate needs to consider your home's electricity use, available roof space, solar production potential, local electricity rates, system cost assumptions, battery, and how solar energy lines up with the way your home actually uses power.
Blumi is designed to give homeowners a clear, preliminary solar and battery estimate before a final installer review. The estimate is not a final quote, engineering design, or guaranteed savings report. Instead, it is meant to provide a strong starting point: a practical, data-informed preview of what solar could look like for your home.
This page explains how Blumi creates that estimate, what information it uses, what assumptions go into the numbers, and why the results may change after a solar professional reviews your home in more detail.
What information Blumi starts with
Blumi begins with a few basic inputs from the homeowner. The most important pieces of information are:
- Your ZIP code
- Your home address
- Your average monthly electric bill
- Your selected solar panel count, if you adjust the estimate
- Your selected battery option, if you choose to explore battery storage
The two inputs that matter most for the estimate are your address and your average monthly electric bill. Your address helps Blumi understand your roof, your location, your state, and your general solar production potential. Your electric bill helps Blumi estimate how much electricity your household uses each year.
Together, those inputs help Blumi move from a generic solar estimate to something more specific to your home.
How Blumi estimates your electricity usage
Your electricity usage is one of the most important parts of the solar estimate. Many homeowners know roughly what they pay each month for electricity, but not everyone knows how many kilowatt-hours they use each year. Since solar system sizing is based on energy use, Blumi uses your average monthly electric bill to estimate your annual electricity consumption.
Estimated annual electric bill ÷ electricity rate = estimated annual kWh usage
$3,000 ÷ $0.15/kWh = 20,000 kWh estimated annual usage
How Blumi estimates the electricity rate
To estimate electricity usage and savings, Blumi needs an electricity rate. Depending on the installer's settings, Blumi may use either an installer-defined electricity rate or a state-level residential average electricity rate. If a manual rate is configured, that rate takes priority.
This rate is used to estimate how much electricity costs today and how much a homeowner might avoid paying by using solar energy in the future. For a preliminary estimate, this approach is useful because it creates a consistent baseline — but it is not the same as modeling every detail of a homeowner's actual utility tariff.
How Blumi uses roof and solar data
Blumi uses address-based solar and roof data to understand the home's solar potential. This can include information such as:
- Available roof area for solar panels
- Possible panel configurations
- Estimated solar production by configuration
- Roof segment orientation
- Panel placement data
- Satellite imagery and roof visualization data
This roof and solar data helps Blumi estimate how many panels may fit on the home and how much electricity those panels could produce in a typical year. Blumi uses this information as a starting point for the solar layout shown in the estimate. The roof image and panel overlay are meant to help homeowners visualize what solar could look like on their home.
The visualization is helpful for orientation and education, but it should not be treated as an engineering plan.
How Blumi estimates system size
Blumi estimates solar system size based on the number of panels selected and the assumed wattage of each panel.
8,000 W = 8.0 kW system size
The selected panel count may come from Blumi's recommended option, the homeowner's slider adjustment, or the closest available roof-supported panel configuration. This is important because not every panel count is physically or practically available for every roof. A homeowner may want a specific system size, but the roof data may only support certain panel layouts. Blumi uses available panel configurations to keep the estimate grounded in the home's actual roof potential.
How Blumi estimates solar production
System size tells you how large the solar system is. Solar production estimates how much electricity that system may generate. Blumi estimates annual solar production using available roof and production data, then converts that production into an AC-equivalent value for homeowner-facing calculations.
This distinction matters because solar panels produce DC electricity, while homes use AC electricity. In a real solar system, inverters and other system components convert DC power into AC power — and some energy is lost during that process. To account for this, Blumi applies a derate factor of 0.85 to estimate AC-equivalent solar production.
The AC-equivalent production is then compared against the home's estimated annual electricity usage. This gives homeowners a more practical view of how much of their electricity use solar could help cover.
How Blumi estimates solar offset
Solar offset is the percentage of your annual electricity use that could be covered by solar production.
