The Sunollo Savings Guarantee: Exactly How We Calculate What You Save — Every Month, Every Year

Every month, Sunollo collects your subscription payment. In return, we make a promise: the solar system on your roof will put more money back into your pocket than you pay us. That promise is the Sunollo Savings Guarantee.

This article is our full, transparent account of how that guarantee works. Not a marketing summary — a complete explanation. You will find the exact formula we use, a month-by-month worked example for a real Singapore home, a plain-language explanation of every condition that applies, and a clear description of what happens at your annual assessment. By the end, you will be able to verify your own savings independently, any time you want.

We think that is how a guarantee should work.

The Guarantee in One Sentence

Over any full 12-month period from your commissioning anniversary, the monetary value of electricity your Sunollo system saves you — calculated using SP Group's own published rates — will exceed the total subscription fees you paid us for that period.

If it does not, Sunollo credits you the difference. You do not need to ask. We calculate it, we tell you, and we apply the credit to your next invoice.

Part 1: How Solar Saves You Money — The Two Streams

Stream 1: Self-Consumption — Displacing What You Would Have Bought

When your solar panels are generating and your home is consuming electricity at the same time — running the air-conditioning, the washing machine, the refrigerator, the lights — your home draws from your roof first, before touching the grid. Every kilowatt-hour you consume directly from solar is one kilowatt-hour you did not have to buy from SP Group.

Think of it as a direct displacement of your most expensive electricity. The value of each self-consumed kilowatt-hour equals the full SP retail tariff you avoided paying — approximately SGD 0.29–0.31/kWh depending on the current quarter.

Stream 2: Export Earnings — Getting Paid for What Your Home Cannot Use

During peak solar hours — typically 9 AM to 3 PM — your panels often produce more electricity than your household can absorb in real time. That surplus flows through your smart meter and into the national grid, and SP Group credits you for it through the Net Energy Rebate (NER) scheme.

The NER rate is based on the Uniform Singapore Energy Price (USEP), the wholesale electricity market price in Singapore. As an estimate, the NER rate typically works out to approximately 75–80% of the full SP retail tariff — meaningfully higher than most customers expect. This is because the USEP reflects the energy cost component of electricity, which is the largest single component of the retail tariff.

Important note on NER rate: The 75–80% figure is an estimate based on observed USEP-to-retail relationships in Singapore's electricity market. The actual rate varies each quarter and is published by SP Group. Your Annual Savings Statement will always use the exact published NER rate for each billing period, not an estimate.

Part 2: The Formula

Sunollo calculates your savings using a single, consistent formula. Every input comes from a publicly verifiable source.

Monthly Gross Savings = (kWh self-consumed × SP purchase rate) + (kWh exported × SP NER export rate)

Monthly Net Savings = Monthly Gross Savings − Monthly Subscription Fee

Annual Net Savings (the Guarantee Metric) = Sum of all 12 Monthly Net Savings = (Total Annual Gross Savings) − (Total Subscription Paid for the Year)

The guarantee condition: Annual Net Savings > SGD 0.

SP purchase rate source: SP Group quarterly tariff, published at spgroup.com.sg and shown on your bill. NER rate source: SP Group quarterly NER rate (USEP-based), ~75–80% of purchase rate as estimate; exact rate shown on SP bill. Both rates are set by SP Group, not by Sunollo. Everything is independently verifiable.

Part 3: A Real Year in Numbers

Here is a complete 12-month example for a typical Sunollo customer — a family of four in a landed property with a 10 kWp system and a monthly subscription of SGD 100. SP rates are illustrative based on recent published figures. NER rate is set at approximately 75% of the SP purchase rate for each quarter.

Annual Net Saving: SGD 836.88. The Savings Guarantee is met with a strong margin. The system generated over SGD 836 above its own subscription cost — real money that would otherwise have gone to SP Group.

Note: Every single month is positive. Even December — Singapore's lowest-generation month — delivers a net saving of SGD 43.79. With NER at approximately 75% of retail, the economics remain strong even in weaker solar months.

Part 4: Why Your Monthly Savings Will Vary

Monthly variation is completely normal. Four independent variables drive it:

1. Singapore's solar seasons. The Northeast Monsoon (November–January) and Southwest Monsoon (June–August) bring more cloud cover and lower irradiance. The inter-monsoon periods (February–May, September–October) are generally the sunniest. Generation in peak months can be 25–40% higher than in the lowest months. Compare the same month year-on-year, not month to month.

