How Much Is Your Solar System Really Saving You?

By Olivier Beauchemin · Updated May 2026

Your installer told you solar would save you $1,500 a year. Maybe $2,000. But now that the system is on your roof, how do you know if that's actually happening? Your electric bill isn't zero, your monitoring app shows kilowatt-hours but not dollars, and nobody is doing the math for you.

Calculating your actual solar savings isn't complicated, but it requires understanding how the pieces fit together. This guide walks through the framework, with real numbers for the Northeast where electricity rates make the math particularly consequential.

The Basic Savings Equation

Your solar savings come from two sources:

Let's break that down:

• Self-consumed solar is the electricity your panels produce that you use directly in your home. Every kWh you self-consume is a kWh you didn't buy from the grid, so you save the full import rate.
• Exported solar is the surplus electricity your panels send to the grid. You receive a credit for each exported kWh. The value of that credit depends on your net metering arrangement.

Net Savings vs. Gross Savings

Your net savings also account for costs that solar doesn't eliminate:

Even with solar, you'll still pay fixed utility charges (customer charges, distribution fees, minimum bills). And if you financed your system, your loan payment offsets some or all of your utility savings in the near term.

Worked Example: 10 kW System in New England

Let's walk through a realistic example for a homeowner in New England.

System and Rate Assumptions

• System size: 10 kW
• Annual production: 12,000 kWh (based on ~1,200 kWh/kW for NE per NREL PVWatts)
• Self-consumption ratio: 35% (illustrative figure for a home without battery storage)
• Electricity import rate: $0.28/kWh
• Net metering export credit: $0.28/kWh (full retail, common in NE states)
• Monthly fixed charges: $12/month ($144/year)

Annual Savings Calculation

• Self-consumed solar: 12,000 x 35% = 4,200 kWh x $0.28 = $1,176
• Exported solar: 12,000 x 65% = 7,800 kWh x $0.28 = $2,184
• Gross savings: $1,176 + $2,184 = $3,360/year
• Minus fixed charges still owed: $3,360 - $144 = $3,216 net annual savings

This is a simplified illustration. Actual savings depend on your specific rate structure, consumption pattern, and net metering terms.

What Happens When Export Credits Are Less Than Retail?

If your state or utility has moved to reduced-rate net metering (as some are doing), the math changes significantly. Using the same system but with export credits at $0.14/kWh (50% of retail):

• Self-consumed: 4,200 kWh x $0.28 = $1,176 (unchanged)
• Exported: 7,800 kWh x $0.14 = $1,092 (was $2,184)
• Gross savings: $1,176 + $1,092 = $2,268/year
• Net savings: $2,268 - $144 = $2,124/year

That's $1,092 less per year — a 34% reduction in savings — purely from the change in export compensation. This is why understanding your specific net metering terms is critical, and why maximizing self-consumption becomes more important when export credits are below retail rate.

The Self-Consumption Lever

When your export credit rate is less than your import rate, every kWh you shift from export to self-consumption is worth more. Strategies to increase self-consumption include:

• Shift heavy loads to solar hours (10 AM - 3 PM): Run your dishwasher, laundry, and EV charging during peak solar production. Some smart home systems can automate this.
• Battery storage: A home battery stores excess solar production for evening use, eliminating the export-import mismatch. Batteries add cost but can dramatically improve savings in reduced-NEM environments.
• Heat pump water heaters: Using midday solar to heat water is one of the most cost-effective forms of solar self-consumption — the tank acts as a thermal battery.

A system with 50% self-consumption instead of 35% and the reduced NEM scenario above:

• Self-consumed: 6,000 kWh x $0.28 = $1,680
• Exported: 6,000 kWh x $0.14 = $840
• Gross savings: $1,680 + $840 = $2,520/year

That's $252/year more than the 35% self-consumption case — just from shifting when you use electricity. Over 25 years, that's over $6,000 in additional value.

Costs That Solar Doesn't Eliminate

Several utility charges persist even with a solar system that produces 100% of your annual consumption:

Fixed Customer Charges

Every utility charges a monthly customer charge ($8-$20/month in New England, varying by utility) simply for being connected to the grid. Solar doesn't reduce this.

Demand Charges

Some rate plans (particularly in commercial and certain residential territories) include demand charges based on your peak power draw during the billing period. A brief spike in consumption — starting an air conditioner, running multiple appliances simultaneously — can trigger a demand charge that solar doesn't offset because the spike may occur when the sun isn't shining.

Minimum Bill Requirements

Some utilities impose a minimum monthly bill (typically $10-$25 in New England) regardless of solar production. Even if your net usage is zero or negative, you still owe the minimum.

Rate Riders and Surcharges

Many utilities add various surcharges to every bill — energy efficiency charges, renewable energy charges, transmission upgrades — that apply regardless of your solar production. These can add $5-$15/month.

Why Your Installer's Savings Estimate May Be Wrong

Solar installers project savings based on assumptions made at the time of sale. Those assumptions can diverge from reality in several ways:

• Rate assumptions: The installer assumed a certain electricity rate and rate escalation. If rates changed differently than projected, your actual savings differ from the estimate.
• Production assumptions: The installer's production estimate uses modeled weather data, not actual weather. A system that was projected to produce 12,500 kWh/year based on a 30-year weather average may produce 11,500 kWh in a cloudier-than-average year.
• Consumption assumptions: Your system was sized for your historical consumption. If you've added an EV, a heat pump, or other loads, your system may no longer cover your usage. See our guide on why your bill might still be high.
• Net metering assumptions: If your state or utility changed net metering rules after installation, the installer's savings projection based on the old rules no longer applies.
• System underperformance: If your system isn't producing what it should — due to equipment failure, shading, or excessive degradation — your actual savings are lower. See our guide on identifying underperformance.

How to Calculate Your Actual Savings

To determine your real savings, gather these numbers:

1. Your pre-solar annual electricity cost — total utility bills for the 12 months before your system was activated
2. Your post-solar annual electricity cost — total utility bills for the 12 months after activation
3. Your solar production — total kWh produced (from your monitoring system)
4. Any solar loan payments — total annual payments on your solar financing

Simple savings estimate:

This simple comparison has a flaw: it doesn't account for changes in your consumption or changes in electricity rates between the two periods. A more accurate calculation uses your monitoring data and current rates:

If your monitoring system doesn't separately track self-consumption and exports, you can estimate: your total solar production minus your grid import equals your approximate self-consumption, and the rest was exported.

How OwlWatt Quantifies Your Savings

OwlWatt connects your production monitoring and utility billing data to give you a complete savings picture:

• Actual savings calculation based on your real production, consumption, and rate structure — not estimates
• Savings gap analysis showing the difference between your actual savings and what you should be saving if your system were performing to spec
• Rate-aware alerts that translate production shortfalls into the dollar amounts they're costing you at your specific electricity rate
• Bill verification that ensures your utility is correctly crediting your solar exports and applying the right rate plan

Your solar system is a financial asset. Like any investment, knowing its actual return — not just its projected return — is essential to managing it effectively. The difference between projected and actual savings is also the most reliable signal that something needs attention: a degrading panel, a misconfigured net metering rate, or a utility billing error that has been quietly costing you money for months.