Solar offset is helpful, but it can often be misunderstood. A 100% offset does not always mean your home will never use electricity from the grid. Solar panels produce the most energy during sunny daytime hours. Many homes use a lot of electricity in the morning, evening, or at night when solar production is lower or unavailable.
That means a home can have a high annual solar offset and still import some electricity from the grid at certain times. This is why Blumi looks beyond annual totals when possible — the timing of solar production matters.
Why Blumi models solar timing and home usage
A simple annual solar estimate can tell you how much energy a system might produce over a year. But it does not show when that energy is produced — and that timing matters.
Solar production usually peaks during the middle of the day. Home energy use often peaks in the morning or evening. Because of this mismatch, not every kilowatt-hour of solar production is used directly by the home at the moment it is generated.
Blumi's profile-based modeling compares estimated hourly solar production with estimated hourly home electricity usage. For each modeled hour, Blumi estimates direct solar used by the home, solar exported to the grid, and electricity imported from the grid.
→ home uses all available solar + imports the remainder from the grid If solar production > home usage:
→ home uses what it needs + exports the surplus to the grid
This allows Blumi to explain why solar can reduce your electric bill even if you still use the grid. It also helps estimate the value of a battery, since batteries are designed to store extra solar energy and use it later.
How Blumi estimates savings
Blumi estimates savings by comparing two scenarios: what your electricity costs could look like without solar, and what they could look like with solar.
Long-term net savings 25-year utility savings − estimated net system cost = estimated 25-year net savings
For long-term savings, Blumi projects this comparison across a 25-year horizon. Blumi also accounts for solar production degradation over time — solar panels are expected to produce slightly less electricity each year as they age, so the model includes a small annual production degradation assumption of 0.5% per year.
Utility savings are not the same as net savings. To estimate net savings, Blumi subtracts the estimated solar system cost from the modeled utility savings. This helps homeowners understand the difference between avoiding utility bills and recovering the cost of the system itself.
How Blumi estimates system cost
Blumi estimates solar system cost using an installed cost-per-watt assumption.
Because preliminary costs are not final quotes, Blumi presents system cost as a range rather than a single exact number. Solar pricing can change based on equipment, roof difficulty, electrical upgrades, permitting requirements, incentives, and site-specific conditions. The cost range gives homeowners a more honest starting point to assess whether solar is right for their home.
How Blumi thinks about recommended system size
Blumi does not simply recommend the largest system that can fit on the roof. A larger system can produce more electricity, but bigger is not always better. In some cases, adding more panels may increase the upfront cost without adding enough additional financial value — especially when exported solar receives a lower credit than electricity purchased from the grid. In other cases, utility companies may have restrictions on how large a solar system can be in order to be eligible for net metering, typically at or around 100% solar offset.
Blumi's recommendation logic generally looks for a system that balances:
- Long-term savings
- Annual solar offset
- Upfront system cost
- Roof-supported panel configurations
- Avoiding unnecessary oversizing
In many cases, Blumi prefers systems that fall within a practical offset range rather than automatically pushing toward the maximum roof size. If the roof cannot support enough solar to reach that range, Blumi may recommend the strongest available option.
How Blumi estimates export credits and net metering
When solar panels produce more electricity than your home is using at that moment, the extra electricity may be sent to the grid. Depending on your utility and local solar policy, that exported electricity may receive a credit.
Some areas have more favorable net metering rules. Others credit exported solar at a lower rate. Some utility programs are more complex and may change over time. Blumi uses an export credit assumption configured for the estimate, and this assumption matters because it affects the value of excess solar production.
If exported solar is credited at the full retail rate, a larger system may be more financially attractive. If exported solar is credited at a lower rate, it may be better to size the system more carefully around the home's actual electricity use. Because utility rules vary widely, export credit assumptions should be confirmed during installer review.
How Blumi estimates battery value
Batteries can add value in several ways, but they are not always purchased for the same reason. Some homeowners care most about having backup power. Others care about using more of their own solar energy. Some want protection from outages, while others want more control over grid dependence.
