diff --git a/DESCRIPTION b/DESCRIPTION
index 462c7ed..a6f6ee4 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -1,7 +1,7 @@
 Package: mrprom
 Type: Package
 Title: Functions for generating input data for OPEN-PROM
-Version: 1.27.4
+Version: 1.27.5
 Author: Anastasis Giannousakis, Fotis Sioutas, Giannis Tolios, Michael Madianos, Alexandros Tsimpoukis, Songmin Yu
 Maintainer: Fotis Sioutas <fotis.sioutas@wsp.com>
 Description: mrprom can be run standalone or (preferably) in
diff --git a/R/fullOPEN-PROM.R b/R/fullOPEN-PROM.R
index a5ea316..7c1e28f 100644
--- a/R/fullOPEN-PROM.R
+++ b/R/fullOPEN-PROM.R
@@ -209,8 +209,11 @@ fullOPEN_PROM <- function() {
   x <- calcOutput("IFuelPrice", aggregate = FALSE)
   # POP is weights for aggregation, perform aggregation
   x <- toolAggregate(x, weight = POP, rel = map, from = "ISO3.Code", to = "Region.Code")
+  # Replace existing BMSWAS keys with annual regional MAgPIE prices.
+  # The source is kUSD2015/toe; toolReplaceBMSWASPrice converts it back to
+  # IFuelPrice's USD2015/toe before this file is written.
+  xq <- toolReplaceBMSWASPrice(x)
   # write input data file that GAMS can read
-  xq <- as.quitte(x)
   xq <- xq[!is.na(xq[["value"]]), ] %>%
     select(c("period", "value", "region", "variable", "new")) %>% # nolint
     pivot_wider(names_from = "period") # nolint
diff --git a/R/readMAgPIE_BMSWAS_Price.R b/R/readMAgPIE_BMSWAS_Price.R
new file mode 100644
index 0000000..f93c51b
--- /dev/null
+++ b/R/readMAgPIE_BMSWAS_Price.R
@@ -0,0 +1,82 @@
+#' readMAgPIE_BMSWAS_Price
+#'
+#' Read annual regional bioenergy prices prepared from a MAgPIE report for use
+#' as OPEN-PROM's historical BMSWAS fuel price. The source file is already in
+#' OPEN-PROM region and subsector space and uses kUSD2015/toe.
+#'
+#' @return The MAgPIE BMSWAS price data as a magpie object.
+#'
+#' @author Songmin Yu
+#'
+#' @examples
+#' \dontrun{
+#' x <- readSource("MAgPIE_BMSWAS_Price")
+#' }
+#'
+#' @importFrom quitte as.quitte
+#' @importFrom magclass as.magpie
+#' @importFrom tidyr pivot_longer
+#' @importFrom utils read.csv
+#'
+readMAgPIE_BMSWAS_Price <- function() {
+  sourceFile <- "iPrices_magpie.csv"
+  x <- read.csv(sourceFile, check.names = FALSE)
+
+  if (ncol(x) < 3) {
+    stop(sourceFile, " must contain region, SBS, and annual price columns")
+  }
+
+  names(x)[1:2] <- c("region", "variable")
+  yearColumns <- names(x)[-(1:2)]
+  expectedYears <- as.character(2010:2100)
+
+  if (!identical(yearColumns, expectedYears)) {
+    stop(sourceFile, " must contain annual columns 2010 through 2100 in order")
+  }
+  if (nrow(x) != 39 * 34 || length(unique(x$region)) != 39 ||
+      length(unique(x$variable)) != 34) {
+    stop(sourceFile, " must contain exactly 39 regions x 34 SBS rows")
+  }
+  if (anyDuplicated(x[c("region", "variable")])) {
+    stop(sourceFile, " contains duplicate region-SBS keys")
+  }
+
+  priceMatrix <- as.matrix(x[yearColumns])
+  storage.mode(priceMatrix) <- "numeric"
+  if (anyNA(priceMatrix) || any(!is.finite(priceMatrix)) || any(priceMatrix < 0)) {
+    stop(sourceFile, " contains missing, non-finite, or negative prices")
+  }
+
+  regionVariation <- vapply(
+    split(seq_len(nrow(x)), x$region),
+    function(rows) max(apply(priceMatrix[rows, , drop = FALSE], 2, function(v) max(v) - min(v))),
+    numeric(1)
+  )
+  if (any(regionVariation > 1e-12)) {
+    stop(sourceFile, " contains subsector-varying prices within a region")
+  }
+
+  x <- tidyr::pivot_longer(
+    x,
+    cols = all_of(yearColumns),
+    names_to = "period",
+    values_to = "value"
+  )
+  x$period <- as.integer(x$period)
+  x$unit <- "kUSD2015/toe"
+  x <- as.quitte(x) %>% as.magpie()
+
+  list(
+    x = x,
+    weight = NULL,
+    description = c(
+      category = "Costs",
+      type = "MAgPIE bioenergy price for OPEN-PROM BMSWAS",
+      filename = sourceFile,
+      `Indicative size (MB)` = 1.2,
+      dimensions = "3D",
+      unit = "kUSD2015/toe",
+      Confidential = "project"
+    )
+  )
+}
diff --git a/R/toolReplaceBMSWASPrice.R b/R/toolReplaceBMSWASPrice.R
new file mode 100644
index 0000000..e6d5af4
--- /dev/null
+++ b/R/toolReplaceBMSWASPrice.R
@@ -0,0 +1,57 @@
+#' Replace aggregated BMSWAS prices with MAgPIE prices
+#'
+#' Replaces only existing BMSWAS region-SBS-year values. The MAgPIE source is
+#' expressed in kUSD2015/toe, while IFuelPrice is written in USD2015/toe.