2. How you use electricity during the day. Self-consumed solar saves ~SGD 0.30/kWh. Exported solar earns approximately 75–80% of that, so ~SGD 0.22–0.24/kWh. Both are excellent — but the more you run appliances during daytime solar hours, the higher your monthly saving, because you capture the full retail rate rather than the NER rate.

3. SP Group's quarterly tariff changes. When the tariff rises, the value of your self-consumed solar rises automatically — without any change to your system. This is one reason rising electricity prices are good news for solar subscribers.

4. The USEP-linked NER rate. Changes quarterly alongside energy market movements. Tracked in your Annual Savings Statement at the exact published rate for each period.

Because these four variables move independently, it is entirely normal for a month to feel weaker than expected while the full annual picture remains strong. This is exactly why the guarantee is annual, not monthly.

Part 5: The Annual Assessment — How It Works

The guarantee is assessed on the 12-month anniversary of your solar commissioning date.

Step 1 — Data Collection: Sunollo retrieves 12 months of generation data from your monitoring platform and cross-references with your SP billing data to confirm export volumes and NER credits received.

Step 2 — Rate Application: The exact SP retail tariff and NER rate published by SP Group for each quarter are applied. Each month gets the rate in force at the time — no averages, no retroactive adjustments.

Step 3 — Exclusion Adjustments: Any qualifying downtime periods (maintenance, repair, grid outage) are documented and the annual production target is adjusted proportionally.

Step 4 — Annual Savings Statement: Sunollo sends you a detailed statement showing month-by-month generation and savings, SP rates applied, total subscription paid, exclusion adjustments, and the final net savings figure with a clear Guarantee Met / Shortfall determination.

Step 5 — Resolution: If guarantee is met: statement serves as your annual record. If shortfall exists: Sunollo calculates the amount and applies a credit to your next subscription invoice automatically. If you disagree with any figure: you have 30 days to query; Sunollo responds within 14 working days.

Part 6: The Three Conditions — When Guarantee Parameters Change

Condition 1: Material Change in Your Electricity Usage Pattern

Your subscription was priced based on your historical electricity consumption. A change is material if your annual total electricity consumption differs from the evaluation baseline by more than 25% — a significant threshold designed to absorb normal life variation.

Triggers: Family members permanently relocating; extended absence abroad (more than 2 months combined per year); removal of major electricity-consuming appliances that were part of the original evaluation; property becoming partially or fully vacant.

Does NOT trigger: Normal seasonal variation; occasional holidays; minor lifestyle changes; adding new appliances (which actually improves self-consumption).

What to do: Notify Sunollo at [email protected] if circumstances change significantly. We will review your actual consumption against the baseline and work with you on a fair adjustment — which may include a revised subscription, a new production baseline, or both.

Condition 2: Physical Changes That Reduce Solar Access

Your system was modelled on your roof's solar access at the time of the site survey. If that access changes materially, the original projection no longer applies.

Triggers: A new adjacent building or structure shading your panels during peak generation hours; significant tree growth not accounted for in the original survey; modifications to your roof or the solar system made without Sunollo's written approval.

Special note on new neighbouring structures: If a developer or neighbour constructs a building that materially reduces your generation, Sunollo will document the before-and-after performance impact in your Annual Savings Statement — providing evidence you can use to support a compensation claim against the relevant party. We will also reassess your production baseline and review whether system adjustments can restore your savings position.

What to do: Notify Sunollo as soon as you become aware of any new potential shading source. Establishing a before-and-after baseline as early as possible protects your position.

Condition 3: Documented System Downtime

Legitimate offline periods are excluded from the guarantee calculation. This is fair to both parties.

Excluded downtime includes: Scheduled preventive maintenance (Sunollo notifies you at least 5 working days in advance); fault repair periods from the date you notify Sunollo to system restoration — note: the exclusion clock starts when Sunollo is notified, not when the fault began, so report faults promptly; and SP Group grid outages (anti-islanding shutdown, outside anyone's control).

Every excluded period appears in your Annual Savings Statement with dates, duration, and reason.

Part 7: Maximising Your Savings

The guarantee protects your downside. These habits push your savings higher.