Blumi estimates battery impact by modeling how a selected battery could interact with the home's solar and load profile. The battery model generally follows this pattern:
This allows Blumi to estimate how a battery may affect solar self-consumption, grid imports, exported solar, and backup potential. The financial value of a battery depends heavily on local rates and export credit rules. If exported solar receives a low credit, storing extra solar for later use can be more valuable. If exported solar receives a strong credit, the financial return from a battery may be more limited.
How Blumi estimates backup duration
A battery may not always produce strong financial payback, but it may still be valuable to a homeowner who wants backup power during outages. Blumi estimates backup duration by modeling an outage scenario starting from a full battery, using a simplified essential-load profile rather than assuming the home continues using electricity exactly the same way it would during normal grid-connected operation.
This is important because during an outage, most homeowners do not power every appliance in the home. Instead, they may only back up essential circuits — such as refrigeration, lighting, internet, outlets, medical devices, or selected heating and cooling equipment. Blumi's backup estimate may consider scenarios such as:
- Battery-only backup
- Backup with limited solar recharge
- Backup with stronger solar recharge
- Sunny conditions where solar may help sustain backup longer
Actual backup duration can vary significantly depending on which circuits are backed up, battery size and reserve settings, weather conditions, solar production during the outage, appliance usage, HVAC usage, installer design, and household behavior during the outage.
How Blumi estimates environmental impact
Blumi also estimates the environmental impact of solar production. The model looks at how much useful solar energy the system may produce and applies emissions assumptions based on regional grid electricity — including solar energy used directly by the home, solar energy delivered through the battery, and exported solar that may help displace grid electricity elsewhere.
Blumi then converts the avoided emissions into numbers that are easier to understand, such as metric tons of CO₂e avoided, passenger cars taken off the road for one year, gallons of gasoline avoided, and tree seedlings grown for 10 years. These figures are estimates intended to make the environmental impact easier to understand, not to provide a lifecycle carbon accounting report.
Why the estimate may change after installer review
Blumi's estimate is designed to be useful before the first sales conversation, but it is not the final word. A solar installer may adjust the estimate after reviewing:
- Roof condition and age
- Shading and obstructions
- Fire setbacks and local building codes
- Electrical panel capacity
- Utility rules and interconnection requirements
- Equipment selection and battery design
- Financing structure and incentive eligibility
- Final system layout and homeowner goals
Some changes may be small. Others may materially affect system size, cost, savings, battery recommendations, or installation feasibility. A preliminary estimate is intended to help homeowners understand the opportunity. A final quote should come from a qualified installer after reviewing the home in more detail.
FAQ
Common questions
No. A Blumi estimate is a preliminary solar and battery estimate. It gives homeowners a helpful starting point, but final system size, equipment, pricing, savings, and battery recommendations may change after installer review.
Blumi uses your average monthly bill to estimate your annual electricity usage. Since solar system sizing depends on how much electricity your home uses, this helps create a more personalized estimate.
Electric bills can include fixed charges, taxes, delivery fees, minimum charges, seasonal changes, and different rate structures. Blumi uses your bill as a practical proxy, but a detailed utility bill review can improve accuracy.
No. Blumi may show a preliminary roof visualization and panel overlay, but this is not a final engineering design. Final panel placement depends on installer review, roof conditions, code requirements, shading, and equipment selection.
Solar offset is based on annual production compared with annual usage. But solar production and home usage happen at different times of day. A home may export extra solar during the day and still import electricity at night.
Blumi's current methodology is cautious with incentives. Incentives may be noted, but they are not directly included in the savings calculations. Eligibility should be confirmed with the installer or a tax professional.
Blumi's current homeowner estimate is primarily based on a cash-purchase model. It does not fully model loans, leases, interest rates, or dealer fees.
No. Battery backup estimates are directional. Actual backup duration depends on the battery system, backed-up circuits, weather, solar recharge, reserve settings, appliance use, and installer design.
Environmental impact helps homeowners understand the potential emissions benefit of solar production. These figures are based on emissions assumptions and equivalency conversions, so they should be treated as estimates rather than exact carbon accounting.