+#'
+#' @param x Regionally aggregated IFuelPrice magpie object.
+#'
+#' @return IFuelPrice as a quitte data frame with BMSWAS values replaced.
+#'
+#' @importFrom madrat readSource
+#' @importFrom quitte as.quitte
+#'
+toolReplaceBMSWASPrice <- function(x) {
+  fuelPrices <- as.quitte(x)
+  requiredColumns <- c("region", "variable", "new", "period", "value")
+  if (!all(requiredColumns %in% names(fuelPrices))) {
+    stop("Aggregated IFuelPrice is missing required dimensions")
+  }
+
+  magpiePrices <- as.quitte(readSource("MAgPIE_BMSWAS_Price"))
+  if (!all(c("region", "variable", "period", "unit", "value") %in% names(magpiePrices))) {
+    stop("MAgPIE BMSWAS price source is missing required dimensions")
+  }
+  if (!identical(unique(as.character(magpiePrices$unit)), "kUSD2015/toe")) {
+    stop("MAgPIE BMSWAS prices must use kUSD2015/toe")
+  }
+
+  magpieKey <- paste(magpiePrices$region, magpiePrices$variable, magpiePrices$period, sep = "\r")
+  if (anyDuplicated(magpieKey)) {
+    stop("MAgPIE BMSWAS price source contains duplicate region-SBS-year keys")
+  }
+
+  replaceRows <- fuelPrices$new == "BMSWAS"
+  if (!any(replaceRows)) {
+    stop("Aggregated IFuelPrice contains no BMSWAS values to replace")
+  }
+  if (!identical(unique(as.character(fuelPrices$unit[replaceRows])), "USD2015/toe")) {
+    stop("IFuelPrice BMSWAS values must use USD2015/toe before replacement")
+  }
+  targetKey <- paste(
+    fuelPrices$region[replaceRows],
+    fuelPrices$variable[replaceRows],
+    fuelPrices$period[replaceRows],
+    sep = "\r"
+  )
+  sourceRows <- match(targetKey, magpieKey)
+  if (anyNA(sourceRows)) {
+    missingKeys <- unique(targetKey[is.na(sourceRows)])
+    stop(
+      "MAgPIE BMSWAS prices do not cover all existing IFuelPrice keys; first missing key: ",
+      missingKeys[[1]]
+    )
+  }
+
+  fuelPrices$value[replaceRows] <- magpiePrices$value[sourceRows] * 1000
+  fuelPrices
+}
diff --git a/man/readMAgPIE_BMSWAS_Price.Rd b/man/readMAgPIE_BMSWAS_Price.Rd
new file mode 100644
index 0000000..50c13f8
--- /dev/null
+++ b/man/readMAgPIE_BMSWAS_Price.Rd
@@ -0,0 +1,25 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/readMAgPIE_BMSWAS_Price.R
+\name{readMAgPIE_BMSWAS_Price}
+\alias{readMAgPIE_BMSWAS_Price}
+\title{readMAgPIE_BMSWAS_Price}
+\usage{
+readMAgPIE_BMSWAS_Price()
+}
+\value{
+The MAgPIE BMSWAS price data as a magpie object.
+}
+\description{
+Read annual regional bioenergy prices prepared from a MAgPIE report for use
+as OPEN-PROM's historical BMSWAS fuel price. The source file is already in
+OPEN-PROM region and subsector space and uses kUSD2015/toe.
+}
+\examples{
+\dontrun{
+x <- readSource("MAgPIE_BMSWAS_Price")
+}
+
+}
+\author{
+Songmin Yu
+}
diff --git a/man/toolReplaceBMSWASPrice.Rd b/man/toolReplaceBMSWASPrice.Rd
new file mode 100644
index 0000000..e3c0e93
--- /dev/null
+++ b/man/toolReplaceBMSWASPrice.Rd
@@ -0,0 +1,18 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/toolReplaceBMSWASPrice.R
+\name{toolReplaceBMSWASPrice}
+\alias{toolReplaceBMSWASPrice}
+\title{Replace aggregated BMSWAS prices with MAgPIE prices}
+\usage{
+toolReplaceBMSWASPrice(x)
+}
+\arguments{
+\item{x}{Regionally aggregated IFuelPrice magpie object.}
+}
+\value{
+IFuelPrice as a quitte data frame with BMSWAS values replaced.
+}
+\description{
+Replaces only existing BMSWAS region-SBS-year values. The MAgPIE source is
+expressed in kUSD2015/toe, while IFuelPrice is written in USD2015/toe.
+}