The core insight: Self-consumed solar saves ~SGD 0.30/kWh. Exported solar earns ~SGD 0.22–0.24/kWh. Shifting consumption to daytime solar hours is the highest-leverage action available.

Run laundry and dishwashing 9 AM–3 PM. Set timers the night before. A single daily wash load shifted to solar hours saves SGD 100–200 per year vs running at night.

Pre-cool with aircon during peak solar. Run aircon at a comfortable temperature until 5 PM using solar power, then switch to fan. A pre-cooled room with a ceiling fan stays comfortable for 2–3 hours. Running two rooms of aircon for 3 hours on solar vs grid saves SGD 540–900 per year from this one habit alone.

Set your water heater to reheat 10 AM–1 PM rather than overnight.

Charge your EV between 10 AM and 2 PM. An EV averaging 30 kWh/week shifted to solar hours saves approximately SGD 468/year vs overnight grid charging.

Clean panels twice a year (April and October). Soiling reduces output 5–15% in Singapore's tropical climate. The cost of a professional clean is recovered in 2–4 weeks of restored generation.

Part 8: Your Rights as a Sunollo Customer

The right to verify: Every input to your savings calculation is independently verifiable. Your monitoring app, your SP bill, and SP Group's published tariffs are all you need to replicate the calculation yourself.

The right to a mid-year summary: At any point, email [email protected] to request a mid-year savings summary. We produce it within 5 working days.

The right to query your annual statement: You have 30 days from the statement date to raise a formal query. We acknowledge within 2 working days and provide a full response within 14 working days. Errors found in our favour are corrected and credited immediately.

The right to access your baseline data: Your evaluation consumption data and roof assessment are retained on file. You can request a copy at any time — it is your data.

Frequently Asked Questions

Q: My SP bill NER credit seems lower than 75–80% of retail. Why?
The 75–80% figure is an estimate of the typical USEP-to-retail relationship. In some quarters it may be lower (around 65–70%) or higher (around 85%) depending on global energy markets. Your Annual Savings Statement uses the exact published NER rate for each quarter, not the estimate. If a particular quarter's rate was lower than average, it is reflected accurately.

Q: What if the SP tariff goes up significantly?
Good news for you. Every increase in the SP retail tariff automatically increases the value of your self-consumed solar energy, using the same formula. Your subscription stays fixed while the value of your solar output rises. Rising electricity prices benefit solar subscribers.

Q: I went on holiday for three weeks. Does that affect my guarantee?
Almost certainly not. A three-week holiday shifts one month's net saving from, say, SGD 70 to SGD 55. Over a full year, this is well within normal variation and far below the 25% materiality threshold for usage changes.

Q: My neighbour is building a new floor that will shade my panels from 11 AM. What should I do?
Notify Sunollo immediately — ideally before construction begins. We will document your current performance as a baseline, assess the projected generation impact, adjust your guarantee parameters accordingly, and provide documentation to support any compensation claim against the developer.

Q: Can I check my savings before my anniversary?
Yes. Your monitoring app and SP bill have everything you need. Email [email protected] if you would like a formatted mid-year summary from Sunollo — we prepare it within 5 working days.

Q: Does the guarantee apply every year or just the first?
Every complete 12-month period of your subscription. Year 1 assessed at month 12, year 2 at month 24, and so on for the full subscription term.

Q: I have a battery. Does that change the calculation?
A battery changes the timing of self-consumption but not the formula. Energy stored during the day and discharged in the evening counts as self-consumed solar. Batteries typically increase your self-consumption ratio by 15–30%, which increases your gross savings under the same formula.

A Closing Note on Why Transparency Matters to Us

Solar subscriptions are long-term commitments. You are trusting Sunollo with a piece of your home's infrastructure for years. We think that kind of trust should be earned through how we behave, not just how we market ourselves.

Sunollo's Savings Guarantee is built on publicly verifiable numbers because we believe a guarantee is only meaningful if the customer can check it themselves. We use SP Group's own published rates. We assess annually because individual months are noisy — but 12 months tells the real story. We document every exclusion condition explicitly and transparently, because a guarantee with hidden escape clauses is not a real guarantee.

If your system is not saving you more than it costs, we owe you money. That is the deal. We are confident the deal works — for you and for us — because we designed the system, sized it for your home, and stand behind its performance.

If you have questions about your savings, your monitoring data, or anything in this article, email us at [email protected]. We respond to every email.