How to Check Your Solar Savings on Your Smart Meter

Step-by-step method for calculating exactly how much your plug-in solar is saving you, using your smart meter data and supplier app.

Why You Should Track Savings Properly

"Is my plug-in solar actually saving me money?" is the question everyone asks after the first month. Your smart meter gives you the raw data to answer it precisely — no estimation needed.

The method below works for any plug-in solar system from 400W to 800W. You'll need access to your supplier app and about 10 minutes.

Step 1: Get Your Pre-Solar Baseline

Before you can measure savings, you need to know what you were using before solar. Two options:

If you had a smart meter before installing solar — check your supplier app for average daily consumption in the same month last year, or the month before installation. Write this down as your baseline (e.g., 10.5 kWh/day average in May).

If you got your smart meter at the same time as solar — use a cloudy week's data as a rough baseline. On heavily overcast days your panels produce very little, so your import approximates pre-solar usage. Not perfect, but workable.

Step 2: Calculate Daily Import Reduction

Open your supplier app and look at your daily import figures for a representative week (avoid days with unusual usage — house parties, holidays, etc.).

Average daily import with solar = sum of daily imports ÷ number of days

Daily import reduction = baseline daily import − current daily import with solar

For a south-facing 800W system in May, expect a daily import reduction of 2.5–4 kWh on average, accounting for cloudy days.

Step 3: Convert to Money

Daily saving = daily import reduction × your unit rate

If your unit rate is 24.5p/kWh and your daily import reduction is 3 kWh:

3 × £0.245 = £0.74/day

Monthly saving = daily saving × 30

£0.74 × 30 = £22.10/month

This is your import saving only. If you're also receiving SEG export payments, add those separately — your supplier app or SEG statement will show the amount.

Step 4: Annualise (Accounting for Seasons)

Solar output varies dramatically by season. A system that saves you £22/month in May might save £8/month in December and £28/month in July. Use our savings calculator for a location-specific annual estimate, or track monthly and sum at year-end.

As a rough rule for a UK 800W system: annual savings are typically £200–350 depending on location, orientation, and how well you optimise self-consumption.

Step 5: Calculate Your Payback Period

Payback period = total system cost ÷ annual saving

If your 800W kit cost £799 and your annual saving is £280:

£799 ÷ £280 = 2.85 years

After payback, it's pure profit for the remaining 20+ years of panel life.

Common Mistakes

Comparing different months — don't compare January (low solar) to July (high solar) consumption and call the difference your saving. Compare like-for-like: same month, before and after solar.

Forgetting standing charges — your daily standing charge is the same with or without solar. Don't include it in savings calculations — only unit rate savings count.

Ignoring tariff changes — if your unit rate changed between your baseline period and now, adjust accordingly. Use the current rate for both calculations.

Double-counting battery charging — if you have a battery, energy stored and used later is still a saving (it's self-consumption). But don't count it as both saved import and avoided export.

Automating the Tracking

For ongoing tracking without manual maths:

Octopus Energy users can access their half-hourly data via the app, which shows import reduction clearly
Loop Energy (free app) connects to your smart meter via the DCC and provides solar-specific analytics
The EcoFlow app shows generation and self-consumption directly if you have a STREAM system