curl --request GET \
  --url https://api.voltview.co.uk/v1/sites/annualSpendAndSavings \
  --header 'Authorization: Bearer <token>'

[
  {
    "siteId": "<string>",
    "period": "<string>",
    "spend": 123,
    "savings": 123,
    "comparisonPeriod": "<string>",
    "previousSpend": 123,
    "spendChange": 123
  }
]